Detecting conflicts between multiple different encoded signals within imagery, using only a subset of available image data

This disclosure relates to advanced signal processing technology including steganographic embedding and digital watermarking. One combination disclosed in the description includes an image processing method. The method includes: obtaining an image comprising a plurality of color channels; for each color channel of the plurality of color channels, creating a grayscale version of the color channel and creating an inverted greyscale version of the color channel; analyzing the grayscale inverted version and the grayscale non-inverted version to locate image areas including an encoded signal, said analyzing yielding a plurality of image areas; generating one or more detectability measures corresponding to the encoded signal for each of the plurality of image areas; for each color channel selecting only one (1) image area as a validation point based on one or more generated detectability measures for that color channel; and generating information associated with a spatial location of each of the validation points in the image. Of course, other features and combinations are described as well.