A method for illumination-independent change detection in a pair of
original registered gray images based on blob extraction. Blobs are
extracted from the two original images and their negatives, using an
enhanced blob extraction algorithm based on connectivity analysis along
gray-levels. Blobs extracted from the first original and negative images
are compared with blobs extracted from the second original and negative
images to determine whether each blob has a corresponding blob, i.e.
whether it is a matched or unmatched blob. All unmatched blobs are tested
for significance as "blobs of change" using a fitness measure based on
either a ratio of saliency gradients, or a product of this ratio and a
gradient distribution measure. The disclosed method is exact, fast,
robust, illumination-insensitive, and has low time-complexity