Patent ID: 7397972

Claim:
An image transform method, for transforming original input image data into image data expanded by a ratio represented by a rational number or an integer, comprising the steps of: reducing correlation in the vertical and horizontal directions of an image that is linearly expanded in the vertical and horizontal directions to generate first expanded image data by a rank order processing in a window having a predetermined size wherein a target pixel and its neighboring pixels in the linearly expanded image data are included; performing linear interpolation, based on correlation with a target pixel constituting said original image data and neighboring pixels arranged in oblique directions, using said neighboring pixels to generate second expanded image data by determining an interpolation direction, wherein the neighboring pixels comprise a first neighboring pixel and a second neighboring pixel, and wherein determining an interpolation direction comprises: calculating a left oblique difference using the target pixel and the first neighboring pixel; calculating a right oblique difference using the target pixel and the second neighboring pixel; determining the left oblique direction to be the interpolation direction when the left oblique difference is smaller than a threshold value and when the right oblique difference is greater than a threshold value; and determining the right oblique direction to be the interpolation direction when the left oblique difference is greater than a threshold value and when the right oblique difference is smaller than a threshold value; and employing said first expanded image data and said second expanded image data in an arithmetic combination to generate a final image.