US5649083A
Expired / Lapsed
US
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System and method for dithering and quantizing image data to optimize visual quality of a color recovered image
Assignee: Hewlett Packard Development Co LP
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Filing: 1994-04-15
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Granted: 1997-07-15
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Expires: 2014-04-15
Abstract
Abstract A color graphics pipeline has a separate encoder with a dither table for processing each color value in pixel data received from a host processor or rasterizer. The encoders modify color values and dither noise values and also combine both positive and negative dither noise values with the color values, for independent optimization of each color and for better edge detection in a color recovery filter within a decoder of the pipeline. Each encoder comprises the following elements. A comparator mechanism compares a color value with a predetermined cutoff value. A dither table provides dither noise values. An offset mechanism modifies the dither noise values to derive a modified dither noise value when the color value is greater than or equal to the predetermined cutoff value. An aliasing mechanism aliases the color value with other color values below the predetermined cutoff value to derive an aliased color value when the color value is less than the predetermined cutoff value. An adder mechanism adds the unmodified dither noise or modified dither noise to the aliased color value or nonaliased color value, respectively, to derive the dithered color value. A clamping mechanism ensures that the dithered color value resides within a predetermined color range. Finally, a quantizing mechanism quantizes the dithered color value to derive a quantized/dithered color value for storage in memory, such as in a frame buffer.
Inventors
- 👤 Anthony C. Barkans
- 👤 David L. McAllister
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 06:49
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/64; H04N1/648
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
165 words
A system for dithering and quantizing image data, comprising: dithering means for providing a dither noise value; comparator means for comparing a color value corresponding with the image data with a predetermined cutoff value; aliasing means for aliasing the color value with other color values below said predetermined cutoff value when the color value is less than said predetermined cutoff value to derive an aliased color value; offset means for modifying the dither noise value when the color value is greater than said predetermined cutoff value to derive a modified dither noise value; adder means for generating a dithered color value, said adder means for mathematically combining said dither noise value with said aliased color value and for mathematically combining said modified dither noise value with said color value; clamping means for insuring that said dithered color value resides within a predetermined color range; and quantizing means for quantizing said dithered color value to derive a dithered and quantized color value for storage in memory.
Claim 2
Independent Claim
165 words
A system for dithering and quantizing image data, comprising: dithering means for providing a dither noise value; comparator means for comparing a color value corresponding with the image data with a predetermined cutoff value; aliasing means for aliasing the color value with other color values below said predetermined cutoff value when the color value is less than said predetermined cutoff value to derive an aliased color value; offset means for modifying the dither noise value when the color value is greater than said predetermined cutoff value to derive a modified dither noise value; adder means for generating a dithered color value, said adder means for mathematically combining said dither noise value with said aliased color value and for mathematically combining said modified dither noise value with said color value; clamping means for insuring that said dithered color value resides within a predetermined color range; and quantizing means for quantizing said dithered color value to derive a dithered and quantized color value for storage in memory.
Claim 3
Dependent Claim
33 words
The system of claim 1, wherein said aliasing means comprises: means for dividing said color value by a constant to derive a quotient; and means for adding an integer number to said quotient.
Claim 4
Dependent Claim
10 words
The system of claim 2, wherein said constant is two.
Claim 5
Dependent Claim
14 words
The system of claim 1, wherein said color range comprises 256 different color intensities.
Claim 6
Dependent Claim
27 words
The system of claim 1, wherein said quantizing means further comprises a means for truncating said dithered color value to derive said dithered and quantized color value.
Claim 7
Dependent Claim
13 words
The system of claim 1, wherein said dithering means comprises a dither table.
Claim 8
Dependent Claim
16 words
The system of claim 1, wherein said dithering means comprises logic for generating said dither noise.
Claim 9
Dependent Claim
13 words
The system of claim 1, wherein said dither noise is a negative number.
Claim 10
Dependent Claim
32 words
The system of claim 1, wherein said dithering means includes a dither table corresponding with each of several colors, each said dither table having dither noise values corresponding with its respective color.
Claim 11
Independent Claim
164 words
A method for dithering and quantizing image data, comprising the steps of: generating dither noise; comparing a color value with a predetermined cutoff value; when the color value is greater than said predetermined cutoff value, modifying said dither noise to derive modified color noise; when the color value is less than said predetermined cutoff value, aliasing the color value with other color values below said predetermined cutoff value to derive an aliased color value; when the color value is greater than said predetermined cutoff value, mathematically combining said modified dither noise with said color value to derive a dithered color value; when the color value is less than said predetermined cutoff value, mathematically combining said dither noise with said aliased color value to derive said dithered color value; clamping said dithered color value to insure that said dithered color value resides within a predetermined color range; and quantizing said dithered color value to derive a dithered and quantized color value for storage in memory.
Claim 12
Independent Claim
164 words
A method for dithering and quantizing image data, comprising the steps of: generating dither noise; comparing a color value with a predetermined cutoff value; when the color value is greater than said predetermined cutoff value, modifying said dither noise to derive modified color noise; when the color value is less than said predetermined cutoff value, aliasing the color value with other color values below said predetermined cutoff value to derive an aliased color value; when the color value is greater than said predetermined cutoff value, mathematically combining said modified dither noise with said color value to derive a dithered color value; when the color value is less than said predetermined cutoff value, mathematically combining said dither noise with said aliased color value to derive said dithered color value; clamping said dithered color value to insure that said dithered color value resides within a predetermined color range; and quantizing said dithered color value to derive a dithered and quantized color value for storage in memory.
Claim 13
Dependent Claim
40 words
The method of claim 10, further comprising the step of averaging said dithered and quantized color value with other dithered and quantized color values corresponding to adjacent pixels to derive a decoded color value for display on a display device.
Claim 14
Dependent Claim
13 words
The method of claim 10, wherein the dither noise is a negative number.
Claim 15
Dependent Claim
41 words
The method of claim 10, wherein the step of aliasing further comprises the steps of: dividing said color value by a constant to derive a quotient; eliminating a fractional part of said quotient; and adding an integer number to said quotient.
Claim 16
Dependent Claim
10 words
The method of claim 13, wherein said constant is two.
Claim 17
Dependent Claim
14 words
The method of claim 10, wherein said color range comprises 256 different color intensities.
Claim 18
Dependent Claim
27 words
The method of claim 10, wherein said step of quantizing includes the step of truncating said dithered color value to derive said dithered and quantized color value.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-07-14 | 2001-01-13 | 2001-07-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-07-14 | 2005-01-13 | 2005-07-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-07-14 | 2009-01-13 | 2009-07-15 | $7700.00 | Window Closed / Lapsed |