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Hello,
I would like to use Gimp to prepare files for riso printing and for this I need to convert each individual color layer from opacity (x%) to greyscale ((100-x)% luminosity).
Precisely, this is the conversion I need:
- [color] at 100% opacity -> black
- [color] at 75% opacity -> grey (25% luminosity)
- [color] at 50% opacity -> grey (50% luminosity)
- [color] at 31 % opacity -> grey (69% luminosity)
etc.
And [color] can be replaced by any existing color. I have one layer per color.
Would you know how to do this? In Photoshop, there is a shortcut to do this at seen here: https://youtu.be/UrFq5KliP04?t=263
This is exactly what I would like to reproduce.
Thanks in advance for your help.
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08-06-2023, 10:40 PM
(This post was last modified: 08-06-2023, 10:40 PM by Ofnuts.)
(08-06-2023, 08:46 PM)Purple_ghoost Wrote: Hello,
I would like to use Gimp to prepare files for riso printing and for this I need to convert each individual color layer from opacity (x%) to greyscale ((100-x)% luminosity).
Precisely, this is the conversion I need:
- [color] at 100% opacity -> black
- [color] at 75% opacity -> grey (25% luminosity)
- [color] at 50% opacity -> grey (50% luminosity)
- [color] at 31 % opacity -> grey (69% luminosity)
etc.
And [color] can be replaced by any existing color. I have one layer per color.
Would you know how to do this? In Photoshop, there is a shortcut to do this at seen here: https://youtu.be/UrFq5KliP04?t=263
This is exactly what I would like to reproduce.
Thanks in advance for your help.
Already answered on GDSE. 
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08-07-2023, 06:36 PM
(This post was last modified: 08-07-2023, 06:43 PM by Purple_ghoost.)
(08-06-2023, 10:40 PM)Ofnuts Wrote: (08-06-2023, 08:46 PM)Purple_ghoost Wrote: question
Already answered on GDSE.
Thank you for your answer.
However, I am confused as opacity in Gimp does not correspond to what I expected.
In Photoshop, when you change "opacity", it does not change the tint whereas in Gimp, the tint changes.
Here is an example: hslpicker.com/#005ed1,0.69/#fff
The color I used is RGB(0, 94, 209) or TSL(59, 100, 41). When used in Photoshop with an opacity set to 69% on a white background, the result I get is RGB (79, 144, 223) or TSL(59, 69, 59) as in the hlspicker example above. In Gimp, I get RGB (151, 167, 225) or TSL(63, 55, 74).
What did I get wrong?
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(08-07-2023, 06:36 PM)Purple_ghoost Wrote: (08-06-2023, 10:40 PM)Ofnuts Wrote: (08-06-2023, 08:46 PM)Purple_ghoost Wrote: question
Already answered on GDSE.
Thank you for your answer.
However, I am confused as opacity in Gimp does not correspond to what I expected.
In Photoshop, when you change "opacity", it does not change the tint whereas in Gimp, the tint changes.
Here is an example: hslpicker.com/#005ed1,0.69/#fff
The color I used is RGB(0, 94, 209) or TSL(59, 100, 41). When used in Photoshop with an opacity set to 69% on a white background, the result I get is RGB (79, 144, 223) or TSL(59, 69, 59) as in the hlspicker example above. In Gimp, I get RGB (151, 167, 225) or TSL(63, 55, 74).
What did I get wrong?
New comment on GDSE. Actually a "default" v.s "legacy" blend mode quirk (see screenshot on GDSE).
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