Patent ID: 8023152

Claim:
A processor implemented method for frequency-modulation screening using error diffusion based on dual-feedback, comprising: (1) carrying out an operation T of threshold comparison in view of a final input value g″(m, n) of a pixel of an original image by a processor, wherein a result of the operation is converted to a corresponding value b(m, n) that a printer is responsive to for generating a corresponding pixel of a halftone image; (2) comparing the value b(m, n) of the pixel with a input value g′(m, n) of the same pixel by the processor to obtain a difference between b(m, n) and g′(m, n), wherein the difference is an error value e(m, n), the input value g′(m, n) is used for the operation T of threshold comparison; (3) multiplying the error value e(m, n) by preset weight distribution coefficients of an error diffusion filter e and then diffusing a result to unprocessed pixels around a current pixel by the processor, wherein a diffused error value to a pixel is weightedly added to a value g(m, n) of the pixel of the original image to obtain a new input value g′(m, n) of the pixel of the original image; (4) diffusing processed results to surrounding corresponding unprocessed pixels, and weightedly adding each of the diffused results and each of parameters of error diffusion in the steps (2) and (3) to the input value g(m, n) of the pixel of the original image by the processor to obtain the final input value g″(m, n) of the pixel, wherein the processed results are obtained by implementing a multiplying operation in view of the output value b(m, n) of the current processed pixel using a diffusion filter w which has been processed with a dithering algorithm, and the step (4) is a parallel operation of the steps (2) and (3); (5) repeating the steps (1)-(4) until the input values g(m, n) of all pixels are processed.