Method and apparatus for processing image

An apparatus for processing an image, comprising;

• a dot discrimination portion for discriminating whether or not a target pixel to be processed belongs to a dot area;
• a character discrimination portion for discriminating whether or not the target pixel belongs to a character area;
• a contour discrimination portion for discriminating whether or not the target pixel belongs to a contour area;
• a fine line discrimination portion for discriminating whether or not the target pixel belongs to a fine line area;
• an inside and outside edge discrimination portion for discriminating whether the target pixel belongs to an inside edge or to an outside edge;
• a threshold value generating portion for selecting a threshold value from plural threshold values for error diffusion process in accordance with an area discriminated by at least one of the dot discrimination portion, the character discrimination portion, the contour discrimination portion, the fine line discrimination portion and the inside and outside edge discrimination portion to output the selected threshold value;
• and
• an error diffusion process portion for performing the error diffusion process for multilevel input data concerning the target pixel by utilizing the threshold value generated by the threshold value generating portion so as to produce output data whose gradation steps are reduced.

A method for processing an image, comprising the steps of:

• discriminating whether a target pixel to be processed belongs to an inside edge or to an outside edge;
• selecting a threshold value from plural threshold values for error diffusion process in accordance with a discrimination result so as to output the selected threshold value;
• and
• performing the error diffusion process for multilevel input data concerning the target pixel by utilizing the generated threshold value so as to produce output data whose gradation steps are reduced.