Image processing apparatus and method

An image processing method of processing multilevel image data including values of respective color components in an image processing apparatus, the method comprising the steps of:

• adding quantization errors to the respective values of the color components of a target pixel, wherein the quantization errors are obtained from pixels for which a quantization has been already completed;
• performing the quantization to determine output values of the respective color components of the target pixel based on a combination of the values of the respective color components to which the quantization errors are added;
• calculating quantization errors of the respective color components of the target pixel based on the output values of the respective color components and the values of the respective color components to which the quantization errors are added;
• determining distribution weights for the respective color components in accordance with a combination of the values of the respective color components of the target pixel;
• and
• distributing the calculated quantization errors of the respective color components of the target pixel to values of the respective color components neighboring pixels in accordance with the weights determined in the determining step,
• wherein the distribution weights for the respective color components are determined in the determining step to be the same value or different values to each other in accordance with a combination of the values of the respective color components of the target pixel, and
• wherein the determined distribution weights for the respective color components have the same value when the output value of the respective color components of the target pixel are equal to each other.

A non-transitory computer readable medium containing a program for processing multilevel image data including values of respective color components to be processed by a computer, said program causing the computer to execute the steps of:

• adding quantization errors to the respective values of the color components of a target pixel, wherein the quantization errors are obtained from pixels for which a quantization has been already completed;
• performing the quantization to determine output values of the respective color components of the target pixel based on a combination of the values of the respective color components to which the quantization errors are added;
• calculating quantization errors of the respective color components of the target pixel based on the output values of the respective color components and the values of the respective color components to which the quantization errors are added;
• determining distribution weights for the respective color components in accordance with a combination of the values of the respective color components of the target pixel;
• and
• distributing the calculated quantization errors of the respective color components of the target pixel to values of the respective color components neighboring pixels in accordance with the weights determined in the determining step,
• wherein the distribution weights for the respective color components are determined in the determining step to be the same value or different values to each other in accordance with a combination of the values of the respective color components of the target pixel, and
• wherein the determined distribution weights for the respective color components have the same value when the output value of the respective color components of the target pixel are equal to each other.