1. An image processing apparatus comprising: an input unit that inputs printing information containing image data; and a conversion unit that, when a pixel value of a first pixel from among successive N pixels (N is an integer equal to or larger than 2) of the image data is zero, (i) examines sequentially the successive N pixels until a pixel amongst the successive N pixels is discovered to have a non-zero pixel value, (ii) sets the discovered pixel as a new first pixel and (iii) performs a conversion of the successive N pixels, starting from the new first pixel, using coefficient values calculated based on a magnitude of each of the successive N pixels.