Image discriminator

• US 6,097,845 A
• Filed: 10/21/1997
• Issued: 08/01/2000
• Est. Priority Date: 10/21/1997
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ng, Samson Y., Hochuli, Bruce E.
• Primary Examiner(s): Lee, Thomas D.
• Assistant Examiner(s): Chen, Wenpeng
• Application Number:
  US08/955,217
• Time in Patent Office: 1,015 Days
• Field of Search: 382/239, 382/232, 382/234, 382/168, 382/170, 382/171, 382/172, 382/250, 348/404-407, 348/419, 358/261.2, 358/430, 358/500
• US Class Current: 382/239
• 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: H04N 1/41 Bandwidth or redundancy reduction by scanning H04N1/17 ; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00

Abstract

A system and method for discriminating among image characteristics in order to select among a plurality of compression techniques. Multiple compression schemes are applied to a source image (101) concurrently and the results are stored. Image discrimination is performed in parallel with the image compression to generate a recommendation regarding the stored compressed images.

Claims

1. A system for discriminating among image characteristics in order to select among at least two compression techniques, the system comprising:

a first compressor for compressing a source image using a first compression method to obtain a first compressed image;

coupled to the first compressor, a first storage device for storing the first compressed image;

a second compressor for compressing the source image using a second compression method to obtain a second compressed image;

coupled to the second compressor, a second storage device for storing the second compressed image;

an image discriminator for characterizing the source image according to predefined criteria, and to generate and output a recommendation between the first and second compression methods; and

coupled to the image discriminator, the first storage device, and the second storage device an input device for accepting a user input signal to select between the first and second compression methods.

2. The system of claim 1, wherein the image discriminator and the first and second compressors operate concurrently on the source image.

3. The system of claim 1, wherein the image discriminator characterizes the source image according to relative quantity of grayscale content.

4. The system of claim 3, wherein:

the first compression method is optimized for grayscale image components; and

the second compression method is optimized for bitonal image components.

5. The system of claim 4, wherein the image discriminator characterizes the source image by performing a histogram analysis.

6. The system of claim 4, wherein:

the first compression method is a JPEG compression method; and

the second compression method is a bitonal compression method selected from the group consisting of JBIG, G3, and G4 compression methods.

7. The system of claim 1, wherein the image discriminator characterizes the source image according to relative quantity of color content.

8. The system of claim 1, wherein the source image is a moving image, and wherein the image discriminator characterizes the source image according to relative quantity of audio content.

9. The system of claim 1, further comprising a data switch coupled to the image discriminator, the first storage device, and the second storage device, for double-buffered storage of the compressed images and the recommendation.

10. The system of claim 1, wherein the image discriminator:

generates a preview of the image concurrently with operation of the first and second compressors; and

stores the generated preview.

11. The system of claim 10, further comprising a preview output device, coupled to the image discriminator, for displaying the generated preview.

24. The system of claim 5, wherein the image discriminator:

determines a luminance value for each pixel in the source image;

creates and fills a histogram of the luminance value of each pixel in the source image; and

analyzes the histogram of luminance values.

25. The system of claim 24, wherein the image discriminator analyzes the histogram of luminance values by:

determining a number of pixels in the source image with a mid-level luminance value; and

comparing the determined number with a predetermined threshold value.

26. The system of claim 1, further comprising:

coupled to at least one of the compressors, a scanner for accepting a document containing the source image.

12. A method of discriminating among image characteristics in order to select among at least two compression techniques, comprising:

a) compressing a source image using a first compression method to obtain a first compressed image;

b) storing the first compressed image;

c) compressing the source image using a second compression method to obtain a second compressed image;

d) storing the second compressed image;

e) characterizing the source image according to predefined criteria, and generating and outputting a recommendation between the first and second compression methods; and

f) accepting a user input to select between the first and second compression methods.

13. The method of claim 12, wherein a), c), and e) are performed concurrently.

14. The method of claim 12, wherein e) comprises characterizing the source image according to relative quantity of grayscale content.

15. The method of claim 14, wherein:

a) comprises compressing the source image using a compression method optimized for grayscale image components; and

c) comprises compressing the source image using a compression method optimized for bitonal image components.

16. The method of claim 15, wherein e) comprises characterizing the source image by performing a histogram analysis.

17. The method of claim 15, wherein the source image comprises a plurality of pixels, and wherein e) comprises:

e.1) determining a luminance value for each pixel in the source image;

e.2) for each pixel in the source image, incrementing a counter corresponding to the determined luminance value;

e.3) constructing a histogram from the counters; and

e.4) analyzing the constructed histogram to characterize the source image.

18. The method of claim 14, wherein:

a) comprises compressing the source image using a JPEG compression method; and

c) comprises compressing the source image using a bitonal compression method selected from the group consisting of JBIG, G3, and G4 compression methods.

19. The method of claim 12, wherein e) comprises characterizing the source image according to relative quantity of color content.

20. The method of claim 12, wherein the source image is a moving image, and wherein e) comprises characterizing the source image according to relative quantity of audio content.

21. The method of claim 12, further comprising:

g) concurrently with a) and c), generating a preview of the image; and

h) storing the generated preview.

22. The method of claim 21, further comprising:

i) displaying the generated preview.

23. The method of claim 17, wherein e.4) comprises:

determining a number of pixels in the source image with a mid-level luminance value; and

comparing the determined number with a predetermined threshold value.

27. The method of claim 12, further comprising:

prior to compressing the source image, scanning a document to obtain the source image.