The technique I have used with GDI+ seems to be very flexible as it loads both file formats without any problems. I have attached a test piece that has a PNG toolbar and a JPG image that is shown in the help dialog box. I don't have all the support file finished but the code to do it is posted below.
mov hImage, rv(ResImageLoad,40) ; load an image from a resource, the trailing parameter is the resource ID.
.......
// The RC script entries
10 ICON "icon.ico"
20 RCDATA "toolbar.png"
30 BITMAP "gradient.bmp"
40 RCDATA "image.jpg"
; ========================================================
; the two macros that start and finish GDI+
GdiPlusBegin MACRO token
.data
gdii GdiplusStartupInput <>
GDItoken@@@@ dq ?
.code
mov gdii.GdiplusVersion, 1
mov gdii.DebugEventCallback, 0
mov gdii.SuppressBackgroundThread, 0
mov gdii.SuppressExternalCodecs, 0
invoke GdiplusStartup,ADDR GDItoken@@@@,ADDR gdii,0
ENDM
GdiPlusEnd MACRO token
invoke GdiplusShutdown,GDItoken@@@@ ; cleanup on exit
ENDM
; ========================================================
The procedure that does that work.
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ResImageLoad proc ResID:QWORD
LOCAL hRes :QWORD
LOCAL pRes :QWORD
LOCAL lRes :QWORD
LOCAL pbmp :QWORD
LOCAL hBmp :QWORD
LOCAL npng :QWORD
mov hRes, rv(FindResource,0,ResID,RT_RCDATA) ; find the resource
mov pRes, rv(LoadResource,0,hRes) ; load the resource
mov lRes, rv(SizeofResource,0,hRes) ; get its size
mrm npng, "@@@@.@@@" ; temp file name
invoke save_file,npng,pRes,lRes ; create the temp file
invoke GdipCreateBitmapFromFile,L(npng),ADDR pbmp ; create a GDI+ bitmap
invoke GdipCreateHBITMAPFromBitmap,pbmp,ADDR hBmp,0 ; create normal bitmap handle from it
invoke GdipDisposeImage,pbmp ; remove the GDI+ bitmap
invoke DeleteFile,npng ; delete the temp file
mov rax, hBmp ; return the bitmap handle in RAX
ret
ResImageLoad endp
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