Patent ID: 8210633

Claim:
An image data processing apparatus for a liquid ejection apparatus which ejects a liquid related to image formation and a liquid related to preliminary ejection from a plurality of ejection openings towards a recording medium, the apparatus comprising: image data memory means for storing image data in which each pixel of a plurality of pixels disposed in a matrix has a density related to an image to be recorded on a recording medium; preliminary ejection data memory means for storing preliminary ejection data in which each pixel of the plurality of pixels has a density related to a preliminary ejection pattern to be formed on the recording medium through preliminary ejection; quantizing means for generating a quantized density for each one of target pixels in the plurality of pixels and for outputting a quantization error component occurring when generating the quantized density, the quantized density being generated by using one or more thresholds to quantize a density of each target pixel in the plurality of pixels into two or more values; and a subtracter for calculating a quantization error correction component for each one of target pixels in the plurality of pixels by subtracting a density of a target pixel contained in the preliminary ejection data from the quantization error component output from the quantizing means in relation to the target pixel; an allocator for allocating the quantization error correction component calculated by the subtracter to a plurality of the pixels positioned around the target pixel, wherein the quantizing means outputs the quantized density and the quantization error component of the target pixel by performing an addition using the density of the target pixel contained in the image data, the density of the target pixel contained in the preliminary ejection data, and an accumulated diffused error component assigned to the target pixel by the allocator when other pixels are quantized.