Re: [Gimp-developer] gimp 2.8 prohibitively slow

On Wed, 2012-07-18 at 10:27 -0500, Aaron Paden wrote:
>  Even krita is a little better, which I thought 
> was surprising. It's able to at least load my largest image (8960x9088, 
> 7 MB) after awhile without halting and crippling my DE, 

Try increasing the tile size in your gimp preferences e.g. to two
gigabytes (and make sure you have at least three gigabytes of swap

8960x9088 is more like a 300 megabyte image in memory, if it's in RGB
mode - 4 bytes per pixel (R G B and Alpha), so
4 * 8960 * 9088
gives 325713920 bytes, and dividing that by (1024 * 1024) gives
310.625 megabytes.

A difference might be that MyPaint treats unpainted canvas areas
specially. Krita was from the start designed for professional use with
CMYK support, and hence targets images for print - your image isn't all
_that_ large in the PhotoShop / commercial print world - and so may
optimize large images more, I don't know.

To work with this image in gimp on a 32-bit system you will need:

(1) to have as large a tile cache size as you can -that's the amount of
memory gimp devotes to keepng the image in memory instead of on disk

(2) have the Undo History window in your dock, and use the button at the
bottom right to Discard Undo History roughly every 30 to 50 brush
strokes. Unfortunately I don't think you can bind that to a keyboard
shortcut, so you need the undo history window docked.

(3) save work frequently as xcf.gz - do not overwrite the same file each
time, in case you run out of memory while gimp is saving the file. Save
and Expert go much faster if you discard the undo history first.

(4) turn off thumbnails everywhere you can,
in edit/preferences/interface,
  turn off Enable Layer & Channel Perviews
in edit/preferences/Toolbox,
. turn off the "show active image"
in edit/preferences/Image Windows, you may want to
. turn off Show brush outline
this may make painting faster but unuseable, though.
. set pointer mode to rendering to crosshair only
. set pointer rendering to black and white

(5) make sure your gimp title bar shows the amount of memory in use - if
it doesn't, go to Edit/Preferences under Image Windows, Title and
Status; for Image Title format I have

%D*%f-%p.%i (%t, %L) %wx%h %m
(the default except for adding %m for memory)
and for Image status bar I have
%n (%m)
(the default)
That way if the status bar is saying something else, e.g. while you're
painting, you can still track memory usage easily.

(6) in edit/preferences/colour management,
. set Mode of operation to No color management
  (I just notice "colour" is misspelt there)

(7) do not use a theme with transparency. In Windows, use the classic
windows theme. In Linux, do not use compiz or a compositing window
manger (the ones that put drop shadows under windows), because these to
tend to reduce (sometimes halve) painting speed and increase memory

Hope this helps.


Liam Quin - XML Activity Lead, W3C,
Pictures from old books:
Ankh: freenode/#xml

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