1. A character recognition apparatus, comprising: a processor that executes instructions stored in a memory to perform the function of: a decolorization control section configured to carry out a decolorization processing for a sheet; an image reading control section configured to carry out an image reading processing for the sheet to which the decolorization processing is executed; and a character recognition processing section configured to carry out a character recognition processing for a decolorized image read through the image reading processing after the decolorization processing is carried out or for a generated image generated according to the decolorized image, the character recognition processing recognizes characters by collating the decolorized image with a characteristic data of characters stored in a storage, wherein the characters comprise text data; and an image synthesis section configured to assign a predetermined image to recognized characters according to a result of the character recognition processing, and synthesize the assigned predetermined image on a position where the recognized characters exist.