23 lines
548 B
Text
23 lines
548 B
Text
# Convert color image (PPM) to greyscale image (PGM)
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(de ppm->pgm (Ppm)
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(mapcar
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'((Y)
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(mapcar
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'((C)
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(/
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(+
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(* (car C) 2126) # Red
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(* (cadr C) 7152) # Green
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(* (caddr C) 722) ) # Blue
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10000 ) )
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Y ) )
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Ppm ) )
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# Convert greyscale image (PGM) to color image (PPM)
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(de pgm->ppm (Pgm)
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(mapcar
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'((Y)
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(mapcar
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'((G) (list G G G))
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Y ) )
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Pgm ) )
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