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ppmtopgm - convert a PPM image to a PGM image |
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ppmtopgm [ppmfile] |
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This program is part of Netpbm(1). ppmtopgm reads a PPM as input and produces a PGM as output. The output is a ’black and white’ rendering of the original image, as in a black and white photograph. The quantization formula ppmtopgm uses is g = .299 r + .587 g + .114 b. Note that although there is a pgmtoppm program, it is not necessary for simple conversions from pgm to ppm , because any ppm program can read pgm (and pbm ) files automatically. pgmtoppm is for colorizing a pgm file. Also, see ppmtorgb3 for a different way of converting color to gray. And ppmdist generates a grayscale image from a color image, but in a way that makes it easy to differentiate the original colors, not necessarily a way that looks like a black and white photograph. |
Cold-hearted orb that rules the night Removes the colors from our sight Red is gray, and yellow white But we decide which is right And which is a quantization error. |
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pgmtoppm(1), ppmtorgb3(1), rgb3toppm(1), ppmdist(1), ppm(1), pgm(1) |
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Copyright (C) 1989 by Jef Poskanzer. |