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Asked: 2026-05-10T19:50:55+00:00

I am using a GDI+ Graphic to draw a 4000*3000 image to screen, but

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I am using a GDI+ Graphic to draw a 4000*3000 image to screen, but it is really slow. It takes about 300ms. I wish it just occupy less than 10ms.

Bitmap *bitmap = Bitmap::FromFile('XXXX',...);

//——————————————– // this part takes about 300ms, terrible!

int width = bitmap->GetWidth(); int height = bitmap->GetHeight(); DrawImage(bitmap,0,0,width,height);

//——————————————

I cannot use CachedBitmap, because I want to edit the bitmap later.

How can I improve it? Or is any thing wrong?

This native GDI function also draws the image into the screen, and it just take 1 ms:

SetStretchBltMode(hDC, COLORONCOLOR);    StretchDIBits(hDC, rcDest.left, rcDest.top,          rcDest.right-rcDest.left, rcDest.bottom-rcDest.top,          0, 0, width, height,         BYTE* dib, dibinfo, DIB_RGB_COLORS, SRCCOPY);

//————————————————————–

If I want to use StretchDIBits, I need to pass BITMAPINFO, But how can I get BITMAPINFO from a Gdi+ Bitmap Object? I did the experiment by FreeImage lib, I call StretchDIBits using FreeImageplus object, it draw really fast. But now I need to draw Bitmap, and write some algorithm on Bitmap’s bits array, how can I get BITMAPINFO if I have an Bitmap object? It’s really annoying -___________-|

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1 Answer

  1. You have a screen of 4000 x 3000 resolution? Wow!

    If not, you should draw only the visible part of the image, it would be much faster…

    [EDIT after first comment] My remark is indeed a bit stupid, I suppose DrawImage will mask/skip unneeded pixels.

    After your edit (showing StretchDIBits), I guess a possible source of speed difference might come from the fact that StretchDIBits is hardware accelerated (‘If the driver cannot support the JPEG or PNG file image‘ is a hint…) while DrawImage might be (I have no proof for that!) coded in C, relying on CPU power instead of GPU’s one…

    If I recall correctly, DIB images are fast (despite being ‘device independent’). See High Speed Win32 Animation: ‘use CreateDIBSection to do high speed animation‘. OK, it applies to DIB vs. GDI, in old Windows version (1996!) but I think it is still true.

    [EDIT] Maybe Bitmap::GetHBITMAP function might help you to use StretchDIBits (not tested…).

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