Patent ID: 8035860

Claim:
A method for processing FM-AM mixed halftone images on a multi-bit depth imaging apparatus, comprising: 1) dividing averagely an interval [0, 255] into 2 n +1 gradations in light of a bit depth n of the apparatus: [0, R 1 ], (R 1 ,R 2 ], . . . , (R i-1 , R i ], . . . (R 2-2 n , 255], wherein i is a positive integer and less than 2 n −2, corresponding ranges of a dot-matrix of bit-outputting are (0,Out 1 ), (Out 1 ,Out 2 ), . . . , (Out i-1 ,Out i ), . . . (Out 2-2 n ,11 . . . 1), the Out i being a binary representation of the n-bit depth, and a threshold M i of a central point of each of the gradations is sampled as a threshold comparison parameter for the gradation; 2) setting output probability thresholds with a n-bit imaging depth in the interval [0, 255]; 3) processing respectively the dots in the 2 n −1 gradations (R i-1 , R i ) based on an FM-AM mixed screening process using a dual-feedback error diffusion; and 4) computing dynamically output dot-matrix data, by using a dynamic gradation-changeable output mechanism with adjacent output gray levels in light of the probability thresholds F i and an accumulated value ShapeCur for controlling the shape of a current dot, when mixed screening in the gradations (R i-1 , R i ) is achieved.