How to rotate Bitmap in windows GDI?

How wo开发者_如何学Pythonuld I go about rotating a Bitmap in Windows GDI,C++?

You can do it with GDI+ (#include <gdiplus.h>). The Graphics class has the RotateTransform method. That allows arbitrary rotations. Use Image::RotateFlip() if you only need to rotate by 90 degree increments, that's a lot more efficient.

Sounds like you have to use PlgBlt. Take your rectangle's 4 corners as 2D Points, rotate them, then call PlgBlt.

From MSDN Bitmap Rotation:

To copy a bitmap into a parallelogram; use the PlgBlt function, which performs a bit-block transfer from a rectangle in a source device context into a parallelogram in a destination device context. To rotate the bitmap, an application must provide the coordinates, in world units, to be used for the corners of the parallelogram.

Another possibility (beyond those already suggested) is to use SetWorldTransform(). This is different in that it is modal and applies to the DC as a whole, not just a single operation. If you want to rotate one bitmap rotated, but other things without rotation, it's probably not your best choice. If you want to draw a number of things rotated, or (especially) if you want to rotate everything you draw (at least into one DC) it can work quite nicely though.