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 Post subject: Binarize images
PostPosted: Sat Jun 28, 2025 9:47 am  (#1) 
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Hello everyone,
I need to have a clean B/W image starting from a photo taken in which some areas are overburnt and others are underexposed. Which G-MIC filter would you recommend? I tried dynamic range increase so far with good results, but I was wondering if there's anything better.
Thanks in advance
Jacopo


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 Post subject: Re: Binarize images
PostPosted: Sun Jun 29, 2025 8:10 am  (#2) 
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If you need to convert your image to true b/w (not grayscale), there is two built in ways in GIMP to do so. You can either go to the color menu and chose threshold (I did this straight with no enhancements; not really that great of result; could enhance before doing so to get better result):

Attachment:
threshhold.png
threshhold.png [ 31.13 KiB | Viewed 2545 times ]


Choose GEGL Color to Grey followed by dither and then threshold:

Attachment:
colortogreay_dither_threshold.png
colortogreay_dither_threshold.png [ 106.27 KiB | Viewed 2545 times ]


Did some enhancements then used GIMP's Newsprint:

colortogreay_dither_threshold


Attachments:
newsprint.png
newsprint.png [ 239.17 KiB | Viewed 2545 times ]

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 Post subject: Re: Binarize images
PostPosted: Sun Jun 29, 2025 8:12 am  (#3) 
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Now, if you are willing do use plugins outside of GIMP, you can give GMIC a whirl. there's several ways, but I'm only sharing dither. :)

Attachment:
G'MIC_dither.png
G'MIC_dither.png [ 167.71 KiB | Viewed 2545 times ]

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Lyle

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 Post subject: Re: Binarize images
PostPosted: Sun Jun 29, 2025 8:21 am  (#4) 
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OK; should have read your reply better. For G'MIC, again, way too many ways to enhance image prior to binaraizing if you will. Would recommend local variance normalization (under details) to give your image gritty contrast. You can then easily do dither afterwards for even stamp to get true binary b/w. :)

Attachment:
local Variance normalization.jpg
local Variance normalization.jpg [ 309.2 KiB | Viewed 2544 times ]


followed by dither:

Attachment:
local Variance normalization_dither.png
local Variance normalization_dither.png [ 204.54 KiB | Viewed 2544 times ]

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Lyle

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 Post subject: Re: Binarize images
PostPosted: Sun Jun 29, 2025 7:01 pm  (#5) 
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thanks!!


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 Post subject: Re: Binarize images
PostPosted: Mon Jun 30, 2025 2:21 pm  (#6) 
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Choose GEGL Color to Grey followed by dither and then threshold:

Excellent result!

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 Post subject: Re: Binarize images
PostPosted: Tue Jul 01, 2025 9:20 pm  (#7) 
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Rod wrote:
Choose GEGL Color to Grey followed by dither and then threshold:

Excellent result!

interesting indeed, maybe you or someone else can consider making a GEGL plugin that calls gegl:gray, gegl:dither, and gegl:threshold all in one with a few sliders and stuff. I'm not making this post to put pressure on anyone to develop GEGL I'm just pointing out what is possible


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