Patent ID: 7379618

Claim:
An image conversion method for performing a predetermined image conversion, which is one of image upsizing and image downsizing, on a first image to generate a second image, comprising: a first step of distinguishing a shadow portion in the first image; a second step of performing a first conversion process on the shadow portion using a brightness value of a pixel according to details of the predetermined image conversion; and a third step of performing a second conversion process on a portion other than the shadow portion using a surface normal parameter which represents a surface normal of a photograph subject according to the details of the predetermined image conversion, wherein the first step includes the steps of: calculating a surface normal parameter of the first image; correcting the calculated surface normal parameter on the assumption that a photograph subject has a smooth surface; calculating a brightness value from the corrected surface normal parameter according to a predetermined illumination equation; and calculating, for each pixel, a difference between the calculated brightness value and an actual brightness value, and recognizing a pixel in which the difference is greater than a predetermined value as being the shadow portion, wherein results of the processes performed at the second and third steps are used to generate the second image.