A processing apparatus which decompresses compressed data and outputs the decompressed data to a processing unit configured to perform conversion processing of converting the decompressed data into data for printing; the apparatus comprises: an input unit configured to input the compressed data; a calculation unit configured to perform calculation for decompressing the compressed data input by the input unit; and a correction unit configured to correct data generated by the calculation unit such that a value of the data becomes a specific value handled by the processing unit.

A history generating apparatus includes an image generating section, an image reading section and a history generating section. The image generating section generates a bitmap first image and generates initial attribute information indicating attributes of respective pixels of the first image. The image reading section reads an image based on the first image formed on paper so as to generate a bitmap second image. The history generating section separates the second image into image regions by attribute indicated by the initial attribute information, performs image processing on each of the image regions according to the attribute and combines the image regions so as to generate a history image.