Patent ID: 6628427
Filing Date: 2003-09-30
Classification: G06T,H04N

Abstract:
A method for image processing, comprising the steps of:inputting n-step gray tone image data including a plurality of input pixels into an input image data buffer, each input pixel having an original value equal to one of n values representing n density levels, wherein n is a positive whole number; a first transforming step for transforming each of said input pixels stored in said input image data buffer into a transformed pixel having an output pixel value equal to one of m values representing m density levels, wherein m is a positive whole number and smaller than n, said first transforming step including the steps of: defining a pixel set including a plurality of non-processed pixels adjacent to each other in a processed-pixel recording buffer in accordance with a sum total of the original values of input pixels stored in said input image data buffer at locations corresponding to said plurality of non-processed pixels to be defined as a pixel set; and determining output pixel values from the m values in accordance with a sum total of the original values of input pixels stored in said input image data buffer at locations corresponding to a plurality of non-processed pixels of said pixel set defined by said defining step, each of said determined output pixel values being assigned to each non-processed pixel included in the pixel set defined by said defining step; a second transforming step for transforming each of said input pixels stored in said input image data buffer into a transformed pixel having an output pixel value equal to one of m values representing m density levels according to an error diffusion method; and selecting one of resultant values produced by said first and second transforming steps in accordance with an original value of an input pixel currently being processed and included in said input pixels stored in said input image data buffer.