IMAGE COMPRESSION DEVICE AND IMAGE DECOMPRESSION DEVICE

摘要

PROBLEM TO BE SOLVED: To improve compression efficiency and to suppress image deterioration by changing pixel value that belongs to a pixel included in a transparent area in image data based on area data and performing prescribed compression to changed image data. SOLUTION: An image compression device is provided with an image changing means 101 and a compression means 102. The means 101 performs an image conversion which changes the color value of pixels included in a transparent area that belongs to image data in accordance with area data and produces changed image data. The means 102 performs a prescribed compression to the changed image data and produces compressed image data. For compression performed by the means 102, it is possible to use reversible coding such as Huffman coding and arithmetic coding and non-reversible coding such as orthogonal transformation and subband coding in the same way as the case of an image compression device using a conventional technology.