Image differencing is an image processing technique used to determine changes between images. The difference between two images is calculated by finding the difference between each pixel in each image, and generating an image based on the result. For this technique to work, the two images must first be aligned so that corresponding points coincide, and their photometric values must be made compatible, either by careful calibration, or by post-processing (using color mapping). The complexity of the pre-processing needed before differencing varies with the type of image.
Image differencing techniques are commonly used in astronomy to locate objects that fluctuate in brightness or move against the star field.
The Hutchinson metric can be used to "measure of the discrepancy between two images for use in fractal image processing".
Famous quotes containing the word image:
“The image cannot be dispossessed of a primordial freshness, which idea can never claim. An idea is derivative and tamed. The image is in the natural or wild state, and it has to be discovered there, not put there, obeying its own law and none of ours. We think we can lay hold of image and take it captive, but the docile captive is not the real image but only the idea, which is the image with its character beaten out of it.”
—John Crowe Ransom (1888–1974)