Compression of color facial images using feature correction two-stage vector quantization

A feature correction two-stage vector quantization (FC2VQ) algorithm was previously developed to compress gray-scale photo identification (ID) pictures. This algorithm is extended to color images in this work. Three options are compared, which apply the FC2VQ algorithm in RGB, YCbCr, and Karhunen–Loeve transform (KLT) color spaces, respectively. The RGB-FC2VQ algorithm is found to yield better image quality than KLT-FC2VQ or YCbCr-FC2VQ at similar bit rates.With the RGB-FC2VQ algorithm, a 128 128 24-b color ID image (49 152 bytes) can be compressed down to about 500 bytes with satisfactory quality. When the codeword indices are further compressed losslessy using a first order Huffman coder, this size is further reduced to about 450 bytes.