There is provided with an image processing apparatus which performs transformation processing for an input image, and performs filter processing for a transformed image including the transformed input image in an image area, thereby generating an output image, comprising a determination unit configured to determine whether a pixel position to be mapped to a pixel of interest position in the transformed image by a transformation processing is present among pixel positions in the input image; and a calculation unit configured to set a pixel value, obtained by a convolution operation between filter coefficients and pixel values of pixels near a processing pixel position in the transformed image, as the pixel value of the pixel at the processing pixel position in the output image if the pixel position to be mapped is present.