Make conv of grays to different level of transp faster

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fmw42
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Re: Make conv of grays to different level of transp faster

Post by fmw42 »

try

convert image.png \( +clone -contrast-stretch 0 \) +matte -compose copy_opacity -composite result.png

+clone copies your image to use for the alpha channel
-contrast-stretch 0 will make your alpha channel graylevels become 0 to 255
-compose copy_opacity -composite will add the alpha channel to the image
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