Patent ID: 8274705

Claim:
A method of diffusing tone quantization error of a digital image comprising: receiving a digital image having input pixel tone levels for one or more color channels according to i rows and j columns; for alternate rows of pixels of the digital image: quantizing an assigned pixel tone level of each pixel, or S i,j , per color channel, in series j based on an integer downsizing, wherein the assigned tone level, or S i,j , comprises an input tone value, or P i,j , and, a partial tone quantization error, or N i,j−1 , from the last quantized pixel in row i, if present; and determining for each pixel in series j of the alternate rows of pixels, and per color channel, a total quantization error, or D i,j , based on the assigned pixel tone level of the pixel, or S i,j , and the quantized assigned pixel tone level of the pixel, or Q i,j , wherein the total quantization error, or D i,j ,comprises a partial tone quantization error, or N i,j , and a remainder tone quantization error, or E i,j ; and storing, per color channel, the remainder tone quantization error, or E i,j ; and for rows of pixels interposed between the alternate rows of pixels of the digital image: quantizing an assigned pixel tone level of each pixel, or S i,j , per color channel, in series j based on an integer downsizing, wherein the assigned tone level, or S i,j ,comprises: (a) an input tone value, or P i,j ; (b) a partial tone quantization error, or N i,j−1 , from the last quantized pixel in row i, if present; and (c) a sum of a weighted remainder tone quantization errors of two or more of the nearest neighbor pixels of the alternate rows comprising the sum: w 2 *E i−1,j +w 5 *E i+1,j +w 6 *E i+1,j+1 and, at least one of: (i) the sum: w 1 *E i−1,j−1 +w 4 *E i−1,j−1 and (ii) the sum: w 3 *E i−1,j+1 +w 6 *E i+1,j+1 , wherein w 1 ,w 2 , w 3 , w 4 , w 5 , and w 6 , are weighted apportionments given to a set of tone quantization error remainders; and determining, for each pixel in series j of the rows of pixels interposed between the alternate rows of pixels, and per color channel, a total quantization error, or D i,j , based on the assigned pixel tone level of the pixel, or S i,j , and the quantized assigned pixel tone level of the pixel, or Q i,j , wherein the total quantization error, or D i,j , comprises a partial tone quantization error, or N i,j .