Provided are an image signal processor, an operating method of the image signal processor, and an application processor including the image signal processor. The image signal processor includes a downscaling circuit configured to generate a first image signal by downscaling an input image signal; an image processing engine configured to generate a second image signal by performing a plurality of image processing operations on the first image signal; a first upscaling circuit configured to generate a third image signal by upscaling the second image signal; a second upscaling circuit configured to generate a fourth image signal by upscaling the first image signal; a correction information generating circuit configured to generate an image information signal by extracting information on image quality loss of the third image signal from the input image signal and the fourth image signal; and a recomposition circuit configured to generate an output image signal by recomposing the third image signal and the image information signal.