pextrem(1) find minimum and maximum values in RADIANCE picture


pextrem [ -o ] [ picture ]


Pextrem locates the minimum and maximum values for the input picture, and prints their pixel locations and color values. The first line printed contains the x and y pixel location (x measured from the left margin, y measured from the bottom), followed by the red, green and blue values. The second line printed contains the same information for the maximum value.

The -o option prints the original (radiance) values, undoing any exposure or color correction done on the picture.

If no input picture is given, the standard input is read.


Greg Ward


The luminance value is used for comparison of pixels, although in certain anomolous cases (ie. highly saturated colors) it is possible that pextrem will not pick the absolute minimum or maximum luminance value. This is because a fast integer-space comparison is used. A more reliable floating-point comparison would be slower by an order of magnitude.