Rate-distortion Optimized Color Quantization for Compound Image Compression

In this paper, we present a new image compression scheme, which is specially designed for computer generated compound color images. First we classify the image content into two kinds: text/graphic content and picture content. Then a rate-distortion optimized color quantization algorithm is designed for text/graphic content, which introduces distortion to text content and minimizes the bit rate produced by the following lossless entropy compression algorithm. The picture content is compressed using conventional image algorithms like JPEG. The results show that the proposed scheme achieves better coding performance than other images compression algorithms such as JPEG2000 and DjVu.