Image processing apparatus, method, and computer product low pass filtering correction coefficient for correcting image then subject to halftone processing

An image processing method for converting an input image into a halftone image to be output by a recording apparatus of an output apparatus, the image processing method comprising:

• determining a correction coefficient based on a characteristic of the recording apparatus with respect to each of a plurality of pixels in the input image;
• performing filter processing on the correction coefficient using a low-pass filter for reducing a high-frequency component depending on dither processing;
• correcting a pixel value of each of the plurality of pixels in the input image based on the correction coefficient on which the filter processing has been performed;
• and
• converting a corrected input image provided by the correcting into the halftone image by performing the dither processing.

A non-transitory computer-readable storage medium storing instructions that, when executed by a computer, cause the computer to perform a method for converting an input image into a halftone image to be output by a recording appartus of an output apparatus, the method comprising:

• determining a correction coefficient based on a characteristic of the recording apparatus with respect to each of a plurality of pixels in the input image;
• performing filter processing on the correction coefficient using a low-pass filter for reducing a high-frequency component depending on dither processing;
• correcting a pixel value of each of the plurality of pixels in the input image based on the correction coefficient on which the filter processing has been performed;
• and
• converting a corrected input image provided by the correcting into the halftone image by performing the dither processing.