1. An image processing apparatus capable of converting input image data into image data expressing a dot pattern cell by cell, the image processing apparatus comprising: a detection unit configured to detect a pixel having a specific pixel value in the input image data; and a determination unit configured to determine an output value of a pixel included in each cell by arranging as many print pixels as a number of print pixels according to a total value of pixel values of a pixel group including pixels included in a cell except the pixel detected by the detection unit on any of the pixels in the pixel group cell by cell.