US4785356A — Apparatus and method of attenuating distortion in…

Claim 1

Independent Claim 175 words

In a gray level image data processor which includes (A) a predictive coder which (i) computes a predictive difference value D for the current pixel and (ii) quantizes the difference D to a QN value wherein the number of QN values is less than the number of permitted D values, and wherein ranges of larger D values correspond to QN values of relatively larger magnitudes wherein QN=Q0 corresponds to a region of substantially uniform gay level and (B) an entropy encoder which receives as input and compresses QN value data from the predictive coder, a machine-implemented method for reducing distortion in an image reconstructed from data subjected to compression by predicting coding, the method comprising the steps of: (a) for each pixel at which QN=Q0, setting a value QERR equal to D; (b) remapping the set QERR value to a value MERR; (c) summing the MERR values for successive pixels in a QN=Q0 region; and (d) for a pixel at which the sum of MERR values reaches a predefined threshold, adjusting the QN value thereof.

Claim 2

Dependent Claim 175 words

In a gray level image data processor which includes (A) a predictive coder which (i) computes a predictive difference value D for the current pixel and (ii) quantizes the difference D to a QN value wherein the number of QN values is less than the number of permitted D values, and wherein ranges of larger D values correspond to QN values of relatively larger magnitudes wherein QN=Q0 corresponds to a region of substantially uniform gay level and (B) an entropy encoder which receives as input and compresses QN value data from the predictive coder, a machine-implemented method for reducing distortion in an image reconstructed from data subjected to compression by predicting coding, the method comprising the steps of: (a) for each pixel at which QN=Q0, setting a value QERR equal to D; (b) remapping the set QERR value to a value MERR; (c) summing the MERR values for successive pixels in a QN=Q0 region; and (d) for a pixel at which the sum of MERR values reaches a predefined threshold, adjusting the QN value thereof.

Claim 3

Dependent Claim 41 words

The method of claim 1 wherein step (b) includes: (e) re-mapping QERR values to MERR values; and (f) assigning to the values MERR=0 those QERR value in which |QERR|≦(+Q1 VALUE)/2 where Q1 is the closest in value quantization level to Q0.

Claim 4

Dependent Claim 49 words

The method of claim 2 wherein step (e) includes the steps of: (g) re-mapping QERR=-4 and QERR=-3 to an MERR value of -1; (h) re-mapping QERR=-2, QERR=-1, QERR=0, QERR=1, and QERR=2 to an MERR value of 0; and (j) re-mapping QERR=3 and QERR=4 to an MERR value of 1.

Claim 5

Dependent Claim 36 words

The method of claim 2 wherein step (d) includes the steps of: (k) adjusting the QN value by the Q1 value when the sum reaches a predefined threshold; and (l) resetting the sum of MERR values.

Claim 6

Dependent Claim 80 words

The method of claim 4 comprising the further steps of: (m) reconstructing graylevel values for pixels in the image; and (n) filtering the reconstructed value I 0 for a current pixel to provide a filtered value of I' 0 which is equal to I.sub.0 +[(I.sub.-1 -I.sub.0).sub.C- +(I.sub.+1 -I.sub.0).sub.C+ ] wherein C+ and C- are respective predefined clamping values, and wherein I -1 and I +1 are the respective reconstructed values of pixels adjacently below and adjacently above the current pixel.

Claim 7

Dependent Claim 29 words

The method of claim 5 comprising the further step of: (p) repeating step (n) with one pixel after another in one alternating row after another being the current pixel.

Claim 8

Dependent Claim 185 words

A predictive coding encoder which supplies the output thereof to an entropy encoder, the predictive coding encoder comprising: means for computing a value D representing the difference between an original graylevel value for a current pixel and a predicted value for the current pixel; quantizer means for electronically associating each successive range of possible D values to a respective quantization level, each quantization level QN having a respective QN value representing the range corresponding thereto; switching means for setting a value QERR to D when QN=Q0 wherein Q0 represents the lowest quantization level; means for receiving QERR output from the switching means and re-mapping QERR values to MERR values so that the value MERR=0 assigned to those QERR values in which |QERR|≦(+Q1 VALUE)/2 wherein Q1 value is the value corresponding to the quantization level QN=Q1; means for summing the MERR values for successive pixels in a QN=Q0 region; and means for receiving as input the MERR value sum and adjusting the QN value from the value of Q0 by the magnitude of Q1 for a pixel at which the summed value reaches a predefined threshold.

Claim 9

Dependent Claim 185 words

A predictive coding encoder which supplies the output thereof to an entropy encoder, the predictive coding encoder comprising: means for computing a value D representing the difference between an original graylevel value for a current pixel and a predicted value for the current pixel; quantizer means for electronically associating each successive range of possible D values to a respective quantization level, each quantization level QN having a respective QN value representing the range corresponding thereto; switching means for setting a value QERR to D when QN=Q0 wherein Q0 represents the lowest quantization level; means for receiving QERR output from the switching means and re-mapping QERR values to MERR values so that the value MERR=0 assigned to those QERR values in which |QERR|≦(+Q1 VALUE)/2 wherein Q1 value is the value corresponding to the quantization level QN=Q1; means for summing the MERR values for successive pixels in a QN=Q0 region; and means for receiving as input the MERR value sum and adjusting the QN value from the value of Q0 by the magnitude of Q1 for a pixel at which the summed value reaches a predefined threshold.

Claim 10

Dependent Claim 101 words

A vertical filter for adjusting the reconstructed value I 0 for a current pixel in an image where the pixel adjacently above the current pixel has a value I +1 and the pixel adjacently below has a value I -1 , the filter comprising: means for computing a first difference (I -1 -I 0 ); means for computing a second difference (I +1 -I 0 ); means for clamping the first difference and second difference to prescribed limits; and means for computing a filtered value I' 0 for the current pixel to be equal to I.sub.0 +[(I.sub.-1 -I.sub.0).sub.C- +(I.sub.+1 -I.sub.0).sub.C+ ].

Claim 11

Dependent Claim 101 words

A vertical filter for adjusting the reconstructed value I 0 for a current pixel in an image where the pixel adjacently above the current pixel has a value I +1 and the pixel adjacently below has a value I -1 , the filter comprising: means for computing a first difference (I -1 -I 0 ); means for computing a second difference (I +1 -I 0 ); means for clamping the first difference and second difference to prescribed limits; and means for computing a filtered value I' 0 for the current pixel to be equal to I.sub.0 +[(I.sub.-1 -I.sub.0).sub.C- +(I.sub.+1 -I.sub.0).sub.C+ ].

Claim 12

Dependent Claim 84 words

The vertical filter as in claim 8 wherein said I' 0 computing means includes: means for interpolating the value of I -1 as ##EQU9## where I -2 is the value of a pixel two pixels down from the current pixel; means for interpolating the value of I +1 as ##EQU10## where I +2 is the value of a pixel two pixels up from the current pixel; and means for computing I' 0 based on the interpolated values of I -1 and I +1 .

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-11-15	1992-05-16	1992-11-15	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-11-15	1996-05-16	1996-11-15	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-11-15	2000-05-16	2000-11-15	$7700.00	Window Closed / Lapsed

Apparatus and method of attenuating distortion introduced by a predictive coding image compressor

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