问题
I have a Delphi 6 application that receives and processes an image stream from an external camera. I have the code on a background thread since it is CPU heavy and I don't want it interfering with with the user interface code that runs on the main thread. I want to update a rectangular area on a form or frame with the TBitmaps I create from the camera's JPEG frames that are received at a rate of 25 frames per second.
I want to know what method will give me the best performance and what Windows API calls or Delphi calls to use to do it. I would guess I should not use a TImage or TPicture or similar VCL component because they run on the main thread and I'm pretty sure trying to get anything done via a Synchronize() call is going to be inefficient and has the potential to slow down the threads involved. I would also want a technique that provides a smooth video display like double buffered controls do without any "striping" effects. Also, any tips on proper Canvas locking or device context management, etc. would be appreciated, especially tips on avoiding common mistakes in freeing resources.
Of course, a link to a good code sample that does what I need would be great.
回答1:
AFAIK TBitmap are thread-safe, if you work only on its canvas. Synchronize is needed if you send GDI messages and need to refresh the screen, but from my experiment, using TBitmap.Canvas is just a wrapper around thread-safe Windows API. If you process the bitmap with pixel arithmetics (using e.g. Scanline), one unique bitmap per thread, you can do it on background.
But I suspect using TBitmap is not the most efficient way. Give a try to http://graphics32.org or http://aggpas.org which are very fast way to work on bitmaps.
If you can, as imajoosy proposed, the best way to process your input stream is to use direct X streaming process abilities.
For thread-safe process, if each thread is about to consume 100% of its core (which is very likely for image process), it is generally assumed that you shall better create NumberOfCPU-1 threads for your processing. For instance, you could create a pool of threads, then let those consume the bitmaps from the input stream.
来源：https://stackoverflow.com/questions/8708312/how-to-perform-an-image-stream-preview-to-a-delphi-6-frame-or-form-from-a-backgr