Patent ID: 8351083

Claim:
An image processing apparatus comprising: an input section, configured to input image data of a pixel of interest; an adder, configured to add diffusion data diffused from errors occurred by decrease of a tonal number of image data to the image data of the pixel of interest; a converter, configured to decrease the tonal number of the image data of the pixel of interest, to which the diffusion data has been added, using an error diffusion method or minimized average error method; and a diffuser, configured to diffuse an error occurred in the decrease of the tonal number for the pixel of interest to pixels close to the pixel of interest, wherein the apparatus further comprising: a calculator, configured to integrate, per a pixel, the errors occurred by the decrease of the tonal number of the image data in a predetermined image region as a total amount of the errors, wherein the predetermined image region is larger than an area including the pixels to which the error is diffused by the diffuser; and a threshold setting section, configured to set a threshold value used in the error diffusion method or minimized average error method based on the image data of the pixel of interest and the total amount so that the threshold value becomes small when the total amount becomes large, and the threshold value becomes large when the total amount becomes small.