It is an object of the present invention to provide an image transform apparatus and an image transform program which can reduce a computation load for transforming a luminance image to a brightness image. The present invention attains the object by performing wavelet resolution of the luminance image first to generate J pieces (J is an integer equal to two or more) of sub band images, transforming a luminance value of each pixel of the sub band images to a brightness impression value based on a predetermined relation between luminance and brightness impression, and then performing wavelet synthesis of K pieces (K is an integer equal to two or more; K≦J) of sub band images having been subjected to the transformation of the luminance values to the brightness impression values, to generate a brightness image.