Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
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A lock (
) or https:// means you've safely
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The images in the left-hand panels show: (a, top left) the image of a famous face, (b, top right) the image blurred, (c, bottom left) the image with the blurred image subtracted and (d, bottom right) the image with pixel noise added. The images on the right show landscapes of the corresponding images on the right. Pixel intensity is represented by height of the landscape, with color added (red is high and blue is low). From Morgan (2003) with permission.
