1. An image processing method for dividing image data into a plurality of blocks and compressing the blocks on a block basis comprising: sequentially selecting a block to be compressed from among the plurality of blocks and acquiring the selected block; determining whether the acquired block is color or monochrome; and when it is determined that the acquired block is color, generating a predetermined number of units of color components of a predetermined color format while a resolution of each of the units of the color components is reduced and performing a compression process using the predetermined number of units of the color components and a table for color image data, wherein the predetermined number of units represent all color components of the predetermined color format, and when it is determined that the acquired block is monochrome, generating a predetermined number of units of one color component of the predetermined color format by dividing the acquired block while a resolution of the units of the one color component is maintained, and performing a compression process using the generated units of the one color component and a table for monochrome image data, wherein no units of other components of the predetermined color format are generated.