To suppress jaggies occurring by expansion of image data included in printing information by carrying out correction of emphasizing of a contour of the image data and to prevent degrading of image quality by emphasizing a fuzzy contour.

This image forming system comprises an information processor 10 that forms printing information including image identification data indicative of whether or not an image is included in application data, size change identification data indicative of whether or not there is change of the size of the image data, change magnification data indicative of magnification for the change of the image data and image data, and an image forming apparatus 40 for performing a printing operation according to the printing information. The image forming system acquires the image identification data, the size change identification data and the change magnification data, respectively. When the acquired image identification data indicates that there is an image, the size change identification data indicates that there is the change of the size and the change magnification data is greater than threshold data as a reference of the necessity of the correction, the image forming system judges that the correction is necessary, and then the image forming system carries out the correction of emphasizing of the contour of the image data in the printing information.

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