Looking for more efficient software zoom

Question

I am using a C#, Winforms application with the Aforge library to pull video from a USB camera and manipulate that video.

I am doing it by using the new frame event handler and posting that image into a picturebox. So far, it has worked well and done what I want.

However, I recently found out I need to add software zoom to the application. My solution was to increase the size of the overall image and then grab a section of the new, larger image, that fit the measurements I needed. This is done on every new frame.

     int imageTopY;
     int imageTopX;
     Rectangle rect;

     bitmap = new Bitmap(bitmap, new Size(bitmap.Width * zoomTrackBar.Value, 
                                          bitmap.Height * zoomTrackBar.Value));

     imageTopY = ((bitmap.Height - height) / 2);
     imageTopX = ((bitmap.Width - width) / 2);

     if (imageTopY != 0 && imageTopX != 0)
             rect = new Rectangle(imageTopX, imageTopY, width, height);
     else
             rect = new Rectangle(0, 0, width, height);

      bitmap = (Bitmap)bitmap.Clone(rect, bitmap.PixelFormat)

This also does what I need it to. HOWEVER, it is not at all efficient. When the zoome level hits 3, the video becomes exceptionally laggy. There is a latency of 1-2 seconds between the video feed and what is going on. I can get up and do a little dance, and by the time I sit down in my chair, the me in the video starts doing a little dance :-P

Any suggestions on a better way to achieve what I am trying to do? Maybe something more streamlined?

Answer 1

Instead of enlarging the overall image, cut out the section you wish you zoom in to and fill the window with that image. This way, you are always having a max image size of the video window and not enlarging the overall image beyond the window's constraints.