Abstract:
Forming a character-based monochromatic image from a digital representation of a color image by (1) forming a character-based representation of the color image in which a plurality of color characters each describe the background and foreground color within a defined area of the color image, (2) providing a plurality of color pattern masks each corresponding to a color in the color image and comprised of a pattern of light and dark dots capable of providing, in the monochromatic image, visual discrimination between areas of different color, (3) transforming the color characters to monochromatic characters by replacing the background and foreground color of each color character with the corresponding pattern of light and dark dots, and (4) displaying the monochromatic characters on a character-based output device (e.g., a CRT display driven by a character-based controller).

Description:
BACKGROUND OF THE INVENTION 
     This application is a continuation in part of my copending U.S. application Ser. No. 595,027, filed Mar. 30, 1984, entitled Monochromatic Representation Of Color Images, hereby incorporated by reference. 
    
    
     1. Field of the Invention 
     The present invention relates to the processing and representation of color images and, more particularly, to a method and apparatus for the representation of color images in data processing systems having monochromatic output devices, such as printers and CRT displays. In this context, an image may be defined as a visual representation of information wherein the information may be pictorial or textual or both and may be comprised of alphanumeric characters or symbols or graphic characters, symbols or elements or a combination thereof. A color image may be further defined as an image wherein the elements or areas comprising the image, whether alphanumeric or graphic, are defined by various colors. 
     2. Prior Art 
     Many presently available data processing systems, ranging from public data base television type systems (such as the TELETEL and PRESTEL videotex systems), to `home` computers, to very expensive and complex computer-aided-design (CAD) systems, are capable of manipulating and representing monochromatic and color images. Many systems, however, are wholly or partially limited to monochromatic imagery, either for cost considerations or because image generation and display is a secondary or later added capability of the system. For example, a system may originally have been designed only for monochromatic operations or, while the system itself is capable of operating with color images, the display or hard copy devices connected for the system, such as the CRT and printers, may have only monochromatic capabilities. A recurring problem with systems having image capabilities is presented whenever color images, for example, generated or provided by a system having color image capabilities, are to be visually represented by a system having, for example, only a monochromatic CRT or monochromatic printers. The problem arises when the owner of a personal computer with a conventional 80 column by 24 line monochromatic CRT display desires to communicate with a videotex service (e.g., TELETEL and PRESTEL) that transmits information intended to be viewed on a 40 column by 24 row color display. In general, visual outputs of color images by monochromatic means have proven unsatisfactory, the images being esthetically unpleasing or in many cases visually distorted or transformed to an unacceptable extent. 
     One basis of the problem is that monochromatic and color processes differ in the information presented to a viewer in order for the viewer to distinguish between areas of an image. That is, color processes distinguish between various areas of an image by both color and shade of color, that is, the lightness or darkness of a color. For example, three areas may be distinguished in that one is red, one is light blue and one is dark blue; the red area is distinguished from the blue areas by color and the blue areas are distinguished by being of differing shades of blue. In monochromatic processes, however, the various areas of an image are distinguished only by shade, generally referred to as `half tones`, ranging from `black` to `white`. 
     A transformation of a color image to a monochromatic image thereby requires that color and shade information contained in a color image be transformed into shade information in a monochromatic image. This results, in present systems, in a loss or distortion of visual information. For example, in the simplest systems the `dark` combinations of color and shade information from a color image are transformed into a `black` monochromatic shade while the `light` combinations are transformed into a `white` monochromatic shade. The result can be a total distortion of the original color image and at least a loss of visual information and a degradation of visual esthetics. 
     In more complex systems, the various combinations of color and shade appearing in the color image original are transformed into their nearest equivalent `gray scale` monochromatic shade. The most common example of such a system is in `black and white` photography of a colored object, such as a landscape; that is, the various colors and shades appearing in the scene are replaced, in the photograph, by their shade of gray equivalents. While such a system provides less distortion than the simple system described above, there may still be some distortion of the original visual information and often a loss of esthetics. This distortion occurs because many combinations of color and shade have the same `gray scale` equivalent; for example, a red area, a blue area and a green area, easily distinguishable in color, may have the same gray equivalent and appear as the same shade of gray in the monochromatic image. 
     It is thereby an object of the present invention to provide an improved method and apparatus for representing color images through monochromatic means. 
     SUMMARY OF THE INVENTION 
     In general the invention features forming a character-based monochromatic image from a digital representation of a color image by (1) forming a character-based representation of the color image in which a plurality of color characters each describe the background and foreground color within a defined area of the color image, (2) providing a plurality of color pattern masks each corresponding to a color in the color image and comprised of a pattern of light and dark dots capable of providing, in the monochromatic image, visual discrimination between areas of different color, (3) transforming the color characters to monochromatic characters by replacing the background and foreground colors of each color character with the corresponding pattern of light and dark dots, and (4) displaying the monochromatic characters on a character-based output device (e.g., a CRT display driven by a character-based controller). 
     In preferred embodiments, each monochromatic character comprises a matrix of pixels and each matrix of pixels is represented in a memory as a corresponding matrix of bits; a color-pattern matrix of bits is provided to represent each color pattern mask, with a bit in one state representing a light dot or a portion thereof and a bit in the other state a dark dot or a portion thereof; there is generated for each color character a foreground-background matrix of bits in which a bit in one state represents the presence of foreground color and a bit in the other state the presence of background color, the foreground-background matrix is combined with the color-pattern matrix of the foreground color in such a manner as to replace the bits in the foreground-background matrix with the bits in the color-pattern matrix in areas of foreground color, and the foreground-background matrix is combined with the color-pattern matrix of the background color in such a manner as to replace the bits in the foreground-background matrix with the bits in the color-pattern matrix in areas of background color; color characters are fewer in number than monochromatic characters and the defined area represented by each color character is larger than the area of the monochromatic image represented by the monochromatic character; the color characters include alphanumeric characters having the foreground color in the body of the character and the background color elsewhere and the transforming step includes the steps of generating for each color character at least two monochromatic characters one of which is a space character (all background), so that the body of the character appears in fewer than all of the monochromatic characters corresponding to the color character; there are two monochromatic characters for each color character and one of the two monochromatic characters is made a space character (all background) and the other contains the body of the alphanumeric character; there are two monochromatic characters for each color character and the color characters include graphical characters of a type having two vertical rows of blocks each of which can be foreground or background color and wherein a first monochromatic character containing one vertical row of blocks is formed and a second monochromatic character containing the other vertical row of blocks is also formed; the color image comprises a videotext image; the character-based output device is capable of displaying no more than a maximum number of monochromatic characters at any one time and wherein a newly generated monochromatic character is compared to a library of earlier generated monochromatic characters already part of the monochromatic image and is added to the library only if the newly generated character is not already present there; the library is a dedicated character memory in circuitry controlling said output device; redundancies (e.g., presence of spaces in portions of enlarged alphanumeric characters) in the monochromatic characters are detected and only one character is added to the library instead of one for each redundant character; fewer color pattern masks are provided than there are colors in the color image and each color for which no pattern mask is provided is represented as the inverse of one of the patterns by instructing the output device to display a character containing that color in a reverse video manner; color characters containing both a color for which there is a color pattern and colors for which an inverse of a pattern is required are transformed into monochromatic characters by doing the inversion of color pattern during the process of substituting the color patterns for the foreground and background areas of a character. 
     In another aspect of the invention, the color pattern masks used are those given in the tables in the text of the specification. 
     Other features and advantages of the invention will be apparent from the following description of preferred embodiments and from the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of a computer system incorporating the present invention; 
     FIGS. 2A and 2B are a block diagram of the computer system of FIG. 1; 
     FIG. 3 is a diagrammic representation of the software structure of the computer system of FIGS. 1, 2A and 2B; 
     FIGS. 4A and 4B are a representation of 8 by 8 color pattern masks for the colors black, red, green, yellow, blue, magenta, cyan and white; 
     FIGS. 5A, 5B and 5C are a representation of 20 by 16 color pattern masks for the colors black, red, green, yellow, blue, magenta, cyan and white; 
     FIG. 6 is a diagrammatic illustration of the color to monochromatic image transformation method of the present invention. 
     FIG. 7 is a diagrammatic illustration of the character enhancement method of the present invention; and 
     FIGS. 8A, 8B and 8C are illustrative representations of a color image transformed into a monochromatic image with, respectively, 8 by 8 arrays, 20 by 16 arrays and with enhancement of alphanumeric characters. 
     FIGS. 9A, 9B and 9C are illustrations of typical videotext graphical and alphanumeric characters. 
     FIGS. 10 and 11 show the enlargement that the graphical and alphanumeric videotext characters undergo for display on an 80-column CRT. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The following description will first briefly present the general structure and operation of the hardware and software of a computer system incorporating the present invention and capable of performing image processing and display operations and of communications operations, including communications of images. The structure and operation of such a system will be well understood, as presented herein, by one of ordinary skill in the art and further details of the structure and operation of such a system are presented in U.S. patent application Ser. No. 440,668, filed Nov. 10, 1982 and incorporated herein by reference. The specific system selected for illustrative purposes is a Wang &#34;Professional Computer&#34; available from Wang Laboratories, Inc., Lowell, MA 01851. Having presented a context, that is, apparatus in which to practice the invention, the color to monochromatic image transformation method of the present invention will then be described in detail. 
     The following will then describe an exemplary color image system which may be used as source of color images to be transformed by the above described data processing system. The color images and system described therein are representative of many other commonly used color image systems which may be sources of color images to a system as described above. Other sources of color images, such as color graphic computer systems, may also serve as sources of color images, as may the exemplary system described in the present patent application. In the latter case, the color transformation of the present system may be used, for example, to transform a color image generated by a system when a monochromatic printer connected from the source system is used to provide a hard copy of images created therein. 
     The color transformation of the present invention may be used in relation to videotex systems such as TELETEL and PRESTEL. PRESTEL is a public data base television type system used in the United Kingdom; PRESTEL is a trademark of the British Post Office for PRESTEL services. PRESTEL is presently used, for example, to selectively distribute, under viewer control, information of interest to the public from a central PRESTEL data base. The information contained in this data base may pertain, for example, to weather and stock market reports and shopping guides and entertainment guides. The information so provided is primarily in the form of color images containing both text, that is, alphanumeric characters and symbols, and graphic or pictorial elements. 
     1. COMPUTER SYSTEM STRUCTURE AND OPERATION 
     Referring to FIG. 1, an isometric view of the computer system is shown. System 10 includes a Display 12, a Keyboard 14 and a Central Processing Unit (CPU) 16. Display 12 and Keyboard 14 are the primary means by which information, for example, text, is communicated between the system and a user. CPU 16, which is connected to Display 12 and Keyboard 14 by cables which are not shown, includes a memory for storing programs and data and a general purpose arithmetic and logic unit (ALU). CPU 16 may further include disc drives for storing programs and data and interfaces to peripheral devices, such as printers, disc drives and telecommunications devices. As described above, System 10 may be comprised, for example, of a &#34;Professional Computer&#34; available from Wang Laboratories, Inc., Lowell, MA 01851. 
     A. Hardware Structure and Operation 
     a. ALU and Busses 
     Referring to FIGS. 2A and 2B, a block diagram of System 10 is shown. System 10&#39;s ALU in CPU 16 is comprised of a Main Processor (Main P) 18 and a Co-Processor (CO-P) 20. Main P 18 and CO-P 20, may, for example, respectively be a 16 bit Intel 8086 ALU and an Intel 8087 numerics processor extension. Main P 18 and CO-P 20 perform all arithmetic and logic operations for CPU 16, including addressing, memory references, and control of Input/Output (I/O) operations. 
     Main P 18 and CO-P 20 communicate through Local Bus 22 and with the remainder of CPU 16, Display 12, Keyboard 14 and all peripheral devices through Address Bus 24, Data Bus 26 and Control Bus 28. The interface between Main P 18 and CO-P 20 and Busses 24, 26 and 28 is through Address Latch 30, Data Transceiver 32 and Bus Control 34. 
     b. Internal Control Logic 
     Referring next to CPU 16&#39;s internal control logic, associated with Main Pbeing provided with three spaced apart upstanding spacers 32. 
     In more detail, it will be seen that rear sidewall 12 is integrally joined with each of the sidewalls 16, 18, at smooth, rounded rear corners 34. Moreover, the wall 12 is provided with a total of five formed recesses 36 therein, respectively located directly beneath an associated connector wall 26 in the region between the tube-receiving regions 24. 
     Attention is next directed to FIGS. 1 and 3 which depict the particular construction of front wall 14. In this regard, it will be seen that the front wall 14 is integrally connected with the sidewalls 16, 18 at smooth, rounded corners 38. Moreover, the front wall 14 includes a series of openings 40 therein respectively in communication and alignment with the corresponding tube-receiving regions 24. It will be noted that four openings 40 of relatively deep configurations are provided, along with two openings 40a of somewhat shallower configuration. The openings 40, 40a are designed to receive and accommodate the connector prongs of fluorescent tubes received within the supports, as those skilled in the art will readily appreciate. However, it will be observed that each of the recesses 40, 40a, at the left hand margin thereof as viewed in FIGS. 1 and 2, includes a somewhat triangularly-shaped ledge or platform 42 and a correspondingly shaped relieved zone. As explained previously, other embodiments of the support provide a different placement for the platforms 42 and relieved zones. In particular, in another embodiment of the invention, the platforms 42 and relieved zones are provided at the righthand margin of each recess 40, 40a, as opposed to the configuration specifically depicted in FIG. 1. Thus, and considering an interfitted stack of the tube supports, the left and righthand placement of platforms 42 would alternate in the stack so as to establish and maintain a proper spacing between individual interfitted supports. 
     Referring particularly to FIGS. 2 and 3, it will further be seen that front wall 14 is provided with a total of five somewhat triangularly shaped, arcuate in cross section, open top, upwardly diverging recessed zones 44. These zones are defined by correspondingly shaped indentations in wall 14 as will be readily seen, with such indentations being in opposed relationship to each of the five connector walls 26 (see FIG. 2). As a result of this configuration, it will be perceived that each of the connector walls 26, at the region of front wall 14, is somewhat Y-shaped in configuration, with the base of the Y extending from the corresponding notch 28, and with the bifurcated portion thereof surrounding and defining the upper end of each zone 44. As readily observable from FIGS. 1 and 2, front wall 14 presents an effective thickness attributable to the noted Y-shaped sections together with the bottom walls 46 and 46a of the respective openings 40 and 40a. In addition, the overall front wall 14 presents an upright inner surface in the form of respective arcuate walls 48 joined to the Y-shaped sections and opening-defining walls and extending downwardly therefrom for joinder with the concavo-convex walls 22. The arcuate walls 48 in turn define an upright abutment surface for the end of a fluorescent tube situated within each corresponding region 24. 
     Rear side lip 20 is provided with a plurality, here seven, of upstanding spacer nibs 50. As illustrated, the nibs 50, in the depicted embodiment, are located at the ends of the lip 20, and just to the left of each recess 36. The purpose of these nibs 50 will be made clear hereinafter. 
     Each of the concavo-convex wall sections 22 include a stepped, arcuate, end cap-receiving wall portion 52 which extends rearwardly from each associated wall 48 and terminates at the frontmost end of the associated notches 28 as shown. The wall portion 52 as indicated receive the metallic end caps provided on the fluorescent tubes. 
     The remainder of the concavo-convex wall sections extending rearwardly from the portions 52 to rear wall 12 are in the form of alternating downwardly and upwardly opening, vertically spaced apart arcuate tube-engaging wall sections 54, 56. That is to say, the majority of the length of each concavo-convex wall section 22 includes a plurality of axially spaced apart, arcuate, upwardly opening and diverging wall sections 56 presenting a radius of curvature conforming to that of the sidewall of a fluorescent tube. These spaced apart wall sections 56, at their respective side margins, merge into and form a part of similarly curved main sidewall portions 58 which extend upwardly and are integral with the upper connector walls 26. 
     The concavo-convex walls 22 further include a second plurality of downwardly opening and diverging wall portions 54 which similarly have a radius of curvature conforming to the sidewall of a fluorescent tube. The respective marginal ends of each wall section 54 are joined with upwardly extending walls 60 (see FIG. 8) which extend upwardly to merge into main wall portion 58. The alternating walls sections 54, 56 are joined together by means of vertical walls 62 in order to maintain the wall sections in vertically spaced relationship to one another. As best seen in FIG. 8, each upwardly opening wall section 56 is spaced above the adjacent wall section 54. Indeed, the lateral side margins of the wall sections 54 extend slightly below the bottom edge of the sidewalls 16, 18, and rear wall 14. 
     Each of the wall sections 54, 56 is provided with a plurality of relatively small cushioning striations or ribs 64 formed therein during the vacuum forming process of the dunnage support 10. In like manner, each end cap-receiving wall portion 52 is similarly striated. Hence the wall sections 54, 56 each present an undulating, tube-engaging surface. 
     The element 10 is formed in a female mold so that the thickness of each of the upper connector walls 26, 30 is greater than that of the lower downwardly opening wall sections 54. Indeed, the thickness of the endmost portions of the wall sections 54 are on the order of 0.004 inch, and are effectively transluscent. On the other hand, the connector walls 26, 30 are virtually the same thickness as the starting sheet material, or preferably about 0.014 inch. 
     Attention is next directed to FIG. 9 which depicts a vertical stack 66 of interfitted dunnage supports in accordance with the invention. This stack is made up of two particular embodiments of the dunnage supports, namely the supports 10 fully described above, together with alternating supports 10a. The supports 10a are in all respects identical with the supports 10, save for the fact that in the supports 10a, the nibs 50a thereof are laterally offset from the nibs 50 of the supports 10, and the ledges or platforms thereof (not shown) are laterally offset from the platforms 42. As a consequence of this construction, it will be seen that the nibs 50, 50a alternate in a stairstep fashion throughout the stack 66; furthermore, the spacing platforms of the supports 10, 10a similarly alternate in a stair-step fashion. By virtue of this configuration, each of the nibs 50, 50a contacts the planar underside of the lip of the support next above in the stack; likewise, each individual set of ledges or platforms engages the full heighth wall of the Y-shaped section of the next adjacent support. The heighth of the nibs and the vertical recess of the platforms are correlated so as to maintain an even spacing between individual supports about the entire periphery thereof. This prevents full nesting of the respective supports 10, 10a and effectively presents a series of substantially even, elongated spaces 68 between individual dunnage supports in the stack 66. As a consequence, the stack 66 can be placed in automatic dispensing equipment, and the spaces 68 afford adequate clearance for the insertion of dispensing equipment between individual supports in the stack. Thus, such dispensing equipment can be used to good effect to achieve easy, high speed automated dispensing of the individual supports. 
     Although PVC having a thickness of 0.014 inch is the preferred sheet material for use in forming the supports of the invention, other current or future equivalent materials may also be used. For example, it is believed that thermoplastic polyester or polyethylene terephthalate synthetic resins can also be used to good effect in the invention, with the thicknesses of these materials being substantially the same as outlined above. In order to provide the most advantageous protection for the fluorescent tubes, it is preferred to employ synthetic resin materials having a durometer value (Shore D per ASTM D-2240) of from about 80 to 90 (most preferably 84), and a modulus of elasticity of from about 400,000 to 440,000, ASTM D-790 (most preferably 420,000). The most preferred PVC material further has a specific gravity 1.35, ASTM D-792; a tensile strength of 6750 psi, ASTM D-638; a tensile modulus of 315,000 psi, ASTM D-638; a flexural modulus of 420,000 psi, ASTM D-790; and a deflection temperature at 264 psi of 58° C., ASTM D-648. 
     In addition, the various structural features of the dunnage supports assures that a package of fluorescent tubes with individual supports between respective layers thereof can withstand potentially destructive impact forces. That is to say, a given package containing four layers of tubes would make use of five dunnage supports at each end of the tubes, with four of the supports receiving the tubes as illustrated in FIG. 8, and with one support being inverted. In any event, actual testing with the dunnage elements hereof has proved that they are fully capable of supporting and protecting fluorescent tubes in a manner at least equivalent to conventional pulp dunnage supports. Such protection is believed to stem from the inherent flexibility of the synthetic resin material, and also by virtue of the striations 64 provided on the tube-engaging surfaces. Furthermore, the various recesses such as the notches 28 and zones 44, afford a controlled collapse to the dunnage elements which has been found to safely absorb potentially destructive forces. 
     In addition to the foregoing, it has been found that it is advantageous to provide a spacing between the longitudinal axes of adjacent pairs of tube-receiving regions 24 slightly differently than the spacing between other pairs of axes. This slight differential is in itself believed to enhance the protective function during an impact situation. To further enhance the protective function, the shape, spacing, contours, dimensions and ribbed texture of the areas 54, 56, 58, 60 and 62 are individually shaped to be slightly different from one another. 
     Finally, it will also be noted that the central connector wall 26 is slightly wider than the remaining connector walls on either side thereof. This not only enhances the strength of the central section of the support, but also facilitates automated insertion of thin vertical corrugated material between the central tubes during the packing process. 
     As indicated above, a prime feature of the present invention resides in the provision of dunnage supports designed to only incompletely nest in a stack thereof so as to present uniform spacings between pairs of elements and thus facilitate machine dispensing thereof. While in the preferred form of the invention use in made of an alternating nib and ledge arrangement respectively located along the rear and front side edges of the supports, the invention is not so limited. Thus, it will be appreciated that there are a multitude of ways to form spacing elements in the supports themselves in such a manner as to insure the partial nesting feature described above. All such equivalents are therefore deemed to be within the spirit and scope of the present invention.