Edge-Enhanced Image Coding for Low Bit Rates

Many current progressive wavelet-based image coders attempt to achieve the greatest reduction in mean squared error (MSE) with each bit sent. In so doing, they tend to send information on the lowest-frequency wavelet coefficients first. At very low bit rates, images compressed by these coders are therefore dominated by low frequency information and blotchy artifacts. These effects combine to hamper recognition of objects in the images. In this paper, we present a new progressive image coder which employs edge enhancement with the goal of improving the visual appearance and recognizability of compressed images at very low bit rates. Important edges in the original image are captured and transmitted as side information together with a traditional wavelet coder bit stream. The decoder combines the two complementary information sources in a manner which, for certain image classes, can yield highly recognizable images at very low bit rates.