Patent Publication Number: US-2013241935-A1

Title: Computer implemented methods for generating engraved images for works of art

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to and hereby incorporates by reference U.S. Provisional Patent Application Ser. No. 60/931,462 filed on May 23, 2007. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates generally to printmaking engraving and more specifically to software for creating printmaking engraving. 
     2. The Prior Art 
     Engraving is the practice of incising a design onto a hard, flat surface, by cutting grooves into it. The result may be a decorative object in itself, as when silver or gold are engraved, or in art may provide an intaglio printing plate in printmaking of copper or another metal. 
     Traditional engravers use a hardened steel tool called a burin to cut the design into the surface, most traditionally a copper plate. Gravers come in a variety of shapes and sizes that yield different line types. The burin produces a unique and recognizable quality of line that is characterized by its steady, deliberate appearance and clean edges. The angle tint tool has a slightly curved tip that is commonly used in printmaking. Florentine liners are flat-bottomed tools with multiple lines incised into them, used to do fill work on larger areas. Flat gravers are used for doing fill work on letters, as well as most musical instrument engraving work. Round gravers are commonly used on silver to create bright cuts (also called bright-cut engraving), as well as other hard-to-cut metals such as nickel and steel. Burins are either square or elongated diamond-shaped and used for cutting straight lines. Other tools such as mezzotint rockers, roulets and burnishers are used for texturing effects. 
     Traditionally, engravers created darker areas by making an area of many very thin parallel lines (called hatching). When two sets of parallel line hatchings intersected each other for higher density, the resultant pattern was known as cross-hatching. The modern discipline of hand engraving survives largely in a few specialized fields. In most of industrial uses like production of Intaglio plates for commercial applications hand engraving was replaced with milling using CNC engraving/milling machines. 
     Another application of modern engraving is found in the printing industry. There, every day thousands of pages are engraved in rotogravure cylinders, typically a steel base with a copper layer of about 0.1 mm in which the image is transferred. After engraving, the image is protected with an approximately 6 μm chrome layer. Using this process the image will survive million plus copies in high speed printing presses. 
     Typically the image is created in some PDF-like format and enters a workflow where it is processed and automatically imposed to the huge printing cylinders. Today up to 192 pages can be engraved on the same cylinder. Since the cylinder serves to print one color, four cylinders are typically used to print one side of the substrate. Rotogravure has a major share in publication, packaging and decorative printing. Gravure cylinders are typically engraved digitally by a diamond tipped or laser etching machine. 
     Engraving machines such as the K500 (packaging) or K6 (publication) by Hell Gravure Systems use a diamond stylus to cut cells. Each cell creates one printing dot later in the process. A K6 can have up to 18 engraving heads each cutting 8.000 cells per second to an accuracy of 0.1 μm and below. They are of course fully computer controlled and the whole process of cylinder making is fully automated. Laser engraving machines are also in use. 
     Laser engraving is the practice of using lasers to engrave or mark an object (it is also sometimes incorrectly described as etching, which involves the use of acid or a similar chemical). The technique can be very technical and complex, and often a computer system is used to drive the movements of the laser head. Despite this complexity, very precise and clean engravings can be achieved at a high rate. The technique does not involve tool bits which contact the engraving surface and wear out. This is considered an advantage over alternative engraving technologies where bit heads have to be replaced regularly. 
     The impact of laser engraving has been more pronounced for specially-designed “laserable” materials. These include polymer and novel metal alloys. 
     A laser engraving machine can be thought of as three main parts: a laser, a controller, and a surface. The laser is like a pencil—the beam emitted from it allows the controller to trace patterns onto the surface. The controller (usually a computer) controls the direction, intensity, speed of movement, and spread of the laser beam aimed at the surface. The surface is picked to match what the laser can act on. 
     There are three main genres of engraving machines: The most common is the X-Y table where, usually, the work piece (surface) is stationary and the laser moves around in X and Y directions drawing vectors. Sometimes the laser is stationary and the work piece moves. Sometimes the work piece moves in the Y axis and the laser in the X axis. A second genre is for cylindrical work pieces (or flat work pieces mounted around a cylinder) where the laser effectively traverses a fine helix and on/off laser pulsing produces the desired image on a raster basis. In the third method, both the laser and work piece are stationary and galvo mirrors move the laser beam over the work piece surface. Laser engravers using this technology can work in either raster or vector mode. 
     The point where the laser (the terms “laser” and “laser beam” may be used interchangeably) touches the surface should be on the focal plane of the laser&#39;s optical system, and is usually synonymous with its focal point. This point is typically small, perhaps less than a fraction of a millimeter (depending on the optical wavelength). Only the area inside this focal point is significantly affected when the laser beam passes over the surface. The energy delivered by the laser changes the surface of the material under the focal point. It may heat up the surface and subsequently vaporize the material, or perhaps the material may fracture (known as “glass” or “glass up”) and flake off the surface. This is how material is removed from the surface to create an engraving. 
     SUMMARY OF THE INVENTION 
     Accordingly, computer software is provided that facilitates the creation of engraved or woodcut appearing illustrative images. The software provides various features and tools that allow a user to create an engraved image from a preexisting digitized image. More specifically, the software allows a user to overlay the engraved image upon the digitized image in a manner that allows the user to create an accurate reproduction in engraved form of the digitized image. 
     A software program according to the present invention provides coordinated image views by allowing a single computer input, such as a key stroke or mouse, pen or stylus click to switch the computer image representation viewed on a monitor between a photo view, an engraved view, and a composite merged view, which merges and overlays the photo view and the engraved view. When switching between the views, the images are synchronized so that each image is displayed at the same zoom level and pan position. Thus, changing the zoom or pan on one image causes the same to be done for all images. 
     The software also provides visually distinguished image merging by utilizing color to distinguish the overlay views. As such, the original photographic image is displayed in the photo view in a manner in which the light areas of the image are displayed in a pale yellow color and the dark areas of the image are displayed in a deep blue color. 
     In another embodiment, each engraved line is displayed as a solid black line painted on a solid white background line of slightly larger width. The average value of the combined lines represents a corresponding luminance value for each point on the line. 
     In another embodiment, engraved lines are prevented from being made too small or too close together Thus, the dynamic range (white to black) of the luminance levels in an engraved image are restricted from about 95% (representing white) to about 5% (representing black). 
     In still another embodiment, the software automatically creates narrow lines in the lighter areas of the image and wider lines in the darker areas of the image. The pressure data for each point along the scribe line can be manually entered using pen pressure, pen tilt, or pen orientation. The pressure data can also be determined by the software, based on the unique luminance of each pixel over which the scribe line is drawn. Pressure data here corresponds to a pressure that a person would have to use in a downward fashion while holding an actual engraving tool while engraving an image on an engraving plate. The greater the pressure used with the cutting tool, the wider and deeper the mark and the more ink the mark will hold for transfer to the paper. Thus pressure corresponds ultimately to the width of the engraved line. This last approach is easiest and best for most scribe lines. Manual entry of data is also available but is best for creating points of focus in the engraving. 
     In yet another embodiment, the software provides one or more “brushes” to facilitate the creation of engraved or woodcut appearing illustrative images. For example, an “engrave and burnish” brush is provided to erase any previously engraved line under the affected area of a new engraved line. An “engrave between lines” brush provides engraving only where no other affected area of an engraved line exists. A “trace line” follows the affected area edge of a previously drawn line. “Masked area marking” allows a magic wand or masking brush to identify an area for engraved lines. Once masked, the software only allows engraved lines within the masked area. 
     The software provides for error condensation. Error condensation is essentially error diffusion, which is used in printing, in reverse. Instead of diffusing the quantization error when printing each pixel as is done in the error diffusion process, error condensation collects printing errors made by not engraving lines between other nearby engraved lines and including these errors in the “somewhat analog” calculated depth for each point on the engraved lines which are printed. These little gaps between engraved lines are visible in the merged view where portions of the pale yellow-blue luminescence image are still seen. 
     Thus, the software provides the tools necessary to produce engraved images that accurately portray digitized photographic images. In addition, each engraved image is individually created by the user such that no two engraved images will be exactly the same and allow the user to invoke his or her artistic talents into the creation of each engraved image. The software produces an engraved image and image data that can be utilized by existing engraving machines to produce an engraving on any capable medium. 
     The foregoing advantages and characterizing features will become apparent from the following description of certain illustrative embodiments of the invention. The above-described features and advantages of the present invention, as well as additional features and advantages, will be set forth or will become more fully apparent in the detailed description that follows and in the appended claims. The novel features which are considered characteristic of this invention are set forth in the attached claims. Furthermore, the features and advantages of the present invention may be learned by the practice of the invention, or will be obvious to one skilled in the art from the description, as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawings illustrate exemplary embodiments for carrying out the invention. Like reference numerals refer to like parts in different views or embodiments of the present invention in the drawings. 
         FIG. 1  is a display window on a computer screen showing a photo view of a subject for creating an engraved image in accordance with the principles of the present invention. 
         FIG. 2  is a display window on a computer screen showing a zoomed photo view of a subject for creating an engraved image in accordance with the principles of the present invention. 
         FIG. 3  is a display window on a computer screen showing a merged view when creating an engraved image in accordance with the principles of the present invention. 
         FIG. 4  is a display window on a computer screen showing an engraved view when creating an engraved image in accordance with the principles of the present invention. 
         FIG. 5  is a display window on a computer screen showing a completed engraved image created with the engraving software in accordance with the principles of the present invention. 
         FIG. 6  is a display window on a computer screen showing a merged view when creating an engraved image in accordance with the principles of the present invention. 
         FIGS. 7 ,  8 ,  13 ,  16  are close-up views of engraved lines created with the engraving software in accordance with the principles of the present invention. 
         FIGS. 9 ,  10 ,  11 ,  12 ,  14 ,  15 ,  17 ,  19 ,  21 ,  27 ,  28  and  40  are computer icons of the engraving software in accordance with the principles of the present invention. 
         FIGS. 18 ,  20  and  22  are close-up views of engraved lines to illustrate various deletion functions of the engraving software in accordance with the principles of the present invention. 
         FIG. 23  is a flow diagram of a method for identifying engraved line endpoints according to the principles of the present invention. 
         FIGS. 24A ,  24 B,  24 C and  24 D are views of engraved lines to illustrate a trace line function of the engraving software in accordance with the principles of the present invention. 
         FIGS. 25A and 25B  are views of engraved lines to illustrate another trace line function of the engraving software in accordance with the principles of the present invention. 
         FIGS. 26A ,  26 B and  26 C are views of an underlying image being marked with an area marking tool in accordance with the principles of the present invention. 
         FIGS. 29A and 29B  are views of an underlying image in which the marked area is being modified with the software in accordance with the principles of the present invention. 
         FIGS. 30A and 30B  are views of an underlying image in which an edge of a marked area is being traced with an engraving line in accordance with the principles of the present invention. 
         FIGS. 31A and 31B  are views of an underlying image in which an engraving line is being excluded from the marked area in accordance with the principles of the present invention. 
         FIG. 32  is a display window on a computer screen of a preferences dialog box for controlling certain parameters of the software in accordance with the principles of the present invention. 
         FIGS. 33 ,  34 ,  35 ,  36 ,  37 ,  38  and  39  are merged views showing engraved lines over an underlying image to illustrate the effects on lines and trace lines as a function of changes in the preferences dialog box in accordance with the principles of the present invention. 
         FIG. 41  is a schematic flow diagram of a software program for generating an engraved image in accordance with the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following provides a detailed description of the invention for software for creating classical printmaking engravings. As illustrated in  FIG. 1 , a display window  10 , as displayed on a computer monitor (not shown) displaying photo view of a digital image  12  is illustrated in which the image  12  has been loaded onto the computer and opened by software according to the principles of the present invention. The image  12  has been selected by a user in order to generate an engraved image thereof using the image  12  as the basis for the engraved image. When the image  12  is first opened, the software will display the image  12  in a zoomed-out state to show the entire image  12  as illustrated. The image  12  may be a color photograph or other image. Whenever the pointing device  14  is moved over the image  12 , the cursor  14  automatically changes to a magnifying glass as shown. If the user clicks with a computer mouse or other computer input device, such as a pen or stylus, anywhere in the zoomed-out image  12 , the software will automatically zoom-in on the image  12  at the pixel level and pan the zoomed-in display so that the image  12  is centered where the user clicked. The photo view of the image  12  is displayed whenever the user hits a particular computer key that is configured by the software to operate as a “hotkey,” such as the ‘F1’ key, or if the user clicks on the first (left most) icon  16  using a pointing device in a window-based operating system, such as Microsoft Windows or Mac OS. The zoomed out view may be displayed anytime the user hits another hotkey, such as ‘F4’, or the user clicks on an icon  18 , such as the fourth icon from the left. 
     As illustrated in  FIG. 2 , when the user clicks on the image  12  shown in  FIG. 1 , e.g., on the bridge of the nose of the subject shown in  FIG. 1 , the software zooms in on the image  12  to magnify the image  12  to allow the image to be more easily converted into an engraved image. Thus, a zoomed in view of the photo view is displayed in color, if the image  12  was in color. Scroll bars  20  and  22  are provided to allow a user to pan the image within the display window  10 . 
     As shown in  FIG. 3 , when the user selects another hotkey, such as ‘F2’, or selects the second icon  23  at the upper left hand corner of the display window  10 , the “merged view” is displayed. At first before any etched lines have been created, the merged view will be the same as  FIG. 2 , but with the darker areas  24  converted by the software to shades of blue and the lighter areas  26  converted by the software to shades of yellow. To do so, the RGB pixel values are set so that red equals green which equals the luminance level for the original photo and the blue value for all pixels is set to a fixed value equaling approximately forty-three percent of full blue. Because red and green account for approximately eighty-nine percent of the luminance variation in a RGB computer monitor displayed image, the corresponding luminance variations in the yellow-blue representation of the photo range from ninety-four percent luminance corresponding to the whitest parts of a photo view to five percent luminance corresponding to blackest parts of a photo view. By converting the original photo, whether originally in color or in grayscale, to a high contrast, two color image, the user can readily see where darker areas  24  of the image will require more and/or thicker engraving lines  28  and where thinner or fewer engraving lines  30  will be appropriate in the lighter areas  26 . It has been found in accordance with the present invention to generate the underlying photo  25  into the two colors of blue and yellow, with the color blue filling in the darker areas  24  of the photo  25  and the lighter areas  26  being filled with the color yellow. Of course other contrasting colors may be employed. By providing the base image or photo  25  in yellow and blue, the etched lines  28 , which comprise visible line portions in the form of black lines  32  surrounded by white space boarders  34 , the white boarders  34  creating the “affected area”  36  of each etched line  32 , can be easily seen by the user when the etched lines  28  overlay the converted photo  25  in the merged view as shown. Thus, as represented in  FIG. 3 , the merged view displays a pale yellow-blue luminance version of the photo view with the engraved lines  28  displayed on top of the pale yellow-blue luminance photo  25 . The user uses the pointing device  40 , as is moveable by use of a computer mouse, pen and tablet, track ball or other similar peripheral devices known in the art connected to a computer running the software of the present invention to continue to add additional engraving lines  28 . 
     By employing black engraving lines, detail for engraving in the blackest part of the image is still possible because details can be observed there. The merged view is generated by first creating the yellow-blue luminance image to the display memory and then by generating the engraved view on top of the same display memory. Each engraved line is displayed as a solid black line painted on a solid white background line of slightly larger width. The average value of the combined lines can be used to represent a corresponding luminance value for each point on the line. Physical limitations of printing engraved images also can restrict the maximum dynamic range of rendered luminance values. Engraved lines are thus prevented from being made too small so as to not have the ability to accept the physical pigments of the ink or so small that the ink will not remain wet. In addition, the engraved areas are prevented from being wholly removed for a large area that would otherwise cause the media to be printed with the engraved image to bottom out into the void when printing. Thus, the dynamic range (white to black) of the luminance levels in an engraved image can be restricted to a range of about 95% (representing white) to about 5% (representing black). With corresponding dynamic ranges for both images, one image will be less likely to dominate over the other image. 
     As shown in  FIG. 4 , the engraving marks or lines  28  are continued to be added to the merged image shown in  FIG. 3  with various software tools (as will be explained in more detail). By pressing a hotkey, such as the F3 key on a computer keyboard (not shown) or selecting the third icon  46 , an engraved view  48  is created. The engraved view  48  only displays the engraved lines  28  that have been generated by the user and/or software. Since the engraving marks or lines  28  are shown in black, when the underlying photo is removed from view, only the engraved lines  28  are visible. By utilizing a white background  44  the white affected areas  36  (shown in  FIG. 3 ) blend into the background  44 . When switching between views, the software may be configured to preserve the same pan location and zoom of the photo, merged and engraved views. As such, the user can quickly select between each of the views, such as the original photo view and the engraved view to compare the engraving lines to the original image, for example. This allows the user to easily visualize the quality, position and visual effect of the engraved lines in representing the original photo. 
     As shown in  FIG. 5 , once the user has created a number of engraved lines  28 , the user can review their progress by viewing the entire engraved image  50 . The image  50  has been zoomed out and then the third icon  46  has been selected. The user can continue to add engraving lines  28  until the user is satisfied with the result as shown in  FIG. 5 . By allowing the user to input individual lines  28  with the input device, such as a computer mouse, tablet and pen or stylus or other input device, the user can insert his or her own artistic talents and style into the finished product such that no two engravings would be exactly the same to create individual works of art. The finished engraving  50  can then be printed or the stored data file can be used by existing engraving machines to engrave the image into a suitable material, such as copper plate, wood, plastic or other suitable materials known in the art. The data file can also be used to print out directly. The data file can also be used directly for display. 
     The software is configured with various engraving tools for creating engraved lines having various values that alter the line thickness, affected area, etc. Referring to  FIG. 6 , is a merged view  60  generated by selecting the icon  23  in which an engraved line  52  has been created by using an engraving value tool selected by clicking on the engraving value tool icon  62  or pressing a hotkey on a computer keyboard (not shown), such as F5. Using the engraving value tool icon  62  and drawing the line using the computer input device, as by pressing a mouse button and moving the mouse in a direction corresponding to the desired line direction represented in the merged view  60 , engraved line  52  is created. Note that the line parameters can be initially controlled by the user. In this example the line preferences have been set to six pixels, such that each line is drawn at an effective line width of six pixels. This allows the user to generate finer engravings by universally setting the line width to a lower pixel counts to generate thinner lines or to generate more coarse appearing engravings by increasing the effective line width. 
     By using the engraving value icon  62  and resulting engraving tool, engraved lines having computer controlled characteristics can be generated such that the black portions of the lines  52  are thicker in darker areas  64  of the underlying photo or image  12  and thinner in lighter areas  66 . Thus, the width of the black portion of the engraved line  52  is a function of the luminance value  68  of the pixels under each point, represented in X and Y positions  69  and  70 , of the engraved line  52 , the number of which is shown in display value window  72 . Accordingly, in this mode, dark areas  64  of the image create wider black portions in the engraving lines  52 , while lighter areas  66  of the image  12  generate more narrow black portions in the engraving line  52 . 
     To provide the user with information regarding the underlying value of each line, the tool bar  74  provides the line data in real time. The user will know the particular engraving mode since it is displayed on the tool bar  74 , shown as “Engraving (Value)” in this example. The current X position  69  (shown as “X: 1498”), Y position  70  (shown as “Y: 1682”), luminance  68  (shown as “Lum: 82”) and line number  72  (shown as “Line: 0”). Each icon provides a graphical indicator of the particular viewing mode or tool being used. For example, the icon  62  may include a representation of a colored image, such as green, under a colored engraving tool, such as yellow, indicating that selecting the icon  62  will result in displaying the merged view which shows both the converted underlying image and the previously created engraved lines. 
     As shown in  FIG. 7 , intersecting engraved lines  80  and  81  are illustrated. The engraved lines  80  and  81  intersect at approximately right angles. To create the lines  80  and  81 , the engraving value tool, as previously described, was used. Thus, the width W of the black portion  82  of the engraved line  80  is determined as a function of the luminance value of the pixels  84  and  92  under each point of the engraved line  80 . Likewise, the black portion  83  of the engraved line  81  is a function of the luminance value of the pixels  84  and  90  under each point of the engraved line  81 . Variations of line width W are evident in the lines  80  and  81  as they cross over pixels in darker area  87 , shown with representative darker pixels  84  which could fill the entire area  87  or at least the portion beneath the black portions  82  and  83  of the lines  80  and  81 , respectively, as compared to lighter areas  86  and  88 , shown with representative lighter pixels  90  and  92 , respectively, which would fill at least areas  86  and  88  that are beneath the black portions  82  and  83 . Thus, as the lines  80  and  81  pass from darker area  87  to lighter areas  86  and  88 , the width of the black portions  82  and  83  of the lines  80  and  81 , respectively, the software controls the width changing it from thicker (over the dark area  87 ) to thinner (over the light areas  86  and  88 ). Note, however, that in this mode the affected areas  97  and  98  of each line  80  and  81 , respectively, has the same width regardless of the width W of the black portion of each line  80  and  81 . The engraved value lines  80  and  81  can thus overlap and are merged together such that one line does not dominate over the other line (i.e., one line does not appear to be positioned on top of the other line or otherwise interrupt the continuity of the other line). 
     In another mode of engraving, an engraving pressure tool may be selected by selecting the engraving tool icon  62  from the tool bar  74  (as shown in  FIG. 6 ) or by pressing a hotkey, such as F5. In this mode, as shown in  FIG. 8 , the width W of the black portion  102  of the engraved line  101  is a function of the physical pressure made by a user on a pen tip of a pen and tablet input device (not shown), such as a Wacom pen/tablet, while drawing the line  101 . As shown in  FIG. 6 , the pen tip pressure P value is also dynamically displayed in box  104  as well as in graphical form in the slider box  106 , which may include a blue slider bar  108  over a yellow background that increases and decreases simultaneously with the corresponding pen pressure. This way, the user can visualize the relative pen pressure from minimum (0) to maximum (999) on the tool bar in a manner that allows the user to judge the amount of pen pressure that may be appropriate for a particular etched line when compared to the luminance value of the underlying image  12 . Thus, referring again to  FIG. 8 , for a lighter area  110  with higher yellow content, the user can lighten the pressure on the pen to create etched lines with thinner black portions  112  and line thickness transitions  113  between thinner portion  112  and thicker portion  115 . Because the user controls the pen pressure and thus the line thickness, the black portion  102  of line  101  can be made wider in lighter portions  110  of the underlying image. Judging the line thickness as a function of pen pressure is visually aided by viewing the comparative amount of yellow to blue in the box  108  shown in  FIG. 6 . Accordingly, in the pressure engraving mode, heavy pen tip pressure will result in a wider black portion  102  of the engraving line  101  and light pressure will create thinner or more narrow segments in the engraved line  103  with variations of pressure in between creating a transition  113  between thick and think line portions. 
     Note that the pressure tool can be scrolled at any time between an underlying value input, a pen tip pressure input and a pen tilt input, in which the angle of the relative to the tablet determines the line width W. The user will know that the pressure engraving tool mode has been selected if the engraving tool icon  62  ( FIG. 9 ) includes a down arrow  63  next to the yellow engraving tool  65 . The icon  100  ( FIG. 10 ) has been changed to illustrate pressure and the text adjacent the line data box  72  states “Engraving (Pressure).” The software creates and stores engraving line pressure data derived from image data, pen pressure, tilt and/or pen orientation. 
     As in other engraving modes, engraved lines  101  and  103  drawn in the engraving pressure mode can form intersecting lines that cross at approximately right angles and in such a manner that the lines  101  and  103  appear to be blended together at their intersection. 
     In another engraving mode, an engraving tilt tool is selected by clicking on the engraving tool icon  62  or pressing a hotkey (e.g., “F5”). Repeated clicking of the engraving tool icon  62  will cycle through the various engraving tools that are available. In the engraving tilt mode, the width W of the black portion  102  of the line  101  is controlled by angling or tilting a pen stylus relative to a pen tablet, such as a Wacom pen/tablet. The angle of the pen stylus relative to the pen tablet surface determines the engraving line width. In a vertical or perpendicular pen stylus position, the engrave line width is maximized according to the set software parameters while angling the pen stylus at an angle, such as 45 degrees, relative to the surface of the pen tablet results in thinner engraved lines, again as determined by set software parameters, with variations in pen tilt resulting in corresponding variations in line width. The level of pen tip tilt is dynamically displayed while drawing in the slider box  106  on the tool bar  74  and is also numerically displayed in the “P: ###” field  104  on the tool bar  74 . The user will know if the engraving tilt mode has been selected since the icon  62  includes a red angle arrow  110  next to the yellow engraving tool  65  ( FIG. 11 ). In addition the icon  100  is changed to a tilt icon displaying a pen stylus  112  interposed between angle arrow  113  and  114  ( FIG. 12 ). The text adjacent the line data box  72  indicates, “Engraving (Tilt).” It should be noted that in both the pressure engraving mode and tilt engraving mode, the luminance value of the underlying image  12  does not modify the engraving line thickness. This allows for artist impression and individuality in creating engraved images without computer interpolation of line data based upon the luminance of the underlying image. As such, a user can create an engraved image based upon his or her own interpretations and artistic talents alone. For example, an artist using the pressure and/or tilt engraving modes could generate thinner lines over darker portions of the underlying image and generating thicker lines over the lighter portions of the underlying image to create a negative engraved image if desired. 
     Another type of engraving is shown in  FIG. 13 . While using the “burnish then engrave” tool, by selecting the burnish then engrave icon  121 , shown in  FIG. 6 , or pressing a “burnish then engrave” hotkey, such as F6, two intersecting lines  120  and  122  have been drawn. With the software controlling the line width W based upon the luminance of the underlying image and more specifically, as a function of the luminance value of the pixels under each point of the engraved lines  120  and  122 , darker areas  126  of the image creates wider engraving line portions  128 ,  129  and  130  while engraving over lighter areas  132  creates more narrow black portions  134  of the engraving line  122 . Again, the software provides various visual clues in the tool bar  74  that will let the user know the particular engraving mode and tool being used. For example, the icon  121  ( FIG. 14 ) has a green image  136  under a yellow engraving tool  65  overlying a burnishing tool  138 . Also, the icon  100  ( FIG. 15 ) has been changed to a colored photo icon. Moreover, the text adjacent the line data box  72  states, “Burnish then Engrave (Value).” 
     When the burnish then engrave tool has been selected, engraved lines, such as line  122 , that are drawn over previously drawn engraved lines, such as line  120  will cause the previous line  120  to be divided such that the new line  122  intersects the previous line  120  in a manner that allows the new line to be continuous, while causing the previous line to be split at the point of intersection of the two lines. This allows non-overlapping engraved lines to be drawn with new lines essentially cutting through any preexisting engraving lines. When a new line  122  passes over an existing line  120 , the affected areas  140 ′ and  140 ″ of the resulting line segments  120 ′ and  120 ″ are recalculated for each line segment  120 ′ and  120 ″ such that the intersecting ends of the resulting line segments  120 ′ and  120 ″ are spaced according the affected areas  140 ′ and  140 ″ from the engraving line  122  and its corresponding affected area  142 . Thus, engraved lines  122  created with the burnish then engrave tool do not overlap previously drawn lines. As such, when a line  122  created with the burnish then engrave tool crosses over an existing engraved line  120  (no matter what tool was used to create the existing line), the portion of the existing engraved line  120  (and its corresponding affected area  140 ) which would be under the new burnish then engrave line is automatically erased. Accordingly, the burnish then engrave value tool erases any portion of any previous engraved line it covers and converts the remaining line segments  120 ′ and  120 ″ into independent line segments. Essentially, the burnish then engrave tool first burnishes (erases) any previous lines along its drawing path and then engraves the new engraved line along the drawing path of the line  122 . 
     As with any of the engraving tools described herein, burnish then engrave lines can be created using a “value” parameter such that the luminance of the underlying image controls the line width or by using “pressure” or “tilt” input parameters as previously discussed. By repeated selecting the burnish then engrave icon  121 , the user can select between value, pressure and tilt inputs. The toolbar  74  will display the mode that has been selected by the user. 
     Yet another mode of engraving is shown in  FIG. 16 . While using the “engrave un-engrave” tool, by selecting the engrave un-engrave icon  150 , shown in  FIG. 6 , or pressing a “engrave un-engrave” hotkey, such as F7, two intersecting lines  152  and  154  have been drawn. With the software controlling the line width W based upon the luminance of the underlying image and more specifically, as a function of the luminance value of the pixels under each point of the engraved lines  152  and  154 , darker area  156  of the image creates wider engraving line portions  158 ,  159  and  160  while engraving over lighter areas  162  and  163  creates more narrow black portions  164  and  165  of the engraving lines  152  and  154 , respectively. Again, the software provides various visual clues in the tool bar  74  that will let the user know the particular engraving mode and tool being used. For example, the icon  170  ( FIG. 17 ) depicts an engraving tool  171  along side a crossed-out circle  172  that may be in red. In the luminance “value” mode, the icon  100  will be in the form of the colored photo icon ( FIG. 15 ). Moreover, the text adjacent the line data box  72  states, “Engrave un-engrave (Value).” 
     When the engrave un-engrave tool has been selected, engraved lines, such as line  154 , that are drawn over previously drawn engraved lines, such as line  152  will not intersect the previously drawn line  152 . Thus, the new engrave un-engrave (value) line is forced to jump over that portion of the previously drawn line  152  that the second line  154  crosses. The engrave un-engrave tool allows new lines to be drawn without affecting any preexisting lines in order to fill in new engraved lines within existing spaces formed by previously drawn engraving lines. This allows previously drawn line  152  to maintain its length, while causing the new line  154  to be split at the point of intersection of the two lines. This allows non-overlapping engraved lines to be drawn with new lines essentially being cut by any preexisting engraving lines. When a new line  154  passes over an existing line  152 , the affected areas  166 ′ and  166 ″ of the resulting line segments  154 ′ and  154 ″ are recalculated for each line segment  154 ′ and  154 ″ such that the intersecting ends of the resulting line segments  154 ′ and  154 ″ are spaced according the affected areas  166 ′ and  166 ″ from the engraving line  152  and its corresponding affected area  168 . Thus, engraved lines  154  created with the engrave un-engrave tool do not overlap previously drawn lines. As such, when the engrave un-engrave line  154  crosses over an existing engraved line  152  (no matter what tool was used to create the previous line), the portion of the existing engraved line  152  (and its corresponding affected area  168 ) which would otherwise be under the new engrave un-engrave line is maintained. Thus, the engrave un-engrave value tool erases any portion of any new engraved lines that would otherwise cover any existing engraved lines and converts the new line into multiple line segments  154 ′ and  154 ″. Essentially, the engrave un-engrave tool works oppositely to the burnish then engrave tool by erasing any newly created line portions that extend over previously drawn engraving lines. 
     As with any of the engraving tools described herein, engrave un-engrave lines can be created using a “value” parameter such that the luminance of the underlying image controls the line width or by using “pressure” or “tilt” input parameters as previously discussed. By repeated selecting the engrave un-engrave icon  170 , the user can select between value, pressure and tilt inputs. The toolbar  74  will display the particular mode that has been selected by the user. 
     As engraving lines are created, there may be certain instances when certain lines or portions thereof are not desired. The software provides tools for removing previously drawn lines or portions thereof. Accordingly, two erasing tools are provided. The first, referred to as “burnish line,” allows the user to erase a portion of a previously drawn line. As shown in  FIG. 18 , six engraving lines  181 ,  182 ′,  182 ″,  182 ′″,  183 ′ and  183 ″ are shown. By selecting the burnish tool, either by pressing a hot key, such as “F8,” or by selecting the burnish tool icon  180  (see  FIG. 19 ) the user can selectively erase portions of one or more of the lines  183 ′ and  182 ′. Once the burnishing tool is selected, the text in the tool bar  74  will display “Burnish Line” and the pointing device will become a pressure sensitive brush. Using a pen tablet, the diameter of the brush is a function of pen stylus tip pressure, such that higher pressure results in a larger diameter brush. In order to erase portions of lines  183 ′ and  182 ′, a mark  184  is drawn across the line portions to be erased. The mark  184  begins at a first point  186  where pressure was first applied and continues along a path to a second point  187  where pressure is released. In this example, the pressure at point  186  was less than the pressure at point  187  resulting in a widening mark  184  between point  186  and point  187 . The mark may be in form of a semi-translucent mark, such as a pale blue mark, such that the underlying image as well as the lines  183 ′ and  182 ′ and  187  over which the mark  184  is applied are visible. 
     As shown in  FIG. 20 , when the user releases pressure form the tip of the pen stylus, of the pointing device, the software will automatically and immediately erase the portions  188  and  189  from lines  182 ′ and  183 ′ that were covered by the blue mark  184  shown in  FIG. 18 . The software converts the remaining engraving line fragments into individual engraving lines  183 ′,  183 ″″,  182 ′ and  182 ″″. As such, swaths of portions of engraving lines can be erased by clicking and dragging the burnishing brush over portions of engraving lines sought to be erased. 
     Referring again to  FIG. 18 , another mode of engraving line removal is illustrated. By clicking on the “Draw over Line to Erase” icon  180 ′ shown in  FIG. 21  or by pressing a hotkey, such as “F8,” until the icon  180  displays a pencil eraser and the text in the toolbar  74  states “Draw over Line to Erase,” the pointing device will allow a line  190  to be drawn. Note that this tool can be scrolled at any time between the burnish line tool and erase line tool and back by clicking on the icon  180  or by repeatedly pressing the appropriate hotkey. The erase line  190  has been drawn over the top of two of the lines  181  and  182 ″ in the image  192 . This new line is visually distinguishable from the existing engraving lines  181 ,  182 ′,  182 ″,  183 ′,  183 ″ and  183 ′″ because it has no white affected area surrounding it. The line  190  will be visible to the user until the user releases pressure from the pen tip of the pointing device. As shown in  FIG. 22 , when the pen tip pressure is released, the engraving lines  181  and  182 ″ that were marked by the erase line  190  are completely erased. All other engraving lines  182 ′,  182 ″,  183 ′ and  183 ″ are unaffected and remain undisturbed in the image  192 . 
     When drawing engraving lines as previously described it may be desirable to link new lines to previously drawn lines. The software according to the present invention allows lines to be connected to the nearest endpoint of existing lines. By pressing the “Ctrl” key, for example, at the beginning of drawing any engraving line causes the beginning of the new line to search for the nearest endpoint of a previously drawn engraved line and connects the new line to the existing line endpoint as though the combination of lines were to become a single continuous line. Pressing the “Ctrl” key at the end of drawing an engraved line will cause a search for the nearest endpoint of a previously drawn engraved line and connect the new line to the existing line as though the lines were a single continuous line. The search is arbitrarily limited to the value entered in the “Preferences” dialog for “Pixels between Traced Lines,” as will be discussed in more detail herein. If the software search does not find an endpoint within the pre-specified radius, the new engraving line will begin or end at the current pointing device location. The “Ctrl” key begin and end feature works for all engraving tools including the burnish then engrave tool and the engrave un-engrave tool previously discussed. 
     This process  200  is illustrated in  FIG. 23 . When the start or end of an engraved line has been activated  202 , the software will determine  204  whether the “CTRL” key has been pressed. If not, the software will cause  206  the line to start or end, as the case may be, at the current pointing device position. If so, the software will search  208  for the nearest preexisting engraving line endpoint in the image. If the software determines  210  that an endpoint of a preexisting line is within the preset radius, the lines will be automatically connected  212  at their respective endpoints. 
     If the “Ctrl” key is pressed during the drawing of a line, the line will rubber band from the point at which the “Ctrl” key was first pressed and then snap to that point where the “Ctrl” key is released. If the “Alt” key is pressed during the drawing of a line, the pen or other input device, can be lifted and tapped to create a series of points. When the “Alt” key is released, the engraving line will resume in the normal drawing mode as the next point the pen begins to drawn. The series of points created are then used to create a poly Bèzier curve and connect the piece-wise drawing segments as though they were a continuation of the poly Bèzier curves. It is noted that while reference has been made to specific keys for performing the foregoing functions, it is contemplated that other keys could be programmed to perform these functions without departing from the spirit of the present invention. 
     Another form of engraved images uses trace lines in which the engraved lines appear to be in parallel over portions of the image. This is at least in part the type of engraving used on United States paper currency and is different from the engraved image created with random engraved lines as shown in  FIG. 5 . As shown in  FIG. 24A , a first engraving line  220  has been drawn wherein the line is shown in black and the affected area  222  of the engraved line is shown in white. As previously discussed, areas of the image in the merged view that have no engraving marks appear as a pale yellow-blue image. Note that the trash can icon shown in  FIG. 6  has no cyan color in it. This indicates that no areas of the merged image have been made into marked areas. By selecting the trace line tool, which can be chosen by the user by clicking on the icon  225  or pressing the appropriate hotkey, such as the “F9” key, the pointing device becomes a pressure sensitive brush wherein the brush diameter is a function of pen stylus pressure. If there are no marked areas in the image, the software will automatically create marked areas to surround all existing engraving lines. The marked areas  227  extend outward from the center of the engraved lines by the value given in “Pixels Between Traced Lines” in the preferences menu. These new marked areas  227  (which have been automatically created) are shown as a cyan colored area surrounding each engraving line. 
     Once the trace line tool has been selected, the user can create a mark  224  as shown. The trace mark  224  will appear as a translucent blue having a width determined by the pressure applied to the pen stylus. By tracing the line  220  along one side thereof, the software is instructed to create a trace line  226 , as shown in  FIG. 24B  adjacent and somewhat parallel to the first line  220  along the side of the line  220  where the mark  224  was created. That is, the second line  226  traces the first line  220 . The trace mark  224  will remain visible so long as the user maintains pressure on the pen stylus. As soon as the pressure is released, the software will determine that the trace mark  224  has been ended and will automatically generate the new trace line  226 . By repeating this process above and below the first line  220 , as shown in  FIGS. 24B and 24C , using the trace line tool, additional trace lines  228  are automatically created. Each trace line  230 , as shown in  FIG. 24D , may vary in width along its length depending on the luminance of the underlying image. Accordingly, the trace lines, when combined, create an engraved image that is based upon the luminance of the underlying image, in this example, the eye of a subject. Once the user selects a tool other than the trace line tool, the cyan color surrounding the engraved lines indicating the marked areas are automatically removed. The resulting “somewhat parallel lines” represent a typical classical engraving technique used by some engraving artists and differs from the “somewhat random lines” used in the image shown in  FIG. 5 . 
     A trace line brush mark  240  can also be used to create more than one trace line. As shown in  FIG. 25A , the trace line brush mark  240 , drawn over an existing engraved line  242 , straddles both sides of the engraved line  242 . The marked area  244 , which is different from the affected area  246 , is created when the trace line tool is first selected. The trace line brush mark  240  remains visible until the user releases pressure from the pen tip of the pointing device (not shown). A shown in  FIG. 25B , when the pen tip pressure is released, the software automatically creates trace line  248  above original engraved line  242  and trace line  249  below original engraved line  242 . These engraved lines  248  and  249  trace the first line. The second and third lines  248  and  249  are formed along the edge  250  of the marked area  244 . Once the new lines  248  and  249  are created, a new marked area  252  is also automatically created around the new engraved lines  248  and  249 . 
     The marked area  252  can be modified in the preferences menu by changing the value in the “Pixels Between Traced Lines.” For example, the “Pixels Between Traced Lines” could be set at six pixels, twelve pixels or any other number as desired. By increasing the pixels between traced lines, the separation between subsequently created, adjacent traced lines becomes larger resulting in engraved images that appear more coarse. Conversely, images created using the trace line tool where the pixel between lines has been lowered results in engraved images that appear more fine. For example to create a more coarse looking engraved image, the pixels per line could be set to 20 pixels per line, the pixels between traced lines set to 20 pixels, the maximum white width set to 20 pixels per line and the max/min line width ratio set to 10.0 in the preferences menu. For finer images, the pixels per line could be set to 6 pixels per line, the maximum white width set to 6 pixels per line and the max/min line width ratio set equal 10.0. 
     An important feature of the software of the present invention, referred herein as “marked areas,” enables the user to create more precise engraving lines within certain specified areas. By separating certain areas of the underlying image, the user can generate engraved lines along a defined edge of the underlying image, such as a visual edge created between light and dark areas of the underlying image, or within a specific area of the underlying image, such as within a predominately lighter area. As shown in  FIG. 26A , a portion of the underlying image  260  (the side of a subject&#39;s nose shown in the image  260 ) is highlighted. Such highlights resulting from brighter portions in the image  260 , which may be the result of ambient light reflections, are represented as pale yellow portions  262  in the merged view, while the darker areas  264  in the merged view are represented in shades of blue. When the image  260  comprises a photographic image, these light and dark areas  262  and  264  do not always have smooth or clean delineations between the light and dark areas  262  and  264 , especially when the subject image is not completely smooth, as is with the case of the face of a person. Thus, there may be darker pixels  266  that lie within the lighter area  262  near the transition between light and dark areas  262  and  264 . In addition, the transition line  268  may not be smooth or continuous. 
     The mark area tool can be selected by clicking on the icon  300  (see  FIG. 6  and  FIG. 27 ) or by pressing a keyboard hotkey, such as F11. The mark area tool icon  300  is a graphical representation of a paint can  302  in a tipped position with paint  304  being poured from the paint can  302 . Once this mark area tool is selected, a pressure sensitive brush, with the brush diameter equal to a function of pen stylus pressure, can be used to draw the brush mark  268 . Once selected, the text in the tool bar  74  will display “Mark Area.” The brush mark  268  appears as a light blue or white mark over the pale yellow/blue merged image so as to be easily visible. For illustrative purposes, the mark  268  has been drawn in the lighter area  262  of the underlying image  260 . Once drawn, the software connects all pixels having luminance values in the range of values under the marked area. The software selects all pixels around the brush mark  268  having luminance values in the range of values that are contained within the brush mark  268 . Once the connected area of pixels  262  having these values is determined, the remaining pixels  270  which are not connected are marked (i.e., highlighted) and displayed by showing them in a green hue. Also, the brush mark  268  is automatically erased. The green marked (highlighted) area  270 , which in this example, coincides with the darker areas  264  of the underlying image, can be thought of as pixels  270  which will not be processed in subsequent operations. The unmarked or normal area  271  which contains pixels having appropriate luminance values will be displayed in pale yellow so as to be easily visually distinguishable form the marked green area  270 . As such, the image  260  will change from the pale yellow/blue merged image into a pale yellow/green image where the yellow portion  271  will constitute the only portion of the image  260  where further operations can be performed until the user changes to a different mode. 
     Once the unmarked area  271  is created, various functions can be performed. As shown in  FIG. 26B , the user can now select the paint highlighted area tool icon  310  (see  FIG. 6  and  FIG. 28 ), which is in the form of a paintbrush  312 . This tool can be selected by clicking on the icon  310  or by pressing the appropriate hotkey, such as the “F12” key on a computer keyboard. When selected, the pointing device becomes a pressure sensitive brush, whereby the brush diameter is a function of pen stylus pressure. As shown in  FIG. 26B , the pixels  272  and  274  of the underlying image  260  that are contained within the boundary  276  of the brush mark  278  are shown in various shades of blue depending on the luminance of the underlying image  260 , while areas in pale yellow are displayed in white. By using the brush, the user can paint specific light blue pixels, such as pixels  272  and  274  that may be in an area where the user desires higher contrast between the light area  262  and the darker area  264 . The rest of the image  260 , outside the brush marked area are displayed in shades of green with the lightest portion  262  of the image  260 . 
     As shown in  FIG. 26C , when the pressure on the pen stylus is released, all of the light blue pixels, such as pixels  272  and  274  in the brush marked area  278  shown in  FIG. 26B  are deleted from the marked (highlighted) area  278 . Any pixels  273  and  275  which were previously marked green (highlighted) under the brush mark  278  have now turned back to the normal pale yellow-blue of the normal merged image. In this example, the purpose of the paint highlighted area tool used in the unmarked area  271  is to create a smooth edge  280  in the marked area boundary  281  on the ridge of the nose. Note that the paint highlighted area tool decreases the marked (highlighted) area  270 . 
     Another function that can be performed when a marked area  270  has been created is the burnish highlighted area tool, which is automatically selected when the burnish tool icon  180  (see  FIGS. 6 and 19 ) is selected in the marked area mode or by pressing a hotkey such as “F10.” When the burnish tool is selected, the pointing device becomes a pressure sensitive brush where brush diameter is a function of pen stylus pressure. In the burnish highlighted area mode, the user can paint the bright yellow pixels, such as pixels  282  and  284  with this brush. The brush mark  286  will appear as a bright yellow streak over the pale yellow and green pixels of the underlying image. 
     As shown in  FIG. 29B , as soon as pressure from the pen tip is released, all of the bright yellow pixels in the brush marked area  286  of  FIG. 29A  have been excluded from the unmarked area  271  and thus processed as indicated by the fact that they are now highlighted by being painted green. In this example, the purpose of the burnish highlighted area tool in the unmarked area  271  is to create a smooth boundary edge  288  between the unmarked area  271  and marked area  270  in the shadowed area to the right of the nose  290 . The burnish highlighted area tool increases the marked (highlighted) area. 
     Referring again briefly to  FIG. 26C , if a user desires to create a trace line along the edge  280  of the marked boundary  281 , the user can select the trace line tool by clicking on the trace line tool icon  225  (see  FIG. 6 ) or hot key F9. When selected, the bright green pixels of the marked area  270  became paler green. As previously described with use of the trace line tool, the pointing device becomes a pressure sensitive brush with brush diameter equal to a function of pen pressure. As shown in  FIG. 30A , the user can then paint the blue pixels shown in along the edge  280  by creating a brush mark  324 . The brush mark will appear to have a blue portion  326  over the dark pixels of the underlying image  260  and a white portion  328  over the yellow highlighted area  271 . 
     As soon as the pressure on the pen stylus is released, any pixels  320  and  322  that were painted blue within the unmarked area  271  and that were contained within the brush mark area  324  (i.e., on the boundary between the unmarked area  271  area (displayed in yellow) and the marked or excluded area  270  (marked or highlighted in light green) become part of a newly engraved trace line  330 . As such, by creating the marked area  270  and creating an edge  280  between the marked and unmarked areas, an outline of an object or feature can be quickly generated. 
     As shown in  FIGS. 31A and 31B , a user can select the engraving pressure tool previously discussed in the marked area mode. Doing so, allows the user to create engraving lines that will only be generated within the normal or unmarked area  271 . Using the engraving line tool, the user can draw a line  331  diagonally from the right eye to the left side of the nose as illustrated. In the marked area mode, the line  331  is blue in color depicting heavy pressure whereas light pressure is otherwise indicated by a black line. Note that the line  331  crosses both marked (highlighted) areas  270  and normal unmarked areas  271 . 
     As further illustrated in  FIG. 31B , as soon as the user releases pressure from the pen tip of the pointing device, the software immediately discards all portions of the line  331  that are outside the normal area  271 . The software also converts that portion of the line  331  within the normal area  271  to a simulated engraved line using the pressure data recorded by the software. Because of the heavy pressure used, the resulting engraved line  331  is darker than the other engraved line  330  that was lighter because the line  330  was created based on the underlying image luminescence. Accordingly, by using image area marking as herein described, the user can create specific areas  271  within the image  260  within which engraving will only be allowed. Thus, any lines or portions of lines drawn in the marked (highlighted green) area  270  are excluded and eliminated. 
     As shown in  FIGS. 6 and 40 , the user can select a small trash can icon  350  by clicking or using hotkey Ctrl+F1. The icon depicts a small trash can  352  which is filled with an area  354  with the color blue. If the pointing device is held momentarily over any icon, a button hint typically displays. For the icon  350 , the hint will display, “Erase the highlighted area completely.” Clicking the icon  350  will remove the marked area from the image  260  and return the software to the merged view previously selected. Thus, all marked areas previously highlighted are erased. The Merged view goes back to the normal pale yellow-blue display with any engraved lines shown in black with corresponding white affected areas surrounding each engraved line. Also the small trash can icon  354  previously filled with the color blue has been emptied of the blue color to indicate that software is no longer in the marked area mode. Any time there is a marked area, the blue color area  354  is shown in the trash can  352 . Also, the software is configured such that only the merged image view will show marked areas. Marked areas are not visible on the photo view or the scribed view. 
     In order to help fill areas between engraved lines that may not be completely filled manually by creating individual engraving lines, the software may by selecting the error condensation icon  370  shown in  FIG. 6 , which is in the form of a curved arrow, or pressing “Ctrl+F2” on a computer keyboard. Error condensation is a special filter algorithm used by the software that is available when the variable line width radio button has been selected for engraving variations in the preferences dialog. 
     The error condensation filter can be applied to a marked area if a marked area has been identified or to the entire image if no marked area has been identified. The error condensation filter can be applied in various degrees by using the “+” and “−” keys on a computer keyboard and then applied by pressing the “Enter” key. Typically, the user will view the engrave view while determining the level of filtering to apply. The Engraved view is modified in real time as the filter is adjusted so that the user can see the level of error condensation being applied and adjust the error condensation accordingly. 
     The error condensation filter can be thought of as applying an error diffusion algorithm in reverse. Instead of diffusing the quantization error, as some printers do when printing each pixel, error condensation collects printing errors that would otherwise be made as a result of engraving lines not being present between other nearby engraved lines and including these errors in the “somewhat analog” calculated depth for each point on the engraved lines that are printed. Such small gaps between engraved lines are visible in the merged view where portions of the pale yellow-blue luminescence image are still visible to show the user that the engraved lines and their surrounding affected areas are spaced apart. 
     Each point on an engraved line can be enlarged or reduced according to values entered in the preferences selections. When a physical scribe is pressed harder into a copper engraving plate, it leaves a deeper and wider indentation. The bigger the indentation in the physical printing plate, the more ink it holds and the bigger the printing mark transferred to the printed media. When using a pen stylus to create engraved lines, the software records the pressure made for each point of the engraved line. These pressure points determine the physical width along the printed engraved line. The recorded pressure of each point is modified when using the error condense filter. 
     The error condensation algorithm calculates the distance to the nearest point on an engraved line for each pixel in the image. If the distance calculated is within the “error condensation radius limit” entered in the “Pixels Between Traced Lines” field of the preferences dialog, then the pixel is included in a calculation for the pressure to be applied at this nearest point. Points along an engraving line may require a greater pressure if there are no other nearby line points for these condensation errors to accumulate. End points of engraved lines or corners of engraved lines require these error condensation sums to be distributed somewhat towards the interior of the engraved line so as not to create bulbs on the ends of these lines or balloons at the corners of lines. The affect of the errors may also be diminished in the algorithm as the distance increases towards the “error condensation radius limit”. 
     As previously discussed, various settings and parameters of a particular engraved image are controlled in the preferences dialogue box and may be changed by the user.  FIG. 32  illustrates a preferences dialogue box  400  according to the present invention. For the each engraved image, a user may change the settings in the preferences dialog box  400 . The image file size for the current image displayed (and previously selected by the user) is reported in pixels including the pixels width box and pixels length box. 
     The output size can also be entered by the user both width (in inches and cm) and length (also in inches and cm). Entering any one of the output size values causes the other values to be calculated based on the pixel aspect ration of the current image displayed. Lines per inch, lines per centimeter, and pixels per line are interrelated and based on the pixels in the image and the output Size. A number entered in any one of these fields will cause the software to calculate the other fields based on the formula: Lines Per Inch=Pixels Width/Output Width/Pixels Per Line. By entering one of these numbers, the user can determine the level of detail in the final output. 
     When the maximum white width (pixels/line) is set to the same number as pixels per line then the total width (white+black) is a constant and is independent of engraving line variations based on image luminescence, pen pressure or pen tilt. When maximum white width is set to a number greater than the pixels per line, then the white space grows from the value set in pixels per line for the darkest engraving lines to the value set in maximum white width for the lightest engraved lines. The maximum line density coverage determines the maximum line width as expressed by the formula: Maximum Line Width=Pixels Per Line×Maximum Line Density Coverage. Large areas of the darkest printing still require some white space to preserve voids for ink. This number is used to create these white gaps between adjacent engraved lines. 
     The max/min line width ratio determines the dynamic range of variation allowed for the black line width. In classical engraving, the more engraving pressure that is applied to the scribing tool, the wider the resulting line when printed. The number entered here will determine the ratio of the widest line possible to the narrowest line possible as given by the formula: Ratio=Widest Line/Narrowest Line. The minimum value allowed is 1.0, which means that the black line width is a constant. In this case, the only indication of line variation is visible with the surrounding white width when and if the maximum white width is set to a number greater than Pixels Per Line. 
     The number entered for pixels between traced lines determines the separation (in pixels) when tracing between parallel lines. The number entered cannot be less than the pixels per line. The number entered here is also used for the error condensation radius limit. As the image is condensed onto the existing engraved lines, only errors within the pixel radius entered here will be condensed onto the existing engraved lines. The Minimum Line Length (in Pixels) determines the minimum length of an engraved line in terms of pixels moved while engraving the line. Engraved lines in the software which are determined to be less than the minimum line length are eliminated. The minimum line length is arbitrarily set to 2 pixels. By the choice of numbers entered in the max/min line width ratio and maximum white width, the user may select either variable (black) line width or variable line separation engraving styles. 
     The variable line separation engraving style uses a fixed black line width (which is equal to the pixels per line as described above). The white affected area surrounding the fixed black line width varies according to the underlying image, pen pressure, or pen tilt. For the variable line separation engraving style, the max/min line width ratio is set to 1.0 and the maximum white width to a number at least double the pixels per line. The variable line width engraving style uses variations of the black line width to vary within a fixed width white affected area. For the variable line width engraving style, set the max/min line width ratio to a number such as 10.0 and the maximum white width to equal the pixels per line. A combination of these engraving styles may also be used by setting the max/min line width ratio to a number greater than 1.0 and the maximum white width to a number greater than the pixels per line. 
     If the user changes the pixels per line to a number greater that the pixels between traced lines, the number set forth in the pixels between traced lines box will automatically be changed to the same number. 
       FIGS. 33 ,  34  and  35  illustrate the effect the line size parameter previously described in the preferences dialog box has on engraved lines  450  that are generated with the software. In  FIG. 33 , the pixels per line has been set to 6 pixels per line. The maximum white width is set to 6 pixels per line (for a variable line width style), the max/min line width ratio is set to 10.0 (for a variable line width style) and the pixels between traced lines has been set to 6 pixels between traced lines. As shown, each black engraved line  452  is surrounded by a white affected area  454  such that the ratio of white to black in mid shaded areas  457  in the underlying image  456  are approximately equal with the black portions  452  thickening in darker areas  457  and thinning in lighter areas  458 . The white affected areas  454  for each line  452  abut one another so that there are no gaps between affected areas and thus no portion of the underlying image  456  showing through the set of trace lines  450 . 
     The set of trace lines  460  in  FIG. 34  have been generated with at least one different line parameter in the preferences dialog box. In this example, the pixels per line remains at 6 pixels per line, the maximum white width remains at 6 pixels per line (for variable line width style) and the max/min line width ratio remains at 10.0 (for variable line width style). Pixels between traced lines, however, has been changed to 12 pixels between traced lines. Note how the set of traced lines  460  are each comprised of a black engraved line  462  surrounded by a white affected area  464  with the ratio of white to black in middle shades in the underlying image  456  approximately equal with the black portions  462 , the black portions  462  becoming somewhat thicker in darker areas  457  and thinner in lighter areas  458 . Because the pixels between traced lines, however, has been increased, gaps  466  are formed between adjacent affected areas such that the underlying image  456  is visible between adjacent engraved lines  460 . Essentially this allows the user to create traced lines that have more spacing between lines while maintaining the basic engraved line width. 
     In  FIG. 35 , the set of trace lines  470  have been created with the line parameters set with the pixels per line at 20 pixels per line, the maximum white width set at 20 pixels per line (for variable line width style), the max/min line width Ratio set at 10.0 (for variable line width style and the pixels between traced lines set at 20 pixels between traced lines. Accordingly, as in  FIGS. 33 and 34 , each black engraved line  472  is surrounded by a white affected area  474  such that the ratio of white to black in middle shades in the underlying image  456  are approximately equal with the black portions  472  thickening in darker areas and thinning in lighter areas. Also, the white affected areas  474  for each line  472  abut one another so that there are no gaps between affected areas and thus no portion of the underlying image  456  showing between the set of trace lines  470 . The trace lines  470  have increased in width with a corresponding increase in affected area  474 . Thus, the resulting engraved image will have a more coarse appearance compared to the engraved image resulting from engraved lines  450  which will have finer detail. At any time during the course of producing the engraved image, the user can access the preferences dialog box and change the line parameters to change the line characteristics, such as changing the overall width of the lines being drawn from thinner lines to thicker lines and back. 
     In the previous examples shown in  FIGS. 33 ,  34  and  35 , the engraved line thickness changed based upon the luminance of the underlying image to create black and white contrasts to recreate the underlying image. Another form of engraving is illustrated in  FIGS. 36 ,  37 ,  38  and  39  in which the width of all black portions of engraved lines is fixed along the length of each line. The white affected areas, however, and thus the spacing of the black lines, varies according to the underlying image luminance, pen pressure or pen tilt (depending on the current engraving mode) to create variable line separation. The fixed black line width is equal to the pixels per line entered in the preferences dialog box. 
     For example, as shown in  FIG. 36 , the maximum white width has been set to 15, the pixels between traced lines set at 6 and the max/min line width ratio set to 1.0. Using these settings an arbitrary line  480  across the facial image  482  using a luminance (value) based engraving tool. Accordingly, the width of the black portion  484  of the engraving line is fixed. The width of the surrounding white affected area  486  of the engraving line  480  varies. In dark portions  487  of the image, the surrounding white area  486  is narrow. In light portions  488  of the image  482 , the surrounding white area  486  is wider. 
     As shown in  FIG. 37 , employing the use of the trace line tool previously described, a plurality of somewhat parallel lines  480 ,  481  and  483  can be created, based on the first line  480  shown in  FIG. 36 . In this mode, the width of the black portions  484 ,  485  and  489  of all engraving lines  480 ,  481  and  483 , respectively, are fixed in width while the width of the surrounding affected white areas of the engraving lines  480 ,  481  and  483  vary. Also, the lines  480 ,  481  and  483  bunch together in the dark portions  487  of the image where the surrounding white areas are narrow. In light portions  488  of the image  482 , the surrounding white areas  484 ,  485  and  487  are wide and the lines  480 ,  481  and  483  become spread further apart. 
     A combination of the variable (black) line width and variable line separation engraving styles may also be used by setting the max/min line width ratio to a number greater than 1.0 and the maximum white width to a number greater than the pixels per line. For example, as shown in  FIG. 38 , an arbitrary line  500  has been drawn with the following set parameters: the pixels per line is set to 6, the maximum white width is set to 12, the pixels between traced lines set to 6, and the max/min line width ratio set to 5.0. The line  500  is created with a luminance (value) based engraving tool. The width of the black portion  502  of the engraving line  500  is not fixed in width and varies as a function of the underlying image  504  luminescence. In addition, the width of the surrounding white affected area  506  of the engraving line  500  varies. In dark portions  508  of the image  504 , the surrounding white area  506  is narrow and the black portion  502  widens. In light portions  510  of the image  504 , the surrounding white area  506  widens and the black portion  502  narrows. 
     As shown in  FIG. 39 , using the trace line tool as previously described to create additional lines  512  and  514  that are somewhat parallel to the first line  500 , the widths of the black portions  502 ,  516  and  518  of all engraving lines  500 ,  512  and  514  varies. In addition, the widths of the surrounding white areas  506 ,  520  and  522  of the engraving lines  502 ,  516  and  518  also varies. Thus, the lines  500 ,  512  and  514  bunch together in the dark portions  508  of the image where the surrounding white areas  506 ,  520  and  522  are narrow. In lighter portions  510  of the image  504 , the surrounding white areas  506 ,  520  and  522  are wider, the black portions  502 ,  516  and  518  of the lines  500 ,  512  and  514  become thinner and are more spread apart. 
     The software stores the engraved image data in pseudo-vector format. Using a mouse or a pen-tablet, the centerline of the computer-simulated stylus can be saved as engraving marks are made. If a pen-tablet is used, pressure data, tilt angle data or tilt orientation data can be saved corresponding to the x-y location of the scribe mark centerline. A unique number can also be assigned to each scribe line and to each pixel of the scribe-line centerline so that all of the pixels of the scribe line can be grouped together. Because the mouse or pen motion on the software client window surface is a series of x-y data points corresponding to the rasterized image surface, each of these points can be recorded with a number corresponding to the pressure to be applied to the stylus and a unique number corresponding to the scribe line number. From this data and stylus modeling data, the engrave view can be derived. Once the engraved view is derived, the merged view can be derived by combining it with the photo view data. The combination of x-y data, pressure data, and unique line number data are stored in a pressure file. The software stores the pressure data as an RGB bitmapped image. The red channel contains 8 bits (255 distinct levels) of stylus pressure data and the blue and green channels contain 16 bits (65535 unique numbers) of line number data. Pixels which have no line numbers or no pressure data are internally stored as black (R=0x00, G=0x00, B=0x00). Saving the engraved file as pressure data offers some unique advantages. It allows the modeled engraved view and merged view to be regenerated at any point in the design process. In addition, because a small engraved image may have 10,000 lines or more, a single line may be easily removed or edited at any time. Also, a pseudo-vector format can be smoothly enlarged using poly Bèzier curves with the raster x-y data. Furthermore, there are many existing vendors of rotary engraving equipment and laser engraving equipment that utilize vector drivers for their equipment that would be compatible with a pseudo-vector format, making the software compatible with existing engraving equipment. 
       FIG. 41  is a schematic flow diagram of the basic process steps of the software, generally indicated at  600 , according to the principles of the present invention. In order to produce an engraved image, the software allows the user to open  602  a digital image that can be used as the basis for creating an engraved reproduction of the digital image. The digital image is then converted  604  to a high contract two color image. A merged image is generated 606 to allow the user to create 608 engraving lines in the merged image, which includes the both the two color image and all of the engraving lines that have been created 608. As each engraving line is created 608, the software controls  610  variations in the lines based on the pre-selected line parameters. If the engraved image is complete 612, the engraved image can be generated 614 in its completed form. If not, additional engraving lines can be created 608 until the user is satisfied with the result. The final engraved image can be stored as data for use with existing engraving machines or printed. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. While various methods, steps and systems of the present invention are described herein, any methods, steps and systems similar or equivalent to those described herein may by used in the practice or testing of the present invention. All references cited herein are incorporated by reference in their entirety and for all purposes. 
     While the foregoing advantages of the present invention are manifested in the illustrated embodiments of the invention, a variety of changes can be made to the configuration, design, implementation and construction of the invention to achieve those advantages. Hence, reference herein to specific details of the process and function of the present invention is by way of example only and not by way of limitation.