Image processing apparatus and method setting thresholds of dither patterns based on density range and generating binary data depending on thresholds of target pixels

An image processing apparatus, comprising:

• an acquisition unit configured to acquire first multi-value data and second multi-value data based on input image data;
• a fractional data generation unit configured to generate first initial quantization data from the first multi-value data and first fraction data corresponding to fractions excluding the first initial quantization data from the first multi-value data, and generate second initial quantization data from the second multi-value data and second fraction data corresponding to fractions excluding the second initial quantization data from the second multi-value data;
• and
• a quantization data generation unit configured to generate first quantization data and second quantization data for printing dots by performing quantization processing using a dithering method on the first fraction data and the second fraction data;
• wherein
• a first dither pattern that is used for the first fraction data and a second dither pattern that is used for the second fraction data have same threshold values that are set for same pixels in a first gradation range, and have different threshold values that are set for same pixels in a second gradation range that exceeds the first gradation range;
• and
• the quantization data generation unit
• sets a first threshold value in the first dither pattern based on the first fraction data and the second fraction data, and generates the first quantization data based on whether or not the first fraction data is included in the first threshold value range, and based on the first initial quantization data;
• and
• sets a second threshold value in the second dither pattern based on the second fraction data and the first fraction data, and generates the second quantization data based on whether or not the second fraction data is included in the second threshold value, and based on the second initial quantization data.

A method for image processing, comprising

• an acquisition step of acquiring first multi-value data and second multi-value data based on input image data;
• and
• a generation step of generating first binary data and second binary data for printing dots by performing quantization processing using a dithering method on the first multi-value data and the second multi-value data;
• wherein
• a first dither pattern that is used for the first multi-value data and a second dither pattern that is used for the second multi-value data have same threshold values that are set for same pixels in a first gradation range, and have different threshold values that are set for same pixels in a second gradation range that exceeds the first gradation range;
• and
• in the generation step,
• a first threshold value for forming dots of the first dither pattern is set based on the first multi-value data and the second multi-value data, and the first binary data is generated according to whether or not threshold value corresponding to a target pixel of the first dither pattern is included in the first threshold value range, and
• a second threshold value for forming dots of the second dither pattern is set based on the second multi-value data and the first multi-value data, and the second binary data is generated according to whether or not threshold value corresponding to a target pixel of the second dither pattern is included in the second threshold value range.