An image processing apparatus is provided with an input of multivalued image data, converts the inputted multivalued image data into binary image data, generates color data based upon the binary image data resulting from the conversion, judges identity between the generated color data and color data of a plurality of different specific images, and outputs the binary image data resulting from the conversion if non-identity is judged. If identity is judged to exist, however, output of the binary image data resulting from the conversion is halted.