Re: [Gimp-user] Problem with exporting as .bmp for MS Windows BITMAP resource

[Richard <strata_ranger hotmail com>]

This is a known issue when exporting BMP files from within GIMP -- using RLE compression, colorspace or alpha 
channel in the target file is not supported by all BMP loaders, so check your Export options to be sure.


(This being said, I was unable to reproduce this scenario on my Win 10 system regardless of my export 
settings -- I have however encountered it in Windows XP.)


-- Stratadrake
strata_ranger hotmail com
--------------------
Numbers may not lie, but neither do they tell the whole truth.


________________________________
From: gimp-user-list <gimp-user-list-bounces gnome org> on behalf of BengtV <forums gimpusers com>
Sent: Wednesday, August 31, 2016 3:43 PM
To: gimp-user-list gnome org
Cc: notifications gimpusers com
Subject: [Gimp-user] Problem with exporting as .bmp for MS Windows BITMAP resource

I wanted to export an image as a .bmp file for use as a BITMAP resource in an MS
Windows .rc file.
The CBitmap method for loading the resource failed.
The road to making the file usable turned out *not* to be as straight as I had
hoped.

Looking at the header showed that the saved .bmp was compressed (type=3).
I converted the file using ImageMagick to the older "bmp3" format.
Now the file contained uncompressed (type=0) RGB data and loaded nicely into the
application.

Now the problem was the alpha channel.
Apparently, the ImageMagick team last year (on a request) added the possibility
to force
bmp3 to include the alpha channel with the --alpha flag.
Now the image looked strange in areas where there was a gradient in the alpha.
It seems like Windows wants the RGB data to be premultiplied with the alpha
channel.

So, after a long time searching through forums, I finally came up with an
ImageMagick
command line which converted a .png to a .bmp (bmp3) with premultiplied alpha.
Using this, my toolbar icons looked great, without any alpha-related border
artifacts.

My questions are:
1. Has anyone experienced the same problem?
   (Besides the guy requesting the --alpha flag from the ImageMagick team)  ;)

2. Why doesn't .bmp-export in GIMP have options to handle this?
   Is the image format used in any real extent on any other platform???
   (Like "export for Windows resource compatibility")

--
BengtV (via www.gimpusers.com/forums<http://www.gimpusers.com/forums>)
Forums - gimpusers.com<http://www.gimpusers.com/forums>
www.gimpusers.com
Forums. While there are many different GIMP forums of there, our own forums provide an extended way to 
communicate because they are connected to the official GIMP ...


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