Thread: Making a moveable rectanlge on top of an image

  1. #1
    Registered User
    Join Date
    Oct 2006

    Making a moveable rectanlge on top of an image


    I am working on a small program where I need to be able to place rectangles on top of an image. The rectangles has to be able to be move and scaled using the mouse. What is the best way to do this?

    I was thinking of storing the coordinates of each rectangle, and every time the mouse is pressed inside the image I do a check against the coordinates to see if the mouse is inside one of the rectangles. And I would draw then using a brush on top of the image. But to me this does not sound like a very good way of doing this, so I am wondering if its a better way I could go about it?

    Im using c# if that helps in any way.


  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    It seems like a reasonable approach to begin with.
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  3. #3
    train spotter
    Join Date
    Aug 2001
    near a computer
    I usually do it some thing like..

    left button down is the trigger to start the rectangle (clear old). This is your start position. Draw a dot.

    check mouse move msgs to see if the left mouse is down, if it is get the current mouse position and expand the rectangle. Draw.

    check for left button up and draw the rectangle.

    How you do the drawing depends on the complexity of your background / drawing (speed needed to avoid flickering/shearing).

    Look at PtInRect()
    Beware of screen / client coordinates (and offsets from these to a control).
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