Region of interest in JPEG

This paper describes three methods to encode a region of interest (ROI) of arbitrary shape in the JPEG standard. The ROI is part of the image encoded with higher quality than the rest of the image. Two of the described methods are based on thresholding of DCT coefficients. The last method is based on the early termination of the entropy coding phase. All methods are fully compatible with existing JPEG decoders. Using ROI, it is possible to reduce the bitrate to only a fraction of the original value. The results in this paper show that thresholding of original DCT coefficients provides superior performance in terms of the PSNR-B index