Abstract:
A computer-implemented method alters component colors of art work associated with a drawing stroke on an electronic document. In one aspect, the invention generates a darkness value for each component color of each original color; generates a new color to substitute for each original color, the component color values of the new color being generated according to the corresponding darkness value and a reference color; and alters the component colors of the art work based on the new color values. In a second aspect, the invention provides a computer-implemented method for altering a component color of art work by mapping the component color to a new color based on a color space associated with the component color and applying the resulting color to components of the art work. In a third aspect, the computer-implemented method for altering component colors of the art work includes converting the color of components into a hue, saturations and brightness (HSB) color space; biasing hue values of a key color, a paint color, and a stroke color; mapping the hue values; transforming saturation and brightness values; unbiasing the hue values; converting the resulting color into original color space of the stroke color; and applying the resulting color to components of art work stroke derived from the components of the base art work.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to altering component colors of art work associated with a drawing stroke on an electronic document. 
     In modern drawing programs such as Adobe Illustrator®, produced by Adobe Systems Incorporated of San Jose, Calif., graphical patterns are made available to a user to enhance the aesthetics of a document. In these programs, the user is able to select a graphical pattern for a drawing the user is creating, and then manually place individual copies of the selected graphical pattern wherever desired on the drawing being created. For example, the user may desire to place a border around a drawing. The creation of the border would require the user to select a graphical pattern and then individually place multiple copies of the pattern around the periphery of the drawing. To save the user time in individually placing the graphical patterns so as to form the border or other shape, certain programs support a process known as tiling for placing graphical patterns or other shapes such that graphically pleasing borders can be produced. As discussed in U.S. application Ser. No. 08/580,472, filed on Dec. 28, 1995, and entitled “AUTOMATIC GRAPHICAL PATTERN PLACEMENT”, hereby incorporated by reference, a path on an electronic document is sketched by the user and a graphical pattern is selected before the graphical pattern is automatically placed along the path by a programmed computer such that the graphical pattern follows the orientation and curvature of the path. In this manner, graphically pleasing borders or shapes can be produced with only a minimal amount of user time. 
     Certain programs support additional enhancements on the border generation process such as changing a stroke color associated with the shape of the border. Other extensions support complex strokes which, instead of being a line, may be an art work which has been distorted to follow an outline of the shape, or a tile which has been replicated along the outline of the shape. The complex strokes are often referred to as “art work strokes”, while the art work that has been distorted along the shape or that composes the tile that has been replicated along the shape is called a “base art work” of the stroke. 
     SUMMARY OF THE INVENTION 
     The present invention provides a computer-implemented method for altering component colors of art work associated with an art work stroke on an electronic document. In one aspect, the invention generates a darkness value for each component color of each original color; generates a new color to substitute for each original color, the component color values of the new color being generated according to the corresponding darkness value and a reference color; and alters the component colors of the art work based on the new color values. 
     Implementations of the invention include the following. The color generating step includes determining whether the darkness is below a predetermined threshold and if so, selecting a new color between a white value and a stroke color value. The color generating step also includes determining whether the darkness value is equal to a predetermined threshold, and if so, setting a new color to a stroke color. Moreover, the color generating step further includes determining whether the darkness value exceeds a predetermined threshold, and if so, selecting a new color between a stroke color value and a black value. Particularly, where a white color value is equal to zero and a black color value is equal to 1, the selection of the new color includes comparing the darkness value to 0.5. 
     In another aspect, the invention provides a computer-implemented method for altering a component color of art work by converting the color of components and a key color into a color space of a stroke color; transforming the color of the components based upon the absolute and relative differences among the key color, the component color, and a stroke color; and applying the resulting color to components of an art work stroke derived from the component of the base art work. Implementations of the second aspect may include determining whether a stroke color belongs to a red green blue (RGB) color space or to a cyan magenta yellow black (CMYK) color space and performing the appropriate conversions to the color space. 
     In a third aspect, a computer-implemented method for altering component colors of art work includes converting the color of components into a hue, saturations and brightness (HSB) color space; biasing hue values of a key color, a paint color, and a stroke color; transforming saturation and brightness values; mapping the hue values of the key color, the paint color, and the stroke color; unbiasing the hue values; converting the resulting color into original color space of the stroke color; and applying the resulting color to components of art work stroke derived from the component of the base art work. Implementations of the invention include taking an input hue value and linearly interpolating the hue value. 
     Advantages of the invention include the following. When the user creates a shape with an art work stroke and then sets the stroke color of the shape, the output is intuitive. Thus, a system requiring a minimal amount of user control and interaction is needed for applying the stroke color associated with the shape to the art work stroke. Moreover, the system needs to maintain a variation in color and preserve the integrity of the art work. 
     Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawings are provided to the Patent and Trademark Office with payment of the necessary fee. The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
     FIG. 1 is a block diagram of an exemplary computer system for automatically placing graphical patterns in accordance with the invention. 
     FIG. 2 is a flow chart of a first process for altering component colors of an art work in accordance with the invention. 
     FIG. 3 is a flow chart of a second process for altering component colors in accordance with the invention. 
     FIG. 4 is a flow chart of a third process for altering component colors in accordance with the invention. 
     FIGS. 5,  6  and  7  are examples illustrating the operation of the first, second and third color altering processes of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a block diagram of an exemplary computer system  10  for automatically altering component colors of tiles in accordance with the invention. The computer system  10  includes a digital computer  11  and may include a display screen (or monitor)  22 , a printer  24 , a floppy disk drive  26 , a hard disk drive  28 , a network interface  30 , a keyboard  34 , and a mouse (pointing device)  35 . The digital computer  11  includes a microprocessor  12 , a memory bus  14  and a random access memory (RAM)  16 , and may include a read only memory (ROM)  18 , a peripheral bus  20 , and a keyboard controller  32 . The digital computer  11  can be a personal computer (such as an IBM compatible personal computer), a workstation computer (such as a Sun or Hewlett-Packard workstation), or some other type of computer. 
     The microprocessor  12  is a general purpose digital processor which controls the operation of the computer system  10 . The microprocessor  12  can be a single-chip processor or can be implemented with multiple components. Using instructions retrieved from memory, the microprocessor  12  controls the reception and manipulation of input data and the output and display of data on output devices. In particular, the microprocessor  12  can be programmed to automatically place graphical patterns along a path within an electronic document. 
     The memory bus  14  is used by the microprocessor  12  to access the RAM  16  and the ROM  18 . The RAM  16  is used by the microprocessor  12  as a general storage area and as scratch-pad memory, and can also be used to store input data and processed data. For example, input data from a file of a drawing or other electronic document can be in the form of Adobe Illustrator® program file format, Portable Document Format (PDF), or the like. If the input data also contains text regions, PostScript® or other page description language character codes may be used to represent the characters. The ROM  18  can be used to store instructions for execution by the microprocessor  12  as well as image descriptions used to display images in a specific format. 
     The peripheral bus  20  is used to access the input, output, and storage devices used by the digital computer  11 . These devices may include the display screen  22 , the printer device  24 , the floppy disk drive  26 , the hard disk drive  28 , and the network interface  30 . The keyboard controller  32  may be used to receive input from keyboard  34  and send decoded symbols for each pressed key to the microprocessor  12  over bus  33 . 
     Referring now to FIG. 2, a process  100  for altering component colors of art work associated with a tile is shown. Generally, colors in a color model specification are given in a particular color space. Color spaces are defined by sets of color components that can be combined to create any color in the color space&#39;s gamut. For example, red green blue (RGB) is a color space, so is the set of colors cyan magenta yellow and black (CMYK). In addition to these device-dependent color spaces there are device independent color spaces such as CIE L*a*b* in which colors are specified according to an international standard rather than percentages of phosphor intensity (RGB) or ink (CMYK) which are inherently device-dependent. 
     For each component color of the art work stroke, the process  100  initially generates a darkness value (step  102  ) and a new color is generated based on the darkness value. Thus, if the darkness value is less than a predetermined threshold, such as a midpoint between a black value (which may be represented as 1) and a white value (which may be represented as 0) (step  104 ), the process  100  generates a new color which varies between the stroke color and the white value (step  106 ). Alternatively, in the event that the darkness value equals the threshold value (step  108 ), the process  100  sets the new color to the stroke color (step  110 ). Alternatively, in the event that the darkness value exceeds the threshold (step  112 ), the process  100  generates a new color which varies between the stroke color and the black value (step  114 ). From step  106 ,  110 ,  112  or  114 , the process  100  exits (step  116 ). A pseudo code for process  100  is shown in the table below: 
     For each component of the base art work: 
     darkness: Computed darkness of the component&#39;s color 
     The method used to compute the darkness depends upon the color 
     management system installed on the system. The result is 
     normalized so that 0 represents white, 1 represents black, and 
     values between 0 and 1 represents values in between. 
     stroke: Stroke color 
     result: New color 
     If darkness=0.5 
     The new color is the same as the stroke color 
     result=stroke 
     If darkness &lt;0.5 
     The new color is a lighter version of the stroke color, uniformly 
     varying between the stroke color at darkness 0.5 and white at 
     darkness 0 
     If stroke color is in the RGB color space: 
     result.red=1 −(darkness/0.5) * (1−stroke.red); 
     result.green=1 −(darkness/0.5) * (1−stroke.green); 
     result.blue=1 −(darkness/0.5) * (1−stroke.blue); 
     If stroke color is in the CMYK color space: 
     result.cyan =(darkness/0.5)* stroke.cyan; 
     result.magenta=(darkness/0.5)* stroke.magenta; 
     result.yellow =(darkness/0.5)* stroke.magenta; 
     result.black =(darkness/0.5) * stroke.black 
     If darkness&gt;0.5 
     The new color is a darker version of the stroke color, uniformly 
     varying between the stroke color at darkness 0.5 and black at 
     darkness 1 
     If stroke color is in the RGB color space: 
     result.red=stroke.red*(1−((darkness−0.5)/0.5)); 
     result.green=stroke.green*(1−((darkness−0.5)/0.5)); 
     result.blue=stroke.blue*(1−((darkness−0.5)/0.5)); 
     If stroke color is in the CMYK color space: 
     result.cyan=stroke.cyan; 
     result.magenta=stroke.magenta; 
     result.yellow=stroke.yellow; 
     result.black=stroke.black+((darkness−0.5)/0.5)* (1−stroke.black); 
     Apply result color to components of the art work stroke that were derived from this component of the base art. 
     Referring now to FIG. 3, a second process  120  for altering component colors of art work associated with the art work stroke is shown. For each component color of the art work stroke, the process  120  initially tests whether the stroke color is in a red green blue (RGB) color space (step  122 ). If so, the process  120  converts the component colors to the RGB color space and maps each of them to a new color in the RGB color space. 
     Alternatively, in the event that the stroke color is not in the RGB color space, the process  120  further checks whether the stroke color is in a cyan magenta yellow or black (CMYK) color space (step  126 ). From step  126 , if the stroke color is not in the CMYK color space, the process exits (step  132 ). Otherwise, the process  120  converts the component colors to the CMYK color space and maps each of them to a new color in the CMYK color space (step  128 ). From step  124  or step  128 , the process  120  applies the result color to the art work stroke component (step  130 ) before exiting (step  132 ). 
     The processes  120  and  140  transform colors based on a key color, which is a color value that is present in the base art for the artwork stroke. The key color is the color that will become the stroke color in the final result. All components that are the key color become the stroke color. All components that are not the key color adopt a new color, and the processes  120  and  140  give two different ways to pick this new color. For example, in the process  120 , if a component is somewhat more red than the key color, the chosen color is a color that is somewhat more red than the stroke color. A pseudo code for the process  120  is shown in the following table: 
     Convert key color into color space of stroke color if it is not there already. 
     For each component of the base art: 
     Convert color of component into color space of stroke color if it is not there already. 
     key: Key color 
     paint: Component color 
     stroke: Stroke color 
     result: New color 
     If stroke color is in the RGB color space: 
     result.red=Map(paint.red, key.red, stroke.red); 
     result.green=Map(paint.green, key.green, stroke.green); 
     result.blue=Map(paint.blue, key.blue, stroke.blue); 
     If stroke color is in the CMYK color space: 
     result.cyan=Map(paint.cyan, key.cyan, stroke.cyan); 
     result.magenta=Map(paint.magenta, key.magenta, stroke.magenta); 
     result.yellow=Map(paint.yellow, key.yellow, stroke.yellow); 
     result.black=Map(paint.black, key.black, stroke.black); 
     Apply result color to components of the art work stroke that were derived from this component of the base art. 
     The Map function is shown in the following table: 
     float Map(float paint, float key, float stroke) { 
     float result; 
     if (paint&lt;key) { 
     if (stroke&lt;key) 
     result =paint * stroke /key; 
     else 
     result =paint +stroke −key; 
     } else if (paint&gt;key) { 
     if (stroke&gt;key) 
     result=stroke+(paint −key)/(1 −key)*(1−stroke); 
     else 
     result=paint+stroke−key; 
     } else result=stroke; 
     return result; 
     } 
     If the Map function may use a relative mapping or an absolute mapping, depending on which method results in at a smaller change. For example, if the key value is 0.4 and the paint value is 0.2, the relative relationship between the key and the paint values is 50% (the paint is 50% of the key) and the absolute relationship is −0.2 (the paint value is 0.2 less than the key value). If the stroke value is 0.6, the relative mapping would be 0.3 (50% of 0.6) and the absolute mapping would be 0.4 (0.6 −0.2). Since the absolute mapping gives a smaller change, it is used, and the result is 0.4. If the stroke is 0.3, the relative mapping would be to 0.15 (50% of 0.3) and the absolute mapping would be to 0.1 (0.3−0.2). Since the relative mapping gives a smaller change, it is used, and the result is 0.15. Hence, the result is that the mapping always produces colors that are close to the stroke color. 
     To further illustrate the mapping process, assume a piece of art work has 6 colors: 0% red, 10% red, 20% red, 60% red, 80% red, and 100% red. The colors are mapped so that 20% red becomes 60% red. If the mapping is done using absolute differences, the result is 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Original 
                 New 
                 Comment 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 0% 
                 40% 
                 20 less than the key color 
               
               
                   
                 10% 
                 50% 
                 10 less than the key color 
               
               
                   
                 20% 
                 60% 
                 the key color 
               
               
                   
                 60% 
                 100% 
                 40 more than the key color 
               
               
                   
                 80% 
                 100% 
                 should be 120%, but 100% is the max 
               
               
                   
                 100% 
                 100% 
                 should be 140%, but 100% is the max 
               
               
                   
                   
               
             
          
         
       
     
     A shortcoming of the absolute difference method is that many of the color differences in the original have been eliminated because of the clipping that occurs at 100%. The result may not resemble the original because of this. In contrast, if the mapping is done using relative differences, the result is 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Original 
                 New 
                 Comment 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 0% 
                 0% 
                 0 stays 0 in a relative mapping 
               
               
                   
                 10% 
                 30% 
                 ½ of the key color 
               
               
                   
                 20% 
                 60% 
                 the key color 
               
               
                   
                 60% 
                 80% 
                 halfway from the key color to 100% 
               
               
                   
                 80% 
                 90% 
                 ¾ of the way from the key color to 100% 
               
               
                   
                 100% 
                 100% 
                 100 stays 100 in a relative mapping 
               
               
                   
                   
               
             
          
         
       
     
     However, a shortcoming of the relative difference approach is that a relatively small color variation in the original among the first 3 colors (0%, 10%, 20%) becomes a very large color variation in the result (0%, 30%, 60%). In comparison, if the mapping is done with the process  120  using a minimum of the relative and absolute differences, the result is: 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Original 
                 New 
                 Comment 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 0% 
                 40% 
                 20 less than the key color 
               
               
                   
                 10% 
                 50% 
                 10 less than the key color 
               
               
                   
                 20% 
                 60% 
                 the key color 
               
               
                   
                 60% 
                 80% 
                 halfway from the key color to 100% 
               
               
                   
                 80% 
                 90% 
                 ¾ of the way from the key color to 100% 
               
               
                   
                 100% 
                 100% 
                 100 stays 100 in a relative mapping 
               
               
                   
                   
               
             
          
         
       
     
     The result lacks the aforementioned shortcomings. No clipping occurs, and no small changes turn into large changes. 
     Turning now to FIG. 4, a third process for altering component colors of art work associated with the art work stroke is illustrated. In this process, if a component&#39;s color has a hue that has a particular relationship to the hue of the key, the chosen color is a color that has a similar relationship to the hue of the stroke color. 
     For each component color of the art work stroke, the process  140  initially converts the color into a hue, saturation and brightness (HSB) color space (step  142 ). The hue component of HSB space is highly nonlinear to the human vision system. The colors of the spectrum appear approximately in the following order: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 0 
                 red 
               
               
                 0.08 
                 orange 
               
               
                 0.16 
                 yellow 
               
               
                 0.33 
                 green 
               
               
                 0.50 
                 cyan 
               
               
                 0.66 
                 blue 
               
               
                 0.83 
                 magenta 
               
               
                 1 
                 red (full circle) 
               
               
                   
               
             
          
         
       
     
     The red to yellow section changes much more rapidly than the green-blue section. Additionally, there are wide stretches in the green and blue areas with no visible color change. To compensate for this uneven rate of change, the process  140  biases the hue values of the key color, component color and the stroke color (step  144 ). The process  140  then maps the biased hue values (step  145 ). Next, the process shifts the hue values by adding a component hue to a target hue and subtracting a key hue. Next, the process  140  maps saturation values (step  146 ). Finally, the brightness values are mapped (step  148 ). Next, the process  140  unbiases the hue value (step  150 ). The result is then converted into the original color space of the stroke color (step  152 ). Finally, the process  140  applies the result color to individual components of the art work stroke derived from the component of the base art work (step  154 ) before exiting (step  156 ). A pseudo code for process  140  is shown in the following table: 
     Convert key color and stroke color into HSB color space. 
     For each component of the base art: 
     key: Key color 
     paint: Component color 
     stroke: Stroke color 
     result: New color 
     Convert color of component into HSB color space. 
     Bias hue values of key, paint and stroke colors. 
     result.hue=paint.hue+stroke.hue−key.hue; 
     result.saturation=Map(paint.saturation, key.saturation, stroke.saturation); 
     result.brightness=Map(paint.brightness, key.brightness, stroke.brightness); 
     Unbias hue value of result. 
     Convert result into original color space of stroke color. 
     Apply result color to components of the art work stroke that were derived from this component of the base art. 
     To bias the hue space, take the input hue value (between 0 and 1) and linearly interpolate in the following table shown below for reference: 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Hue 
                 Biased hue 
                 Color 
               
               
                   
                   
               
             
             
               
                   
                 0 
                 0 
                 red 
               
               
                   
                 {fraction (1/12)} 
                 0.17 
                 orange 
               
               
                   
                 ⅙ 
                 0.34 
                 yellow 
               
               
                   
                 ⅓ 
                 0.46 
                 green 
               
               
                   
                 ½ 
                 0.6 
                 cyan 
               
               
                   
                 ⅔ 
                 0.76 
                 blue 
               
               
                   
                 ⅚ 
                 0.91 
                 magenta 
               
               
                   
                 1 
                 1 
                 red again 
               
               
                   
                   
               
             
          
         
       
     
     Linear interpolation in this table is one way to bias the hue space. Other ways may be used, including a different table, or a more complex interpolation than a simple linear interpolation may be used. By biasing the hue space, uneven changes are smoothed out. 
     The result of this bias is that changes in the red/orange/yellow area (0-⅙) are stretched out, while changes in other areas are compressed. To unbias the hue space, the interpolation process is performed in reverse. 
     The basic mapping function is that if hue A is mapped to hue B, then hue C becomes hue B+(C−A). A difference between C and A is taken and the difference is applied to hue B. To illustrate, assume a piece of art work has 2 colors, hue 0 (red) and hue 0.08 (orange). These colors are mapped so that red becomes 0.33 (bright green). Without biasing, the orange becomes 0.42 (=0.33+0.08−0), which is a shade of green that is visually almost identical to the 0.33 green. A very visible difference has been almost eliminated. 
     Conversely, assume a piece of art work has 2 colors, 0.22 (a yellow-green) and 0.38 (a bright green). These colors are visually distinct but similar. These colors are mapped so that the yellow-green becomes red (hue 0). Without biasing, the saturated green becomes 0.16 (=0+0.38−0.22), a saturated yellow that visually is nowhere close to red. Two colors that were close together have become very different. 
     In the first example, the result of biasing 0 and 0.08 are 0 and 0.17. 0 is shifted to 0.46 (the result of biasing 0.33), which makes 0.17 become 0.63 (=0.46+0.17−0). The bias is then reversed, which makes 0.46 become 0.33 and 0.63 become (0.53, a light blue color. The visual relationship between red and orange has been preserved, resulting in green and light blue. 
     In the second example, the result of biasing 0.22 and 0.38 are 0.39 and 0.5. 0.39 is shifted to 0 (the result of biasing 0), which makes 0.5 become 0.11 (=0+0.5—0.39). The bias is then reversed, which makes 0 become 0 and 0.11 become 0.05, an orange red. The visual relationship between yellow-green and green has been preserved, resulting in red and orange-red. 
     Referring now to FIG. 5, an example illustrating the operation of processes  100 ,  120  and  140  on an original art work  200  is shown. FIG. 5 shows two sets of examples associated with stroke colors  202  and  210 . The application of processes  100 ,  120  and  140  to the art work  200  using the stroke color  202  results in new art work  204 ,  206  and  208 , respectively. Similarly, the application of the stroke color  210  to the original art work  200  using processes  100 ,  120  and  140  results in derived art work  212 ,  214  and  216 . As shown in FIG. 5, the application of the process  100  to the original art work  200  generates images where all colors are tints and shades of the stroke color. For instance, the derived art work  204  simply contains tints and shades of the stroke color  202 , which is orange, while the derived art work  212  contains tints and shades of the stroke color  210 , which is green. Moreover, in the event that the original art work  200  contained regions where the white color or black color, these regions would remain white or black. Thus, the process  100  results in derived art work which vary only in the tint and not in the hue of the color. 
     The application of the process  120  to the original art work  200  results in the derived art work  206  and  214 , respectively. In generating the derived art work  206  and  214 , the color of the petals in the original art work  200 , in this case yellow, is the key color. In the original art work  200 , the petals are yellow, while the outline and the center of the flower are reddish in color. Upon the application of the process  120  to the original art work  200  using the new stroke color  202 , the color of the petal is changed from yellow to orange in the derived art work  206 . Additionally, the outline as well as the center of the flowers adopt a strong red hue. Similarly, when the process  120  is applied to the original art work  200  using the new stroke color  210  and the yellow color of the petal as the key color, the derived art work  214  has petals that are green in color while the outline of each of the derived flowers is dark in color due to the mixing of the red color to the green color. 
     The application of the process  140  to the original art work  200  results in derived art work  208  and  216 , respectively. In addition to varying the hue, as in the process  120 , the process  140  additionally uses saturation and brightness values. The application of the hue, saturation and brightness values to the stroke color  202  results in red as well as purplish colors in the derived art work  208 . Similarly, the application of the process  140  to the original art work  200  using the stroke work  210  results in the transformations in the color in the center of the flower of an orange color to a yellow color, the petals from a yellow color to a green color, and the outline from a red color to a brown color of the derived art work  216 . 
     An additional illustration of the application of processes  100 ,  120  and  140  to a second original art work  218  is shown in FIG.  6 . The second original art work  218  is a series of leaves that are connected together. In this example, the color of a leaf  219  serves as the key color for processes  120  and  140 . As shown in derived art work  222  and  232 , all components of the derived art work are in tints or shades of the stroke colors  220  or  230 , respectively. Moreover, as shown in a derived art work  224 , leaves that are more yellow in the original art work  218  are still more yellow in derived art work  224  and  234 . Finally, changes in the hue saturation and brightness values from the original art work  218  results in derived art work  226  and  236  that are distinctly different in color from the original art work  218 . 
     Referring now to FIG. 7, yet another example of the operation of processes  100 ,  120  and  140  on a third original art work  238  is shown. In FIG. 7, the key color for processes  120  and  140  is a color of the background of the tie, in this case maroon. Upon the application of the process  100  to the original art work  238  using the stroke color  240  or  250 , derived art work  242  and  252  are generated respectively. These derived art work are colored in tints and shades of the original colors  240  and  250 , respectively. Moreover, the application of the process  120  to the original art work  238  using stroke colors  240  and  250  generate derived art work  244  and  254 , respectively. It is to be noted that the stripes of derived art work  244  and  254  are bluer than that of the background color. Finally, the application of the process  140  to the art work  238  results in derived art work  246  and  256 , respectively. In derived art work  246  and  256 , changes in the hue, saturation and brightness values from the original values in the original art work  238  results in a different effect for each of the derived art work  246  and  256 . 
     The invention may be implemented as a computer program which is tangibly stored in a machine-readable storage media or device readable by a general or special purpose programmable computer. The program configures and controls the operation of the computer when the storage media or device is read by the computer to perform the procedures described herein. The inventive system may also be considered to be embodied in a computer-readable storage medium, configured with a computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner to perform the functions described herein. 
     The present invention has been described in terms of specific embodiments, which are illustrative of the invention and not to be construed as limiting. Other embodiments are within the scope of the following claims.