Automatic pre-processing after image robustness analysis

The characteristic response curve of an imaging system is measured, to determine the system linearity. Images to be watermarked are analyzed to check if at least a prescribed target minimum of pixels is in the linear section of the imaging system response. When this criterion is met, the image data is left unchanged. However when it is not met, a tone correction is calculated and applied to the image. The automatic preprocessing of problem images increases their robustness and reduces the variance in robustness of a set of watermarked images.