1. A method for measuring degradations of a digitized image introduced when coding the image, said method comprising the steps of: dividing the image into coding blocks using a coding grid, applying a coding processing on pixel data in each said block, making use of a block transform calculation and an inverse block transform calculation, determining the coding grid of the coded image, in order to find an image division into coding blocks, used when coding the image, shifting the coding grid with respect to the coded image, so as to define an image division into analysis blocks each covering a boundary between two adjacent coding blocks, applying the block transform calculation to pixel data in the coded image using the shifted coding grid to obtain transformed coefficients for each analysis block defined by the shifted coding grid, extracting coefficients that could be affected by a block effect resulting from coding of the image, from the transformed coefficients, applying the inverse block transform calculation to the extracted transformed coefficients to determine the pixel data for each analysis block, for each analysis block, estimating an indicator of the degradation due to block effects, using pixel data in the coded image and pixel data in each analysis block, obtained by the inverse transform calculation, and determining an image degradation measurement by summing the degradation indicators of each analysis block.