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BMP 32-bit alpha files not compatible with win32 LoadImage()

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This code works fine with files created by Paint.Net 4.0.x and the old BMPX export DLL (BMP32 Paint.NET FileType.dll):


if (m_hbm == NULL)
	DWORD derr = GetLastError();
	Logger("toolbar LoadImage error = %d  %u  %x", derr, derr, derr);
m_ilToolBar = ImageList_Create(bmpw, bmph, ILC_COLOR32, 11, 4);
ok2 = ImageList_Add(m_ilToolBar, m_hbm, NULL);


If I use 4.3.12 with the same PDN file and save as 32-bit BMP, the ::LoadImage fails with GetLastError() == 183:  11:58:24.266 - toolbar LoadImage error = 183  183  b7


If I look at the old DLL export and the new built-in export, I see that the new version uses a larger header.  I can provide samples of both if needed.


Our use case is creating bitmaps with transparency for Windows UI elements like toolbar buttons.  The old Win32 API calls won't read PNG.

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In Paint.NET v4.2, many formats (including BMP) were switched over to the newer WIC encoders/decoders.


You may need to start using WIC in your application, or re-encode your bitmap files with a different program.

(September 25th, 2023)  Sorry about any broken images in my posts. I am aware of the issue.

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Thanks, that makes sense to avoid maintaining a bunch of codecs when Microsoft has done that for you, but it's a shame that for 32-bit with alpha the results aren't compatible with their own Win32 API call.




It looks like it might be possible to get a HBITMAP from a WIC bitmap, though for now it's easier for us to keep using the old BMPX export DLL.

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