IMAGE COMPRESSOR AND IMAGE EXPANDER

摘要

PROBLEM TO BE SOLVED: To enhance image quality of a magnified image in an image compander that reproduces a magnified image corresponding to an original image from a reduced image. SOLUTION: A reduced image generating section 15 generates reduced image data consisting of number of pixels less than that of original image data on the basis of the original image data stored in a memory 14 and stores the reduced image data to a recording medium RM. A discrete cosine transform DCT processing section 16 applies two dimensional discrete cosine transform to a pixel value of the reduced image data to obtain reduced DCT coefficient data. An extended inverse discrete cosine transform IDCT processing section 17 applies extended inverse discrete cosine transform to reduced DCT coefficient data to obtain magnified image data consisting of many number of pixels than that of the reduced image to obtain the magnified image data. A contrast coefficient calculation section 18 obtains a contrast coefficient con to correct the contrast of the magnified image data so as to close to the contrast of the original image data to the utmost and records it to the recording medium RM.