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AnswerRe: free memory when constructor throw exception Pin
«_Superman_»19-Jan-17 19:32
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Albert Holguin20-Jan-17 10:14
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QuestionSend data to POS Printer by USB Pin
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QuestionLight weight solution for distrubted memory map Pin
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QuestionGdiplus: DrawImage not working Pin
Member 162132314-Jan-17 3:28
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AnswerRe: Gdiplus: DrawImage not working Pin
leon de boer14-Jan-17 23:45
leon de boer14-Jan-17 23:45 
Can I first say you have no error checking at all in that code ... really bad programming practice

cairo_win32_surface_get_dc can fail and return NULL ... read the manual.
Why might there not be a win32 surface, well because you have to set a #define CAIRO_HAS_WIN32_SURFACE 1 in the cairo library .... again in the manual.

You code is totally reliant on srcHDC being valid ... Yet inexplicably you don't check it.

Secondly you probably want an alpha channel on the CIMage .. the create should be CreateEx
CImage image;
image.CreateEx(width, height, 32, BI_RGB, 0, 0);

Thirdly read TransparentBlt detail and if we do the Alpha channel it will then copy the source alpha onto the destination alpha ... is that Ok? If not you have to use AlphaBlend function.

Fourth check GDIPlus I seem to remember it had issues with Alpha channels.

Final comment is you seem to be making life difficult for yourself using 3 different systems for reasons that aren't clear. You are moving bitmap data around between systems for no real reason what you want can be done in any of the 3 systems and even natively on the Win32 API. You are even initializing the GDI plus system with a draw process ... like seriously please don't do it are you really hell bent on making the draw as slow as possible. Start the GDIPlus with the window or program and close it when done but not in a draw process ever.
In vino veritas

GeneralRe: Gdiplus: DrawImage not working Pin
Member 162132325-Jan-17 10:57
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Questionwhat?where? Pin
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QuestionDisable a Tab on CPropertySheet Pin
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QuestionVS2008 Debugger and CStrings - inconistent display Pin
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QuestionMultithreading question Pin
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