1. An image processing apparatus that generates an output image by deforming an input image by coordinate transformation, comprising: a divisor calculation unit configured to calculate a minimum value and a maximum value of a divisor, used in division operation of coordinate transformation, based on coordinate information of a pixel constituting the input image; a coefficient calculation unit configured to, based on a relation between a divisor and an error in division operation, obtain a range of the divisor in a way that a result of the division operation becomes equal to or smaller than an allowable error, and calculate a normalization parameter by dividing a minimum value of the range by the minimum value of the divisor calculated by said divisor calculation unit; a parameter adjustment unit configured to calculate an adjustment parameter, used in the coordinate transformation, by multiplying an input parameter by the normalization parameter, and output the adjustment parameter; and an image deformation processing unit configured to perform transformation processing of the coordinate information using the adjustment parameter, and output a result of the transformation processing.