Image forming apparatus

An image forming apparatus, comprising:

• a blocking unit configured (a) to generate first block property data having a first value that indicates that all pixels in a block image of a predetermined size obtained by dividing a color plane of an output image do not have a color of the color plane if all pixels in the block image do not have a color of the color plane, and (b) to generate first block property data having a second value that indicates that at least one pixel in the block image has a color of the color plane if at least one pixel in the block image has a color of the color plane;
• a gamma correction unit configured to perform gamma correction for the block image having the second value and not to perform gamma correction for the block image having the first value;
• a screen process unit configured to generate a block dot image by performing a screen process for the block image for which the gamma correction has been performed;
• and
• a toner adhesion amount calculating unit configured, in order to calculate a toner adhesion amount of an objective block image in a color plane, (a) to identify values of the first block property data of plural block images adjacent to the objective block image, and (b) to identify the toner adhesion amount of the object block as a value changed correspondingly to the identified values of the first block property data.