问题
I've been using DirectShow.NET to interface with a webcam in C# and so far everything has been going smoothly. However, right now I'm working on trying to set up a method to "crop" an image (while it's still being displayed as a webcam preview).
Basically, I'm trying to show some kind of a mostly transparent image on top of the IVideoWindow object. Dealing with transparency in C#, however, has been pretty far from a cakewalk.
So, how can I layer an Image object on top of an IVideoWindow? Thanks!
回答1:
There are two approaches how to achieve this:
- to use a video transformation filter and deliver mixed video to the renderer (that is, picture + your overlay)
- or, use VMR's 'mixerbitmap` feature to overlay at presentation time
DirectShow.NET has a sample for the second mentioned above:
Samples\VMR9\BitMapMixer BitmapMixer is an example of how to draw things over a video using VMR9.
Another sample there:
Samples\Players\DxText A sample application showing how to superimpose text strings on a datastream. The stream is read from an avi file.
Also discussed many times on MSDN Forums.
来源：https://stackoverflow.com/questions/7699024/showing-a-semi-transparent-image-object-over-an-ivideowindow-in-c-sharp-using-di