管理旋转移动栅格地图
我的应用程序呈现一个（光栅）移动地图。 我需要能够显示基于任何给定角度旋转的地图。 该程序当前使用 VC++/MFC，但问题是通用的。 我有一个源位图（CBitmap 或 HBITMAP），并使用 StretchBlt 将其绘制到设备上下文 (CDC)。 虽然对于angle=0（并且用户可以用鼠标平滑地抓取地图），这可以快速且平滑地工作，但如果我尝试旋转位图然后呈现它（使用 SetWorldTransform() 旋转位图），则情况并非如此大约需要数百毫秒，这太慢了）。
我认为解决方案是能够仅与当前屏幕上的像素相关，而不是旋转原始源位图 - 这是关键。
如果有人有类似实施的经验，那么它可能会节省我大量的试错工作。 谢谢！ 阿维。
My application present a (raster) moving map.
I need to be able to show the map rotated base on any given angle.
The program is currently in VC++/MFC but the problem is generic.
I have a source bitmap (CBitmap or HBITMAP) and draw it to the device context (CDC) using StretchBlt.
While this works fast and smooth for angle=0 (and the user can grab the map smoothly with the mouse), this is not the case if I try to rotate the bitmap and then present it (the rotation of the bitmap using SetWorldTransform() or so takes hundreds of miliseconds and this is too slow).
I think that the solution is to be able to relate only to the pixels that currently on the screen and not rotating the original source bitmap - and this is the key.
If someone has experience with similar implementation then it might save me lots of trial and error efforts.
Thanks!
Avi.
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看起来 SetWorldTransform 非常慢：
http://www.codeguru.com/Cpp/GM/ bitmap/specialeffects/article.php/c1743
虽然该文章中提供的其他选项速度更快，但当然还有其他更好的解决方案，如下所示：
http://www.codeguru.com/cpp/gm/gdi /article.php/c3693/ （也请检查评论中的修复和改进）
此外，这里还有一些非 Windows 中心的快速旋转算法：
http://www.ddj.com/windows/184416337?pgno=11
请注意，如果您保证 2 维的能力，您可以获得显着的速度提升。
It looks like SetWorldTransform is extremely slow:
http://www.codeguru.com/Cpp/G-M/bitmap/specialeffects/article.php/c1743
And while the other options presented in that article are faster, there are of course other better solutions like this:
http://www.codeguru.com/cpp/g-m/gdi/article.php/c3693/ (check the comments for fixes and improvements as well)
Also here are some non-Windows centric fast rotation algorithms:
http://www.ddj.com/windows/184416337?pgno=11
Note that if you guarantee power of 2 dimensions you can get significant speed improvements.
作为我的问题和提供的答案的后续，让我总结以下内容：
我使用了 http://www.codeguru.com/cpp/gm/gdi/article.php/c3693/。
它可以工作，并提供非常好的性能和流畅的显示。
其中存在一些错误，我需要修复并简化公式和
在某些情况下代码。
我将检查 http://www.ddj.com/ 中提到的算法windows/184416337?pgno=11 看看它是否提供了一些值得调整的突破性性能。
我的实现需要使用大型源位图，因此我需要修改代码，这样我就不会每次都旋转整个位图，而只会旋转将在屏幕上显示的相关部分（否则性能将无法接受）。< /p>
阿维。
As follow up to my question and provided answer, let me summarize the following:
I used the algorithm mentioned at http://www.codeguru.com/cpp/g-m/gdi/article.php/c3693/.
It works and provide pretty good performance and smooth display.
There were some bugs in it that I needed to fix as well as simplify the formulas and
code in some cases.
I will examine the algorithm mentioned at http://www.ddj.com/windows/184416337?pgno=11 to see if it provides some break through performance that worth adapting it.
My implementation required using a large source bitmap, so I needed to modify the code so I will not rotate the whole bitmap each time but only the relevant portion that will be displayed at the screen (otherwise performance would be unacceptable).
Avi.