Multiple opacities in an image

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adamrobbins2018
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Multiple opacities in an image

Post by adamrobbins2018 » 2018-09-26T09:37:14-07:00

I have a black-and-white image where want to add transparency.
I need multiple transparency levels according to the grey level of each pixel. If a pixel is close to black, it must be opaque (less transparent). If grey, medium transparent, and if white, almost 100% transparent.Is there a way to do this? Does a .png format even support such multiple transparencies?
Thanks for your help in advance.

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fmw42
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Re: Multiple opacities in an image

Post by fmw42 » 2018-09-26T09:53:57-07:00

Yes, PNG supports 8-bit transparency. The command should be

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convert image.png -alpha copy image.png
see
https://imagemagick.org/Usage/masking/#alpha_copy


If that does not work. Then in Unix

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convert image.png \( +clone \) -alpha off -compose copy_opacity -composite image.png
For Windows,

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convert image.png ( +clone ) -alpha off -compose copy_opacity -composite image.png
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http://www.imagemagick.org/discourse-se ... f=1&t=9620
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http://www.imagemagick.org/Usage/reference.html
http://www.imagemagick.org/Usage/
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