To reduce printing of a background image which does not provide a forgery suppression effect since a background portion is not deleted or does not become pale because of the influence of a copying mode during copying and an image hidden in the background image is not floated out.

A kind of an input document image is discriminated and based on the discriminated kind of the input document image, one of latent image patterns constituting a latent image portion of the background image and being held beforehand, is selected. Based on the discriminated kind of the input document image, one of background patterns constituting the background portion of the background image and being held beforehand is selected. The selected latent image pattern and background pattern are used to generate the background image, and the generated background image is composed with the input document image.

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