gdi + Graphics :: DrawImage真的很慢~~ [英] gdi+ Graphics::DrawImage really slow~~
问题描述
我正在使用GDI +图形在屏幕上绘制4000 * 3000的图像，但这确实很慢.大约需要300毫秒.我希望它只占用不到10毫秒的时间.
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",...);
//-------------------------------------------- //这部分大约需要300毫秒，太可怕了！
//-------------------------------------------- // this part takes about 300ms, terrible!
int width = bitmap->GetWidth();
int height = bitmap->GetHeight();
DrawImage(bitmap,0,0,width,height);
//------------------------------------------
//------------------------------------------
我不能使用CachedBitmap，因为我想稍后再编辑位图.
I cannot use CachedBitmap, because I want to edit the bitmap later.
我该如何改善?还是有什么问题吗?
How can I improve it? Or is any thing wrong?
此本地GDI功能还将图像绘制到屏幕中，仅需1毫秒:
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);
//--------------------------------------------- -----------------
//--------------------------------------------------------------
如果我想使用StretchDIBits，则需要传递BITMAPINFO，但是如何从Gdi +位图对象获取BITMAPINFO?我通过FreeImage lib进行了实验，我使用FreeImageplus对象调用StretchDIBits，它绘制得非常快.但是现在我需要绘制位图，并在位图的位数组上编写一些算法，如果有位图对象，如何获得BITMAPINFO?真的很烦-___________- |
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 -___________-|
推荐答案
您的屏幕分辨率为4000 x 3000?哇！
You have a screen of 4000 x 3000 resolution? Wow!
如果没有，您应该只绘制图像的可见部分，这样会更快...
If not, you should draw only the visible part of the image, it would be much faster...
[第一次评论后编辑]我的话确实有些愚蠢，我想DrawImage会遮盖/跳过不需要的像素.
My remark is indeed a bit stupid, I suppose DrawImage will mask/skip unneeded pixels.
编辑后(显示StretchDIBits)，我想速度差异的可能来源可能是 StretchDIBits 是硬件加速的("如果驱动程序不能支持JPEG或PNG文件图像"是提示...)，而DrawImage可能是(我没有证据！)用C编码，依赖于CPU的能力而不是GPU的能力.
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...
如果我没记错的话，DIB图像速度很快(尽管是与设备无关的").请参见高速Win32动画:"使用CreateDIBSection进行高速动画".好的，它适用于旧版Windows(1996年！)中的DIB与GDI.但是我认为这仍然是正确的.
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.
也许位图:: GetHBITMAP 函数可能会帮助您使用StretchDIBits(未经测试...).
Maybe Bitmap::GetHBITMAP function might help you to use StretchDIBits (not tested...).
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