Elimination of visible quantizing artifacts in a digital image utilizing a critical noise/quantizing factor

• US 5,809,178 A
• Filed: 06/11/1996
• Issued: 09/15/1998
• Est. Priority Date: 06/11/1996
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Anderson, Eric C., Dalke, George W.
• Primary Examiner(s): ROGERS, SCOTT A
• Application Number:
  US08/661,524
• Time in Patent Office: 826 Days
• Field of Search: 382/268, 382/251, 382/239, 382/248, 382/250, 382/266, 382/275, 358/445, 358/463, 358/432, 358/433, 358/430, 348/403, 348/404, 348/405, 348/406, 348/420, 348/424, 348/425, 348/419
• US Class Current: 382/251
• CPC Class Codes: H04N 1/40 Picture signal circuits H04N1/387 takes precedence
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/147 according to rate distortion criteria rate-distortion as a criterion for motion estimation H04N19/567
• CPC Class Codes: H04N 19/154 Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion use of rate-distortion criteria H04N19/147
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness
• CPC Class Codes: H04N 5/21 Circuitry for suppressing or minimising disturbance, e.g. moiré or halo

Abstract

A method and system eliminates visible quantizing artifacts in a digital image. The present invention eliminates visible artifacts by determining a function descriptive of a noise model for an input source of image data, utilizing a critical noise/quantizing factor in conjunction with the noise model function to determine a quantization function, and deriving optimum coding for the image data from the quantization function to produce digital image data lacking visible quantization artifacts. The critical noise/quantizing factor is a constant value found to be a value of 3/8. The present invention further includes deriving inverse coding for the optimum coding to allow processing of the digital image.

Claims

1. A method for eliminating visible quantizing artifacts in a digital image, the method comprising:

(a) determining a function descriptive of a noise model for an input source of image data;

(b) utilizing a critical noise/quantizing factor in conjunction with the noise model function to determine a quantization function; and

(c) deriving optimum coding for the image data from the quantization function to produce digital image data lacking visible quantization artifacts.

2. The method of claim 1 wherein the critical noise/quantizing factor is a constant value.

3. The method of claim 2 wherein the constant value is 3/8.

4. The method of claim 1 further comprising deriving inverse coding for the optimum coding to allow processing of the digital image.

5. The method of claim 1 wherein the utilizing step (b) further comprises the step of (b1) determining the critical noise/quantizing factor.

6. A method for eliminating visible quantizing artifacts in a digital image, the method comprising:

(a) determining a function descriptive of a noise model for an input source of image data;

(b) utilizing a critical noise/quantizing factor in conjunction with the noise model function to determine a quantization function including determining the critical noise/quantizing factor by

obtaining an input image of sufficient precision;

adding noise to the input image of known distribution; and

quantizing the input image into successively larger quantizing intervals until a quantizing artifact becomes visible, wherein the quantizing interval revealing the quantizing artifact is the critical quantizing interval; and

(c) deriving optimum coding for the image data from the quantization function to produce digital image data lacking visible quantization artifacts.

7. The method of claim 6 further comprising the step of applying a plurality of brightness and contrast transforms before the quantizing step.

8. A system for eliminating visible quantizing artifacts in a digital image, the system comprising:

a circuit for;

determining a function descriptive of a noise model for an input source of image data;

utilizing a critical noise/quantizing factor in conjunction with the noise model function to determine a quantization function; and

deriving optimum coding for the image data from the quantization function to produce digital image data lacking visible quantization artifacts.

9. The system of claim 8 wherein the critical noise/quantizing factor is a constant value.

10. The system of claim 9 wherein the constant value is 3/8.

11. The system of claim 8 further comprising deriving inverse coding for the optimum coding to allow processing of the digital image.

12. The system of claim 8 wherein the input source comprises a digital camera.

13. The system of claim 8 wherein the input source comprises a scanner.

14. The system of claim 8 wherein a CRT outputs the digital image produced.

15. The system of claim 8 wherein a printer outputs the digital image produced.

16. The system of claim 8 wherein utilizing the critical noise/quantizing factor further comprises determining the critical noise/quantizing factor.

17. A system for eliminating visible quantizing artifacts in a digital image, the system comprising:

a circuit for;

determining a function descriptive of a noise model for an input source of image data;

utilizing a critical noise/quantizing factor in conjunction with the noise model function to determine a quantization function including determining the critical noise/quantizing factor by obtaining an input image of sufficient precision;

adding noise to the input image of known distribution; and

quantizing the input image into successively larger quantizing intervals until a quantizing artifact becomes visible, wherein the quantizing interval revealing the quantizing artifact is the critical quantizing interval; and

deriving optimum coding for the image data from the quantization function to produce digital image data lacking visible quantization artifacts.

18. The system of claim 17 further comprising the step of applying an exhaustive variety of brightness and contrast transforms before quantizing the input image.