Method for selecting image pixels to watermark and watermarking method using this selection

Method to select pixels that can be watermarked in an input image comprising the following steps:

• if necessary to represent the colours of the input image in a linear colour space, correct the input image by applying a predetermined gamma law,
• generate a ‘metameric’ image by replacing the colours of the input image pixels by colours that are metameric for the human eye,
• using simulation ‘reference’ sensor(s), simulate the capture of the input image and the capture of the metameric image by a camcorder having said simulation ‘reference’ sensors(s), in order to generate respectively a captured input image and a captured metameric image,
• determine, in a ‘measurement’ colour space and for each pixel of the input image, the distance between the colour of the corresponding pixel in the captured input image and the colour of the corresponding pixel in the captured metameric image, and
• select the pixels of the input image for which said distance is greater than a threshold value.