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 and performing a compression process using the predetermined number of units of the color components and a table for color image data, 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 while dividing the acquired block, and performing a compression process using the generated units of the one color component and a table for monochrome image data.