Resizing an image in Gimp is very slow.

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Resizing an image in Gimp is very slow.

Alussam
I often have an image size of up to 5000 x 4000 px and maybe 50 or more undo
history. There is often 10 - 15 layers, but I have then flattened the whole lot.
When I go to resize it (to 1800 x 1200 px) Gimp is VERY slow.  The progress bar
will move quickly to ,say, 2/3 of the way, then stop for sometimes up to 3 or 4
minutes. I have 10.4 Gimp. I have tried deleting the undo history, but with no
difference. If I have a saved XCF file, I have tried closing my image, then
reloading it. When Gimp is stalled, it uses high CPU but not disc.  Then the
resizing process is fast. Have you any idea why this happens & how to solve it?

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Re: Resizing an image in Gimp is very slow.

Shlomi Fish
Hi CharlesJ-J,

On Mon, 10 Feb 2020 21:56:34 +0100
CharlesJ-J <[hidden email]> wrote:

> I often have an image size of up to 5000 x 4000 px and maybe 50 or more undo
> history. There is often 10 - 15 layers, but I have then flattened the whole
> lot. When I go to resize it (to 1800 x 1200 px) Gimp is VERY slow.  The
> progress bar will move quickly to ,say, 2/3 of the way, then stop for
> sometimes up to 3 or 4 minutes. I have 10.4 Gimp. I have tried deleting the
> undo history, but with no difference. If I have a saved XCF file, I have
> tried closing my image, then reloading it. When Gimp is stalled, it uses high
> CPU but not disc.  Then the resizing process is fast. Have you any idea why
> this happens & how to solve it?
>

This works fine for me with gimp-2.10.14 on mageia linux v8 on a sandy bridge
core i3 box. What are your system specs? And can you share a problematic
sample image? See https://github.com/shlomif/writing-the-perfect-question .

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Shlomi Fish       https://www.shlomifish.org/
https://www.shlomifish.org/open-source/projects/fortune-mod/

With the NSA’s budget you would expect evil to be extinct by now. (By Kika).
    — http://www.shlomifish.org/humour/bits/facts/NSA/

Please reply to list if it's a mailing list post - http://shlom.in/reply .
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Re: Resizing an image in Gimp is very slow.

Liam R E Quin
In reply to this post by Alussam
On Mon, 2020-02-10 at 21:56 +0100, CharlesJ-J wrote:
> I often have an image size of up to 5000 x 4000 px and maybe 50 or
> more undo
> history.


Notice the memory usage in the title bar and/or status bar. When GIMP
is using all of your memory, everything will be very very slow.

(1) Make sure the "tile cache size" is set to at least half of your
physical RAM in Edit->Preferences. You may need to experiment as you
didn't mention operating system or how much memry you have or whether
32 or 64 bit.

(2) there were some speedups - get 2.10.14, not 10.4, and see if that
helps?

i routinely work with large images but not with 35 layers. Sometimes
40,000 pixels on a side.

slave liam



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