Just to take on a challenge, I decided to write an application to magnify only a particular section of the screen (under the mouse, following the mouse). The best way I can think to do this is to take a screenshot of the space under the form, enlarge, and paint on the form. I'm using this section of code to snap the picture inside a timer:
timer1.Stop();
//Reposition window
this.Left = Cursor.Position.X - this.Width / 2;
this.Top = Cursor.Position.Y - this.Height / 2;
//Bitmap to save image to
Bitmap bmpScreenshot = new Bitmap(this.Width, this.Height, PixelFormat.Format32bppArgb);
Graphics gfxScreenshot = Graphics.FromImage(bmpScreenshot);
//Grab section of screen shot
this.Opacity = 0.01;
gfxScreenshot.CopyFromScreen(this.Left, this.Top, 0, 0, this.Size, CopyPixelOperation.SourceCopy);
this.Opacity = 1;
//Save to class level so Paint can paint it
frame = bmpScreenshot;
//Make Double Buffered Panel repaint
dbPanel1.Invalidate();
timer1.Start();
In order to get the desktop (or whatever windows/contents are present) beneath the form, I set it's opacity to 0.01 (so that it's still clickable, which a click closes the app. Absolute 0 is not clickable) before taking the picture and then 1 after taking the snapshot... This creates a flicker. Is there a way I can get a bitmap of what's under the form without changing opacity or hiding/showing the form? I want a live image of what's under the form, not just a snapshot of when the app started.
I'm not looking for other apps that do this, I'm working on this so when I approach these problems I can learn a solution. I've tried changing the opacity (to all sorts of levels), using show and hide, SetVisibleCore(bool) on the window, but nothing lowers the flicker to an acceptable level. Any thoughts?
I would think you'd be better off displaying the magnified image offset from the cursor (look at the iPhone text selection/editing interface for example), and add some smart handling for the screen edges. That way you don't have to keep changing opacity, you just update the image and or placement of your form.