An image processing apparatus performs image processing to print a color materials of a first color and a second color. When a sum of a first gradation data for the first color and a second gradation data for the second color is equal to or smaller than the maximum value of thresholds of a first threshold matrix, a generation unit generates a second quantization data for the second color based on a result of comparing the second gradation data with a second threshold. When the sum is greater than the maximum value, the generation unit generates third gradation data by subtracting the maximum value from the sum and generates the second quantization data based on a result of comparing the third gradation data with the first threshold or a result of comparing a difference between the second gradation data and the third gradation data with the second threshold.