How to make a resizeable rectangle selection tool?

Question

I'm trying to write a very simple photo editor using C# 2008 or QT4.

How to make a resizeable rectangle selection tool like the photoshop did?

Answer 1

If you are talking about the "classic" "rubber band" type of selection rectangle, check out How to draw a rubber band rectangle or a focus rectangle in Visual C#.

Answer 2

WPF Code Example: http://www.codeproject.com/KB/WPF/wpfmarchingants.aspx?display=Print

This one is a bit more complicated because it involves image cropping, but if you scroll down to the selection rectangle, you can see the basic formulas for calculating the rectangle: http://69.10.233.10/KB/WPF/ImageCropper.aspx

Lastly, another one using GDI: http://codelog.blogial.com/2008/10/31/rubber-band-selection-rectangle-in-c/

If you provide more specifics, I'm sure we can help you out more.