Resize images in TImageList under Linux
lazarus / 39-Graphics

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Chronos · 2018-03-27 14:21

I put a code for resizing images inside TImageList into wiki here:
http://wiki.freepascal.org/TImageList#Resize_all_images_in_TImageList
It works under Windows but not under Linux. The question is how to
make it work under Linux GTK2. I didn't test it under Qt.

If PixelFormat of temporary bitmaps is set to pf24bit or pfDevice then
images are resized under Linux but transparency doesn't work for them.
I tried to set TransparentColor and other properites but without
desired effect. It seems that transparency is handled somehow
differently under Gtk2 widgedset. Or it may be just because under
linux 24-bit colors are used.

Test project is attached bellow.

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wp · 2018-03-27 14:45

This article is very misleading. Support for mutliple image sizes and
resizing has been built into trunk in a very elegant and transparent
way. Did you read http://wiki.freepascal.org/TImageList#Multiple-
resolution_TImageList_in_Lazarus_1.9_and_newer right above your text?

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Chronos · 2018-03-30 09:50

Yes, I noticed that and also that it is for Lazarus 1.9 which is not a
stable version and won't come in near future as a stable version. So
it isn't usable for me. Also I don't want to supply multiple icons for
multiple resolutions. I just want to resize my current icons. Resizing
TImageList images may not be needed just for High DPI scaling but for
other purpose.

So back to my question. How to do that in multi-platform way? It seems
that TImageList internals are pretty complicated. That it isn't just
one combined bitmap but it also depends heavily on the widgetset. The
main problem is that methods Add/Insert/InternalInsert don't work
correctly with a transparent image under gtk2. And I don't know how to
fix that.