说明：  Applications of Computer graphics, especially digital photographs and other complex color images,can produce very large file sizes. Problems of storage space and the necessity to fast transmit image data across networks and over the Internet, have thus, led to the growth of a range of image compression techniques, to minimize the physical size of files. Majority of the compression approaches are not dependent of particular file formats, several formats support a number of different compression kinds. They are an important segment of digital image formation, utilization and storage. But, a number of aspects such as efficiency, compression ratio etc., must be taken into account when using compression algorithms