Method and system for converting images in computer systems

• US 5,914,723 A
• Filed: 12/30/1996
• Issued: 06/22/1999
• Est. Priority Date: 12/30/1996
• Status: Expired due to Term

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Gajewska, Hania
• Primary Examiner(s): Nguyen, Phu K.
• Application Number:
  US08/777,755
• Time in Patent Office: 904 Days
• Field of Search: 345/431, 345/339, 345/340, 345/342, 345/346
• US Class Current: 345/597
• CPC Class Codes: G06T 11/001 Texturing; Colouring; Generation of texture or colour inpainting G06T5/77

Abstract

The present invention provides a method and system in computer systems for converting an original image into another image having fewer colors than the original image. This method and system attempt to preserve the contrast of the original image. As a result, this method and system are particularly well-suited for converting images that are relatively small in size. A computer system in which the present invention operates includes a computer connected to a display device and a secondary storage device. An image converter is stored in the secondary storage device for execution by the computer. In operation, the computer receives an original image to be displayed on the display device. The image converter converts the original image into another image having fewer colors than the original image. Lastly, the computer displays the converted image on the display device. In order to convert the original image, the image converter determines which pixels in the original image are opaque in the converted image. For the pixels that are opaque in the converted image, the image converter determines a gray-scale representation of the pixels. For the same pixels, the image converter then determines a black-and-white representation of the pixels. Next, the image converter determines the color assigned to the black pixels in the converted image and the color assigned to the white pixels in the converted image. Lastly, the image converter specifies the representation of the converted image.

Claims

1. A method executed in a computer system for converting an image, the method comprising the steps of:

receiving an original image to be displayed, the original image including a plurality of pixels, each pixel having a color associated with the pixel;

converting the original image into another image having fewer colors than the original image by;

determining a first gray-scale representation of the pixels in the converted image so that each pixel has a gray-value in the converted image;

determining a second gray-scale representation of the pixels in the converted image so that each pixel is assigned to a gray-level in the converted image, wherein the number of gray-levels in the converted image is equal to the number of colors in the converted image;

determining a color assigned to the pixels in each gray-level in the converted image; and

specifying a representation of the converted image using the determined second gray-scale representation and the determined colors; and

displaying the converted image using the specified representation of the converted image.

2. The method of claim 1,

wherein each pixel in the original image has an opacity associated with the pixel;

wherein the step of converting the original image further includes the step of determining which pixels in the original image are opaque in the converted image;

wherein the step of determining a first gray-scale representation of the pixels in the converted image includes the step of determining a first gray-scale representation of the pixels that are opaque in the converted image; and

wherein the step of determining a second gray-scale representation of the pixels in the converted image includes the step of determining a second gray-scale representation of the pixels that are opaque in the converted image.

3. The method of claim 2, wherein the step of determining which pixels in the original image are opaque in the converted image includes the steps of:

for each pixel in the original image, determining whether the opacity of the pixel in the original image is greater than or equal to an opacity threshold value and, if so, making the pixel opaque in the converted image, otherwise, making the pixel transparent in the converted image.

4. The method of claim 3, wherein the step of converting the original image further includes the steps of:

determining whether the percentage of the opaque pixels in the converted image is less than an opaque pixel threshold percentage and, if so, lowering the opacity threshold value used for making the pixels either opaque or transparent and then repeating the step of determining which pixels in the original image are opaque in the converted image using the lowered opacity threshold value; and

determining whether the percentage of the transparent pixels in the converted image is less than a transparent pixel threshold percentage and, if so, raising the opacity threshold value used for making the pixels either opaque or transparent and then repeating the step of determining which pixels in the original image are opaque in the converted image using the raised opacity threshold value.

5. The method of claim 1, wherein the step of determining a first gray-scale representation of the pixels in the converted image includes the step of:

for each pixel in the converted image, converting a color representation of the pixel in the original image into a first gray-scale representation of the pixel in the converted image.

6. The method of claim 1, wherein the step of determining a second gray-scale representation of the pixels in the converted image includes the step of:

for each pixel in the converted image, converting the first gray-scale representation of the pixel in the converted image into a second gray-scale representation of the pixel in the converted image by determining the gray-level in which the gray-value of the pixel in the converted image falls and assigning the pixel to the determined gray-level in the converted image.

7. The method of claim 6, wherein the step of converting the original image further includes the steps of:

determining whether the percentage of the pixels in any of the gray-levels in the converted image is less than a gray threshold percentage and, if so, adjusting the gray-levels and then repeating the step of determining a second gray-scale representation of the pixels in the converted image using the adjusted gray-levels.

8. The method of claim 1, wherein the step of determining a color assigned to the pixels in each gray-level in the converted image includes the steps of:

for each gray-level in the converted image,

determining the colors in the original image of the pixels that were assigned to the gray-level in the converted image;

selecting the most prevalent color of the determined colors; and

assigning the selected color to the pixels in the gray-level in the converted image.

9. The method of claim 1,

wherein the converted image has two colors;

and

wherein the step of determining a second gray-scale representation of the pixels in the converted image includes the step of;

determining a black-and-white representation of the pixels in the converted image so that each pixel is colored either black or white in the converted image.

10. The method of claim 9, wherein the step of determining a black-and-white representation of the pixels in the converted image includes the step of:

for each pixel in the converted image, converting the first gray-scale representation of the pixel in the converted image into a black-and-white representation of the pixel in the converted image by determining whether the gray-value of the pixel in the converted image is greater than or equal to a gray threshold value and, if so, coloring the pixel white in the converted image, otherwise, coloring the pixel black in the converted image.

11. The method of claim 10, wherein the step of converting the original image further includes the steps of:

determining whether the percentage of the black pixels in the converted image is less than a black pixel threshold percentage and, if so, raising the gray threshold value used for coloring the pixels either black or white and then repeating the step of determining a black-and-white representation of the pixels in the converted image using the raised gray threshold value; and

determining whether the percentage of the white pixels in the converted image is less than a white pixel threshold percentage and, if so, lowering the gray threshold value used for coloring the pixels either black or white and then repeating the step of determining a black-and-white representation of the pixels in the converted image using the lowered gray threshold value.

12. The method of claim 11, wherein the step of determining a color assigned to the pixels in each gray-level in the converted image includes the steps of:

determining a color assigned to the black pixels in the converted image; and

determining a color assigned to the white pixels in the converted image.

13. The method of claim 12,

wherein the step of determining a color assigned to the black pixels in the converted image includes the steps of:

determining the colors in the original image of the pixels that were colored black in the converted image;

selecting the most prevalent color of the determined colors; and

assigning the selected color to the black pixels in the converted image; and

wherein the step of determining a color assigned to the white pixels in the converted image includes the steps of;

determining the colors in the original image of the pixels that were colored white in the converted image;

selecting the most prevalent color of the determined colors; and

assigning the selected color to the white pixels in the converted image.

14. The method of claim 13,

wherein each pixel in the original image has an opacity associated with the pixel;

wherein the step of converting the original image further includes the step of determining which pixels in the original image are opaque in the converted image by, for each pixel in the original image, determining whether the opacity of the pixel in the original image is greater than or equal to an opacity threshold value and, if so, making the pixel opaque in the converted image, otherwise, making the pixel transparent in the converted image;

wherein the step of determining a first gray-scale representation of the pixels in the converted image includes the step of determining a first gray-scale representation of the pixels that are opaque in the converted image; and

wherein the step of determining a black-and-white representation of the pixels in the converted image includes the step of determining a black-and-white representation of the pixels that are opaque in the converted image.

15. The method of claim 14,

wherein the specified representation of the converted image includes a foreground color, a background color, a source bitmap, and a mask bitmap, the source bitmap including a bit corresponding to each pixel in the converted image, and the mask bitmap including a bit corresponding to each pixel in the converted image;

and

wherein the step of specifying a representation of the converted image includes the step of specifying the foreground color, the background color, the source bitmap, and the mask bitmap of the converted image by;

assigning the color that was assigned to the black pixels in the converted image to the foreground color of the converted image;

assigning the color that was assigned to the white pixels in the converted image to the background color of the converted image;

setting the bits in the source bitmap corresponding to the pixels that were colored black in the converted image to "1" and setting the remaining bits to "0"; and

setting the bits in the mask bitmap corresponding to the pixels that were made opaque in the converted image to "1" and setting the remaining bits to "0".

16. The method of claim 1, wherein the original image and the converted image are cursors.

17. The method of claim 16, wherein the original image is a NEXTSTEP cursor and the converted image is an X11 cursor.

18. A computer program product for converting an image in a computer system, the computer program product comprising:

computer readable program code configured to receive an original image to be displayed, the original image including a plurality of pixels, each pixel having a color associated with the pixel;

computer readable program code configured to convert the original image into another image having fewer colors than the original image so that the converted image can be displayed including;

computer readable program code configured to determine a first gray-scale representation of the pixels in the converted image so that each pixel has a gray-value in the converted image;

computer readable program code configured to determine a second gray-scale representation of the pixels in the converted image so that each pixel is assigned to a gray-level in the converted image, wherein the number of gray-levels in the converted image is equal to the number of colors in the converted image;

computer readable program code configured to determine a color assigned to the pixels in each gray-level in the converted image; and

computer readable program code configured to specify a representation of the converted image using the determined second gray-scale representation and the determined colors; and

a computer readable medium in which the computer readable program codes are stored.

19. The computer program product of claim 18,

wherein each pixel in the original image has an opacity associated with the pixel;

wherein the computer readable program code configured to convert the original image further includes computer readable program code configured to determine which pixels in the original image are opaque in the converted image;

wherein the computer readable program code configured to determine a first gray-scale representation of the pixels in the converted image includes computer readable program code configured to determine a first gray-scale representation of the pixels that are opaque in the converted image; and

wherein the computer readable program code configured to determine a second gray-scale representation of the pixels in the converted image includes computer readable program code configured to determine a second gray-scale representation of the pixels that are opaque in the converted image.

20. The computer program product of claim 19, wherein the computer readable program code configured to determine which pixels in the original image are opaque in the converted image includes:

computer readable program code configured to, for each pixel in the original image, determine whether the opacity of the pixel in the original image is greater than or equal to an opacity threshold value and, if so, make the pixel opaque in the converted image, otherwise, make the pixel transparent in the converted image.

21. The computer program product of claim 20, wherein the computer readable program code configured to convert the original image further includes:

computer readable program code configured to determine whether the percentage of the opaque pixels in the converted image is less than an opaque pixel threshold percentage and, if so, lower the opacity threshold value used for making the pixels either opaque or transparent and then determine which pixels in the original image are opaque in the converted image using the lowered opacity threshold value; and

computer readable program code configured to determine whether the percentage of the transparent pixels in the converted image is less than a transparent pixel threshold percentage and, if so, raise the opacity threshold value used for making the pixels either opaque or transparent and then determine which pixels in the original image are opaque in the converted image using the raised opacity threshold value.

22. The computer program product of claim 18, wherein the computer readable program code configured to determine a first gray-scale representation of the pixels in the converted image includes:

computer readable program code configured to, for each pixel in the converted image, convert a color representation of the pixel in the original image into a first gray-scale representation of the pixel in the converted image.

23. The computer program product of claim 18, wherein the computer readable program code configured to determine a second gray-scale representation of the pixels in the converted image includes:

computer readable program code configured to, for each pixel in the converted image, convert the first gray-scale representation of the pixel in the converted image into a second gray-scale representation of the pixel in the converted image by determining in which gray-level the gray-value of the pixel in the converted image falls and assigning the determined gray-level to the pixel in the converted image.

24. The computer program product of claim 23, wherein the computer readable program code configured to convert the original image further includes:

computer readable program code configured to determine whether the percentage of the pixels in any of the gray-levels in the converted image is less than a gray threshold percentage and, if so, adjust the gray-levels and then determine a second gray-scale representation of the pixels in the converted image using the adjusted gray-levels.

25. The computer program product of claim 18, wherein the computer readable program code configured to determine a color assigned to the pixels in each gray-level in the converted image includes:

computer readable program code configured to, for each gray-level in the converted image,

determine the colors in the original image of the pixels that were assigned to the gray-level in the converted image;

select the most prevalent color of the determined colors; and

assign the selected color to the pixels in the gray-level in the converted image.

26. A system for converting an image in a computer system, the system comprising:

a computer configured to control the operation of the system;

a display device connected to said computer configured to display an image;

a secondary storage device connected to said computer; and

an image converter stored in said secondary storage device and executed by said computer, said image converter being configured to;

receive an original image to be displayed, the original image including a plurality of pixels, each pixel having a color associated with the pixel; and

convert the original image into another image having fewer colors than the original image so that the converted image can be displayed by;

determining a first gray-scale representation of the pixels in the converted image so that each pixel has a gray-value in the converted image;

determining a second gray-scale representation of the pixels in the converted image so that each pixel is assigned to a gray-level in the converted image, wherein the number of gray-levels in the converted image is equal to the number of colors in the converted image;

determining a color assigned to the pixels in each gray-level in the converted image; and

specifying a representation of the converted image using the determined second gray-scale representation and the determined colors.

27. The system of claim 26,

wherein each pixel in the original image has an opacity associated with the pixel;

and

wherein said image converter is further configured to;

determine which pixels in the original image are opaque in the converted image;

determine a first gray-scale representation of the pixels that are opaque in the converted image; and

determine a second gray-scale representation of the pixels that are opaque in the converted image.

28. The system of claim 27, wherein said image converter is further configured to:

for each pixel in the original image, determine whether the opacity of the pixel in the original image is greater than or equal to an opacity threshold value and, if so, make the pixel opaque in the converted image, otherwise, make the pixel transparent in the converted image.

29. The system of claim 28, wherein said image converter is further configured to:

determine whether the percentage of the opaque pixels in the converted image is less than an opaque pixel threshold percentage and, if so, lower the opacity threshold value used for making the pixels either opaque or transparent and then determine which pixels in the original image are opaque in the converted image using the lowered opacity threshold value; and

determine whether the percentage of the transparent pixels in the converted image is less than a transparent pixel threshold percentage and, if so, raise the opacity threshold value used for making the pixels either opaque or transparent and then determine which pixels in the original image are opaque in the converted image using the raised opacity threshold value.

30. The system of claim 26, wherein said image converter is further configured to:

for each pixel in the converted image, convert a color representation of the pixel in the original image into a first gray-scale representation of the pixel in the converted image.

31. The system of claim 26, wherein said image converter is further configured to:

for each pixel in the converted image, convert the first gray-scale representation of the pixel in the converted image into a second gray-scale representation of the pixel in the converted image by determining in which gray-level the gray-value of the pixel in the converted image falls and assigning the determined gray-level to the pixel in the converted image.

32. The system of claim 31, wherein said image converter is further configured to:

determine whether the percentage of the pixels in any of the gray-levels in the converted image is less than a gray threshold percentage and, if so, adjust the gray-levels and then determine a second gray-scale representation of the pixels in the converted image using the adjusted gray-levels.

33. The system of claim 26, wherein said image converter is further configured to:

for each gray-level in the converted image,

determine the colors in the original image of the pixels that were assigned to the gray-level in the converted image;

select the most prevalent color of the determined colors; and

assign the selected color to the pixels in the gray-level in the converted image.

34. The system of claim 26, wherein said computer is a stand-alone computer.

35. The system of claim 26, wherein said computer is connected to a network.