3. Performance

Methods for evaluating the quality of a compressed digital image include:

• objective methods, such as measurements :

  • the Peak Signal-to-Noise Ratio (PSNR), averaged over the entire image, but with no spatial correlation and therefore not an accurate reflection of the visual quality perceived (objectively) by the human visual system,

  • the root-mean-square error, MSE (Mean Squared Error ), or RSME (Root-Mean-Square Error ), translating the power of error between the source image and the decompressed image, also not always well related to visual quality,

  • Weighted MSE using psycho-visual masks,

  • the structural similarity index, or SSIM (Structural SIMilarity index ), which takes into account similarities between...