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Reducing a large image

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enxio27
Forum Member

Reducing a large image

Post#1 by enxio27 » 26 Feb 2020, 01:25


When I reduce a large, black and white image (say, 1900x1600 to 190x160), I get a lot of gray edges. How do I avoid that? None of the color tools seem to have any effect in getting rid of the gray, including Color>Threshold.

Here's an example:
Snowflake black.xcf
(22.19 KiB) Downloaded 198 times
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rich2005
GIMP Guru

Post#2 by rich2005 » 26 Feb 2020, 09:40


Scale the large image (1900 x 1600) with interpolation NONE (or if that is too severe LINEAR)
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enxio27
Forum Member

Post#3 by enxio27 » 26 Feb 2020, 18:29


rich2005 wrote:
26 Feb 2020, 09:40
Scale the large image (1900 x 1600) with interpolation NONE (or if that is too severe LINEAR)
I tried both of them, but I'm still getting a lot of gray edges. Any ideas?
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rich2005
GIMP Guru

Post#4 by rich2005 » 26 Feb 2020, 19:29


Scaling using interpolation none should not produce any antialiasing. Can you post your large image somewhere?
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enxio27
Forum Member

Post#5 by enxio27 » 27 Feb 2020, 04:19


rich2005 wrote:
26 Feb 2020, 19:29
Scaling using interpolation none should not produce any antialiasing. Can you post your large image somewhere?
Here's the original:
Snowflake black.xcf
(301.67 KiB) Downloaded 217 times
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rich2005
GIMP Guru

Post#6 by rich2005 » 27 Feb 2020, 08:10


It could be that since your original image is not quite 1900x1600 scaling to 190x160 introduces some extra interpolation.

The attached 2 layers using Image -> Scale Image , using units percentage and size 10% , one layer interpolation NONE one layer interpolation LINEAR.
Attachments
Snowflake-none-lin.xcf
(42.11 KiB) Downloaded 136 times
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