US5130786A
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Color image compression processing with compensation
Assignee: Raytheon Co
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Filing: 1989-09-12
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Granted: 1992-07-14
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Expires: 2009-09-12
Abstract
Abstract A method of color image compression processing provides compensation for lossy luminance compression (30) by adjusting (34) the red and blue color components using a lossy luminance compression factor equal to the difference between compressed and decompressed luminance. The compensated color components are then used to compute (42) chrominance color differences. Chrominance is range compressed (44) by bit-reduction using a non-linear range compression function that minimizes compression for small chrominance magnitudes, where the eye is more sensitive to a loss of color fidelity, while maximizing compression in the color saturation regions where the eye is less sensitive. After luminance and chrominance decompression (60) and reconversion to the RBG color components (70), compensation for red and blue color shift (such as due to round-off errors) is accomplished by multiplying (80) the green component (which is calculated from the color-shifted red and blue components) by a color shift compensation factor that shifts green in the opposite direction from the shift in the red and blue components.
Inventors
- 👤 Richard Y. Murata
- 👤 Harry S. Pyle
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 20:25
CPC Classifications
G; G06; G06T; G06T9/00; G06T9/005; H; H04; H04N; H04N11/00; H04N11/04; H04N11/042
Claims Analysis
Total Claims: 54
Claim 1
Independent Claim
94 words
A color image processing method for encoding and decoding color images formed by pixels with each pixel being defined by separate color components, comprising the steps: receiving a color image including color component data for each pixel; converting the color component data to corresponding luminance and chrominance component data; and range compressing the chrominance data by bit-reduction according to a non-linear range compression function in which, for small chrominance magnitudes, compressed chrominance magnitudes are substantially equal to actual chrominance magnitudes, and for large chrominance magnitudes, the compression of chrominance magnitudes increases to a maximum.
Claim 2
Dependent Claim
94 words
A color image processing method for encoding and decoding color images formed by pixels with each pixel being defined by separate color components, comprising the steps: receiving a color image including color component data for each pixel; converting the color component data to corresponding luminance and chrominance component data; and range compressing the chrominance data by bit-reduction according to a non-linear range compression function in which, for small chrominance magnitudes, compressed chrominance magnitudes are substantially equal to actual chrominance magnitudes, and for large chrominance magnitudes, the compression of chrominance magnitudes increases to a maximum.
Claim 3
Dependent Claim
57 words
The color image processing method of claim 1, wherein the non-linear range compression function is substantially m.sub.C =S[r.sup.m -1]/[r-1] where m is a chrominance magnitude, S is a compression/expansion factor, r is a range compression factor less than one and greater than zero, and m C is the resulting compressed chrominance magnitude rounded to the nearest integer.
Claim 4
Dependent Claim
42 words
The color image processing method of claim 2, wherein the step of range compressing chrominance is performed by computing the compressed chrominance magnitude m C for each possible chrominance magnitude m, and storing the m C values in a table for look-up.
Claim 5
Dependent Claim
26 words
The color image processing method of claim 1, wherein chrominance is derived from color differences C-Y, where C is a color component, and Y is luminance.
Claim 6
Dependent Claim
50 words
The color image processing method of claim 4, wherein a color image is defined by RGB color components, and wherein the chrominance components are RD=R-Y BD=B-Y where Y is luminance, R and B are red and blue color components, and RD and BD are corresponding red and blue color differences.
Claim 7
Dependent Claim
23 words
The color image processing method of claim 5, wherein chrominance has N magnitude bits, and wherein range compressed chrominance has N-1 magnitude bits.
Claim 8
Dependent Claim
56 words
The color image processing method of claim 4, wherein the non-linear range compression function is substantially m.sub.C =S[r.sup.m -1]/[r-1] where m is a chrominance magnitude, S is a compression/expansion factor, r is a progression factor less than one and greater than zero, and m C is the resulting compressed chrominance magnitude rounded to the nearest integer.
Claim 9
Dependent Claim
56 words
The color image processing method of claim 7, wherein the step of range compressing chrominance is performed by: determining the chrominance component that has the largest range; computing the compressed chrominance magnitude for each such possible chrominance magnitude; and storing the m C values in a table for look-up in determining all compressed chrominance component magnitudes.
Claim 10
Dependent Claim
51 words
The color image processing method of claim 8, wherein the color image is defined by RGB color components, and wherein the chrominance components are RD=R-Y BD=B-Y where Y is luminance, R and B are red and blue color components, and RD and BD are the corresponding red and blue color differences.
Claim 11
Dependent Claim
23 words
The color image processing method of claim 9, wherein chrominance has N magnitude bits, and wherein range compressed chrominance has N-1 magnitude bits.
Claim 12
Dependent Claim
53 words
The color image processing method of claim 7, wherein the step of range compressing chrominance is performed by: for each chrominance component, calculating the range compressed chrominance magnitude m C for each possible chrominance magnitude; and storing the m C values in respective tables for look-up in determining the corresponding chrominance component magnitudes.
Claim 13
Dependent Claim
49 words
The color image processing method of claim 11, wherein the color image is defined by RGB color components, and wherein the chrominance components are RD=R-Y BD=B-Y where Y is luminance, R and B are red and blue color components, and RD and BD are red and blue color differences.
Claim 14
Dependent Claim
24 words
The color image processing method of claim 12, wherein chrominance has N magnitude bits, and wherein each range compressed chrominance has N-1 magnitude bits.
Claim 15
Dependent Claim
17 words
The color image processing method of claim 1, further comprising the step of compressing the luminance data.
Claim 16
Dependent Claim
71 words
The color image processing method of claim 14, wherein luminance compression is lossy, and further comprising, prior to the step of range compressing chrominance, the step of compensating for lossy luminance compression by adjusting the color components used to derive chrominance according to a lossy compression compensation function in which the compensated color component magnitude is obtained using a luminance error factor corresponding to the difference between uncompressed and decompressed luminance.
Claim 17
Dependent Claim
46 words
The color image processing method of claim 15, wherein the lossy compression compensation function is substantially C'=C+d(Y-Y') where C is a color component, d is a percentage weighting factor, Y is uncompressed luminance, Y' is decompressed luminance, and C' is the corresponding compensated color component magnitude.
Claim 18
Dependent Claim
29 words
The color image processing method of claim 16, wherein chrominance is derived from color differences C'-Y', where C' is a compensated color component magnitude, and Y' is decompressed luminance.
Claim 19
Dependent Claim
70 words
The color image processing method of claim 17, wherein a color image is defined by RGB color components, wherein the compensated color component magnitudes are given by the lossy compression compensation functions R'=R+(Y-Y') B'=B+(Y-Y') wherein chrominance is given by the compensated color differences R'D=R'-Y' B'D=B'-Y' where Y' is decompressed luminance, R' and B' are the compensated red and blue color components, and R'D and B'D are corresponding compensated color differences.
Claim 20
Dependent Claim
74 words
The color image processing method of claim 1, further comprising the steps of: reconverting luminance and chrominance to corresponding color components; and computing a complementary color component using the reconverted color components; compensating for color shift caused by errors in the reconverted color components by adjusting the complementary color component according to a color shift compensation function in which the compensated complementary color component is directly proportional to the corresponding uncompensated complementary color component.
Claim 21
Dependent Claim
51 words
The color image processing method of claim 19, wherein: each pixel is defined by at least three color components, one of which is designated a complementary color component; luminance is derived from the color components; and chrominance is derived from luminance and the color components other than the complementary color component.
Claim 22
Dependent Claim
90 words
The color image processing method of claim 20: wherein a color image is defined by RGB color components, with green being designated the complementary color component such that chrominance is derived from luminance and the red and blue color components; and wherein the step of compensating for color shift is performed by adjusting the green color component according to the color shift compensation function G'=kG where G is the uncompensated green color component, k is a color shift factor around one, and G' is the corresponding compensated green color component.
Claim 23
Dependent Claim
103 words
A color image processing method for encoding and decoding color images formed by pixels with each pixel being defined by separate color components, comprising the steps: receiving a color image including color component data for each pixel; converting the color component data to corresponding luminance and chrominance component data; compressing the luminance data using a lossy compression algorithm; and compensating for lossy luminance compression by adjusting the color components used to derive chrominance according to a lossy compression compensation function in which the compensated color component magnitude is obtained using a luminance error factor corresponding to the difference between uncompressed and decompressed luminance.
Claim 24
Dependent Claim
103 words
A color image processing method for encoding and decoding color images formed by pixels with each pixel being defined by separate color components, comprising the steps: receiving a color image including color component data for each pixel; converting the color component data to corresponding luminance and chrominance component data; compressing the luminance data using a lossy compression algorithm; and compensating for lossy luminance compression by adjusting the color components used to derive chrominance according to a lossy compression compensation function in which the compensated color component magnitude is obtained using a luminance error factor corresponding to the difference between uncompressed and decompressed luminance.
Claim 25
Dependent Claim
45 words
The color image processing method of claim 22, wherein the lossy compression compensation function is substantially C'=C+d(Y-Y') where C is a color component, d is a weighting factor, Y is uncompressed luminance, Y' is decompressed luminance, and C' is the corresponding compensated color component magnitude.
Claim 26
Dependent Claim
30 words
The color image processing method of claim 23, wherein chrominance is derived from compensated color differences C'-Y', where C' is a compensated color component magnitude, and Y' is decompressed luminance.
Claim 27
Dependent Claim
71 words
The color image processing method of claim 24: wherein a color image is defined by RGB color components, wherein the compensated color component magnitudes are given by the lossy compression compensation functions R'=R+(Y-Y') B'=B+(Y-Y') and wherein chrominance is given by the compensated color differences R'D=R'-Y' B'D=B'-Y' where Y' is decompressed luminance, R' and B' are the compensated red and blue color components, and R'D and B'D are corresponding compensated color differences.
Claim 28
Dependent Claim
46 words
The color image processing method of claim 22, further comprising the step of range compressing the chrominance data by bit-reduction according to a non-linear range compression function in which compression is a minimum for small chrominance magnitudes and increases to a maximum for large chrominance magnitudes.
Claim 29
Dependent Claim
30 words
The color image processing method of claim 26, wherein, for small chrominance magnitudes, the non-linear range compression function yields compressed chrominance magnitudes that are equal to the actual chrominance magnitude.
Claim 30
Dependent Claim
57 words
The color image processing method of claim 29, wherein the non-linear range compression function is substantially m.sub.C =S[r.sup.m -1]/[r-1] where m is a chrominance magnitude, S is a compression/expansion factor, r is a range compression factor less than one and greater than zero, and m C is the resulting compressed chrominance magnitude rounded to the nearest integer.
Claim 31
Dependent Claim
42 words
The color image processing method of claim 28, wherein the step of range compressing chrominance is performed by computing the compressed chrominance magnitude m C for each possible chrominance magnitude m, and storing the m C values in a table for look-up.
Claim 32
Dependent Claim
22 words
The color image processing method of claim 29, wherein chrominance has N magnitude bits, and wherein compressed chrominance has N-1 magnitude bits.
Claim 33
Dependent Claim
57 words
The color image processing method of claim 29, wherein the step of range compressing chrominance is performed by: determining the chrominance component that has the largest range; computing the compressed chrominance magnitude m C for each such possible chrominance magnitude; and storing the m C values in a table for look-up in determining all compressed chrominance magnitudes.
Claim 34
Dependent Claim
51 words
The color image processing method of claim 29, wherein the step of range compressing chrominance is performed by: for each chrominance component, calculating the compressed chrominance magnitude m C for each possible chrominance magnitude; and storing the m C values in respective tables for look-up in determining the corresponding chrominance magnitudes.
Claim 35
Dependent Claim
75 words
The color image processing method of claim 22, further comprising the steps: reconverting the luminance and chrominance components to corresponding color components; computing a complementary color component using the reconverted color components; and compensating for color shift caused by errors in the reconverted color components by adjusting the complementary color component according to a color shift compensation function in which the compensated complementary color component is directly proportional to the corresponding uncompensated complementary color component.
Claim 36
Dependent Claim
50 words
The color image processing method of claim 33, wherein each pixel is defined by at least three color components, one of which is designated a complementary color component; luminance is derived from the color components chrominance is derived from luminance and the color components other than the complementary color component.
Claim 37
Dependent Claim
92 words
The color image processing method of claim 34: wherein a color image is defined by RGB color components, with green being designated the complementary color component such that chrominance is derived from luminance and the red and blue color components; and wherein the step of compensating for color shift is performed by adjusting the green color component according to the color shift compensation function G'=kG where G is the uncompensated green color component, k is a color shift factor about equal to one, and G' is the corresponding compensated green color component.
Claim 38
Dependent Claim
110 words
A color image processing method for encoding and decoding color images formed by pixels with each pixel being defined by separate color components, comprising the steps: receiving a color image including color component data for each pixel; converting the color component data to corresponding luminance and chrominance component data; reconverting luminance and chrominance to corresponding color components; computing a complementary color component using the reconverted color components; and compensating for color shift caused by errors in the reconverted color components by adjusting the complementary color component according to a color shift compensation function in which the compensated complementary color component is directly proportional to the corresponding uncompensated complementary color component.
Claim 39
Dependent Claim
110 words
A color image processing method for encoding and decoding color images formed by pixels with each pixel being defined by separate color components, comprising the steps: receiving a color image including color component data for each pixel; converting the color component data to corresponding luminance and chrominance component data; reconverting luminance and chrominance to corresponding color components; computing a complementary color component using the reconverted color components; and compensating for color shift caused by errors in the reconverted color components by adjusting the complementary color component according to a color shift compensation function in which the compensated complementary color component is directly proportional to the corresponding uncompensated complementary color component.
Claim 40
Dependent Claim
50 words
The color image processing method of claim 36, wherein: each pixel is defined by at least three color components, one of which is designated a complementary color component; luminance is derived from the color components; chrominance is derived from luminance and the color components other than the complementary color component.
Claim 41
Dependent Claim
92 words
The color image processing method of claim 37: wherein a color image is defined by RGB color components, with green being designated the complementary color component such that chrominance is derived from luminance and the red and blue color components; and wherein the step of compensating for color shift is performed by adjusting the green color component according to the color shift compensation function G'=kG where G is the uncompensated green color component, k is a color shift factor about equal to one, and G' is the corresponding compensated green color component.
Claim 42
Dependent Claim
46 words
The color image processing method of claim 36, further comprising the step of range compressing the chrominance data by bit-reduction according to a non-linear range compression function in which compression is a minimum for small chrominance magnitudes and increases to a maximum for large chrominance magnitudes.
Claim 43
Dependent Claim
30 words
The color image processing method of claim 39, wherein, for small chrominance magnitudes, the non-linear range compression function yields compressed chrominance magnitudes that are equal to the actual chrominance magnitude.
Claim 44
Dependent Claim
57 words
The color image processing method of claim 40, wherein the non-linear range compression function is substantially m.sub.C =S[r.sup.m -1]/[r-1] where m is a chrominance magnitude, S is a compression/expansion factor, r is a range compression factor less than one and greater than zero, and m C is the resulting compressed chrominance magnitude rounded to the nearest integer.
Claim 45
Dependent Claim
42 words
The color image processing method of claim 41, wherein the step of range compressing chrominance is performed by computing the compressed chrominance magnitude m C for each possible chrominance magnitude m, and storing the m C values in a table for look-up.
Claim 46
Dependent Claim
22 words
The color image processing method of claim 42, wherein chrominance has N magnitude bits, and wherein compressed chrominance has N-1 magnitude bits.
Claim 47
Dependent Claim
56 words
The color image processing method of 42, wherein the step of range compressing chrominance is performed by: determining the chrominance component that has the largest range; computing the compressed chrominance magnitude m C for each such possible chrominance magnitude; and storing the m C values in a table for look-up in determining all compressed chrominance magnitudes.
Claim 48
Dependent Claim
56 words
The color image processing method of 42, wherein the step of range compressing chrominance is performed by: determining the chrominance component that has the largest range; computing the compressed chrominance magnitude m C for each such possible chrominance magnitude; and storing the m C values in a table for look-up in determining all compressed chrominance magnitudes.
Claim 49
Dependent Claim
51 words
The color image processing method of claim 42, wherein the step of range compressing chrominance is performed by: for each chrominance component, calculating the compressed chrominance magnitude m C for each possible chrominance magnitude; and storing the m C values in respective tables for look-up in determining the corresponding chrominance magnitudes.
Claim 50
Dependent Claim
17 words
The color image processing method of claim 36, further comprising the step of compressing the luminance data.
Claim 51
Dependent Claim
71 words
The color image processing method of claim 46, wherein luminance compression is lossy, and further comprising, prior to the step of range compressing chrominance, the step of compensating for lossy luminance compression by adjusting the color components used to derive chrominance according to a lossy compression compensation function in which the compensated color component magnitude is obtained using a luminance error factor corresponding to the difference between uncompressed and decompressed luminance.
Claim 52
Dependent Claim
45 words
The color image processing method of claim 47, wherein the lossy compression compensation function is substantially C'=C+d(Y-Y') where C is a color component, d is a weighting factor, Y is uncompressed luminance, Y' is decompressed luminance, and C' is the corresponding compensated color component magnitude.
Claim 53
Dependent Claim
30 words
The color image processing method of claim 48, wherein chrominance is derived from compensated color differences C'-Y', where C' is a compensated color component magnitude, and Y' is decompressed luminance.
Claim 54
Dependent Claim
71 words
The color image processing method of claim 49: wherein a color image is defined by RGB color components, wherein the compensated color component magnitudes are given by the lossy compression compensation functions R'=R+(Y-Y') B'=B+(Y-Y') and wherein chrominance is given by the compensated color differences R'D=R'-Y' B'D=B'-Y' where Y' is decompressed luminance, R' and B' are the compensated red and blue color components, and R'D and B'D are corresponding compensated color differences.
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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) | 1995-07-14 | 1996-01-13 | 1996-07-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-07-14 | 2000-01-13 | 2000-07-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-07-14 | 2004-01-13 | 2004-07-14 | $7700.00 | Window Closed / Lapsed |