Image format conversion with transparency color adjustment

• US 6,211,881 B1
• Filed: 08/12/1998
• Issued: 04/03/2001
• Est. Priority Date: 05/13/1998
• Status: Expired due to Term

• Current Assignee: Palo Alto Networks Incorporated
• Original Assignee: Compaq Computer Corporation (HP Inc.)
• Inventors: Starnes, Darrell J., Gabler, Jeffrey R.
• Primary Examiner(s): Vo, Cliff N.
• Application Number:
  US09/133,514
• Time in Patent Office: 965 Days
• Field of Search: 345/418, 345/431, 345/433, 345/438, 345/439
• US Class Current: 345/418
• CPC Class Codes: G06T 17/00 Three dimensional [3D] modelling, e.g. data description of 3D objects
• CPC Class Codes: G06T 9/00 Image coding bandwidth or redundancy reduction for static pictures H04N1/41; coding or decoding of static colour picture signals H04N1/64; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00
• CPC Class Codes: G06V 30/1423 the instrument generating sequences of position coordinates corresponding to handwriting preprocessing or recognising digital ink G06V30/32
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]

Abstract

Improved image format conversion techniques that provide improved conversion from an image format supporting transparency to an image format not supporting transparency. The techniques replace a transparency color in an original image format prior to format conversion. Consequently, the format conversion uses the replacement transparency color instead of the original transparency color, and thus is able to provide improved image conversion when converting from an image format supporting transparency to an image format not supporting transparency.

Claims

1. A method for converting a source image file having a first image format to a target image having a second image format, the method comprising the acts of:

(a) determining whether the source image file having the first image format uses at least one transparent portion;

(b) receiving a color table from the source image file;

(c) identifying a transparent color for the at least one transparent portion from the color table;

(d) determining a replacement transparent color for use with the target image having the second image format;

(e) modifying the color table by substituting the replacement transparent color for the transparent color; and

(f) thereafter converting the source image file having the first image format to the target image file having the second image format in accordance with the modified color table.

2. A method as recited in claim 1, wherein the first image format is a GIF format and the second image format is a JPEG format.

3. A method as recited in claim 1, wherein the determining (d) of the replacement transparent color comprises identifying a predetermined color.

4. A method as recited in claim 1, wherein the determining (d) of the replacement transparent color comprises:

determining a background color to be displayed behind the target image on a display screen; and

setting the replacement transparent color to the background color.

5. A method as recited in claim 1, wherein the method further comprises:

(g) bypassing acts (c)-f) when the determining (a) determines that the source image lacks at least one transparent portion, and converting the source image file having the first image format to the target image file having the second image format in accordance with the color table.

6. A method for converting a source image file having a first image format to a target image having a second image format, the method being performed by a computer system including a memory, the method comprising the acts of:

(a) allocating a memory block in the memory of the computer system;

(b) reading a header block from the source image file;

(c) reading a logical screen descriptor block from the source image file;

(d) determining whether a color table is present in the source image file;

(e) reading the color table into the memory block when the determining (d) determines that the color table is present in the source image file;

(f) reading a graphic control block for an image block in the source image file;

(g) determining whether transparency is used in the image block by an examination of the graphic control block;

(h) identifying a transparent color index for the color table;

(i) determining a replacement transparent color for use with the target image having the second image format, where the second image format does not support transparency;

(j) modifying the color table by substituting the replacement transparent color for the transparent color; and

(k) thereafter converting the source image file having the first image format to the target image file having the second image format in accordance with the modified color table.

7. A method as recited in claim 6, wherein the first image format is a GIF format and the second image format is a JPEG format.

8. A method as recited in claim 6, wherein the determining (i) of the replacement transparent color comprises identifying a predetermined color.

9. A method as recited in claim 6, wherein the determining (i) of the replacement transparent color comprises:

determining a background color to be displayed behind the target image on a display screen; and

setting the replacement transparent color to the background color.

10. A computer readable medium containing computer program code for converting a source image file having a first image format to a target image having a second image format, said computer readable medium comprising:

computer program code for receiving the source image file having with the first image format that uses at least one transparent portion;

computer program code for receiving a color table from the source image file;

computer program code for identifying a transparent color for the at least one transparent portion from the color table;

computer program code for determining a replacement transparent color for use with the target image having the second image format;

computer program code for modifying the color table by substituting the replacement transparent color for the transparent color; and

computer program code for converting the source image file having the first image format to the target image file having the second image format in accordance with the modified color table.

11. A computer readable medium method as recited in claim 10, wherein the first image format is a GIF format and the second image format is a JPEG format.

12. A computer readable medium as recited in claim 10, wherein said computer program code for determining the replacement transparent color comprises computer program code for identifying a predetermined color.

13. A computer readable medium as recited in claim 12, wherein said computer program code for determining the replacement transparent color comprises:

computer program code for determining a background color to be displayed behind the target image on a display screen; and

computer program code for setting the replacement transparent color to the background color.

14. A computer readable medium as recited in claim 10, wherein said computer program code for determining the replacement transparent color comprises:

computer program code for determining a background color to be displayed behind the target image on a display screen; and

computer program code for setting the replacement transparent color to the background color.

15. A computer readable medium as recited in claim 14, wherein said computer readable medium further comprises:

computer program code for bypassing said computer program code for identifying, said computer program code for determining, said computer program code for modifying and said computer program code for converting acts when the source image lacks at least one transparent portion, and converting the source image file having the first image format to the target image file having the second image format in accordance with the color table.

16. A computer readable medium as recited in claim 10, wherein said computer readable medium further comprises:

computer program code for bypassing said computer program code for identifying, said computer program code for determining, said computer program code for modifying and said computer program code for converting acts when the source image lacks at least one transparent portion, and converting the source image file having the first image format to the target image file having the second image format in accordance with the color table.

17. A computer readable medium as recited in claim 16, wherein said computer readable medium is one of a data storage disk, a carrier wave, and an integrated circuit.

18. A computer readable medium method as recited in claim 17, wherein the first image format is a GIF format and the second image format is a JPEG format.

19. A computer readable medium as recited in claim 10, wherein said computer readable medium is one of a data storage disk, a carrier wave, and an integrated circuit.