6. An objective measure for evaluating the performance of pixel level fusion methods is introduced. The proposed measure employs mutual information and conditional mutual information in order to assess and represent the amount of information transferred from the source images to the final fused greyscale image. Accordingly, the common information contained in the source images is considered only once in the formation of the final image. The measure can be used regardless the number of source images or the assumptions about the intensity values and there is no need for an ideal or test image. The experimental results clarify the usefulness of the proposed measure.

A measure for assessing the perceived information in false color images is developed. The measure employs the uniform L*a*b* color space and the K-L divergence to represent the amount of information that the observer can distinguish.