PURPOSE: To make it possible to form a dynamic fault image at a sufficient speed without special purpose hardware by matching a composite image formed from a first image to a second image at every pixel.

CONSTITUTION: A first, a second and a composite images each have pixels capable of being displayed by one set of apparatuses so that each pixel is defined at display coordinate position and strength value. A matrix having a floating point value is calculated so that the coordinate position of the first image can be mapped to that of the composite image, and converted to a fixed point value display. Then, the corresponding coordinate position of the first image is calculated by the fixed point calculation for the displayed coordinate position of the composite image, the pixel strength value to the coordinate position of the composite image is extrapolated from the strength value of the pixel surrounding the corresponding position of the first image, and one set of pixels for forming the composite image is generated. Thus, the composite image has the deformation of the first image of the feature matched to that of the second image, and the pixel is matched to the coordinate position of the pixel of the second image.