EFFECTIVE IMAGE COMPRESSION USING BLOCK TRUNCATION TECHNIQUE

Block truncation coding (BTC) is a simple and fast lossy compression technique for digitized gray scale images. The key idea of BTC is to perform moment preserving (MP) quantization for blocks of pixels so that the quality of the image will remain acceptable and at the same time the demand for the storage space will decrease. It is a simple and fast algorithm which achieves constant bit rate of 2.0 bits per pixel. The method is suboptimal and divides the original images into small sub-images using a quantizer, taking more size and processing time. The aim is to adapt the sub images to reduce the number of gray. In block truncation coding an image is firstly segmented into n x n blocks of pixels. In the most cases the size is 4 x 4, but other sizes as 8 x 8 can also be used. Secondly, a two level output is chosen for every block and bitmap is also encoded using 1 bit for every pixel. This directly reduces the dimension without any resolution change.