Block truncation coding (BTC) is a lossy moment preserving quantizatio
n method for compressing digital gray-level images. Its advantages are
simplicity, fault tolerance, the relatively high compression efficien
cy and good image quality of the decoded image. Several improvements o
f the basic method have been recently proposed in the literature. In t
his survey we will study the basic algorithm and its improvements by d
ividing it into three separate tasks; performing quantization, coding
the quantization data and coding the bit plane. Each phase of the algo
rithm will be analyzed separately. On the basis of the analysis, a com
bined BTC algorithm will be proposed and the comparisons to the standa
rd JPEG algorithm will be made.