Image Compression Techniques

Image compression is minimizing the size in bytes of a graphics file without degrading the quality of the image to an unacceptable level. The reduction in file size allows more images to be stored in a given amount of disk or memory space. It also reduces the time required for images to be sent over the Internet or downloaded from Web pages.

Loosy compression

1. An approximate reconstruction of original data. The loosy compression that produces the imperceptible difference can sc called visually lossless.
2. There is some Loss of information
3. Used at low bit rates introduce compression artifacts.
4. Higher compression ratio is achieved with the loosy compression. This is achieved at cost of losing out finer details of an image.
5. Image & music too need not be reproduced exactly an approximation of original image is enough for most purposes.
6. Loosy method are suitable for natural  images such as photos in applications when minor loss of fidelity is acceptable to achieve a required image.

Lossless compression

1. This is the exact replica of an original image.
2. There is no loss of quantitative information
3.  It require higher bit rate for transmission.
4. Compression ratio is low. Compression ratio defined as ratio of size of uncompressed image to size of compressed file.
5. Used for archival purpose &often medical imaging, technical drawings, clip art or comics.
6. Text compression, text document &binary executable must be compressed in this technique. They need to be exactly reproduced.