ppmdim

Dim PPM image by brightness factor

TLDR

Dim image

$ ppmdim [factor] [input.ppm] > [output.ppm]

Dim by 50%

$ ppmdim 0.5 [input.ppm] > [output.ppm]

Dim by 25%

$ ppmdim 0.25 [input.ppm] > [output.ppm]

ppmdim reduces the brightness of a PPM image by multiplying each pixel value by the specified factor. A factor of 1.0 leaves the image unchanged, while 0.0 produces a completely black image. Reads from stdin if no file is specified.This is the complement of ppmflash, which brightens toward white. Both tools are useful for creating fade-to-black or fade-to-white animation effects when applied with varying factors across a sequence of frames. Part of the Netpbm toolkit.This program is largely superseded by pamfunc (with the -multiplier option), which is more general. ppmdim remains available for backward compatibility and may be faster due to its use of integer arithmetic.