Effect of image activity on lossy and lossless coding performance

Summary form only given. When we compress a variety of multimedia images using a fixed wavelet filter, the PSNR values vary widely. Similarly in lossless image compression using a fixed integer wavelet transform, the bit rates can vary sharply. These large variations can be attributed to the image activity measure (IAM). We define and use a number of IAM from image variance, edges, wavelet coefficients and gradients, and analyse various images to see the effect of such image activity on the coding performance. It is observed that for both textures and images, a gradient-based activity measure is found to be the most effective measure in capturing the activities and solely determines the compressibility of an image