Help with simple applet - dragging box

Question

Hi I need help with a simple applet concept.
I have a picture drawn in the background, but I need to draw a square and resize it when I drag.
So with the picture in the background I click, drag the mouse, and it draws a rectangle from the starting point to where the mouse is while the mouse is clicked.
The only problem is I can't figure out how to do this without redrawing the whole picture. If I don't repaint, it just keeps stretching around rectangles and leaving them there.
I don't really need exact code, just an idea on how to do this without repainting the background every time the mouse is moved (because the picture in the background is complicated to draw and takes like a second).
Thanks
[nvm, found out about xormode]
Edited by: BugMenOTdhzj on Nov 30, 2009 4:47 PM

Answer 1

BugMenOTdhzj wrote:
..the picture in the background is complicated to draw and takes like a second).Paint the 'picture in the background' to a BufferedImage, then when it comes to paint()/paintComponent(), draw the BI to the Graphics object (clipped, if necessary (1)), then draw the rectangle to the Graphics object. This would be further optimised at time of rendering, by drawing both the 'picture in the background' BI and rectangle to a second BI, and finally writing that 2nd BI to the Graphics object.
1) There are potentially other improvements that can be made, particularly with clipping, but I suspect if you try as I suggested, the rendering will be very quick and responsive. I have 40 FPS sound trace animations that do a great deal more on each call to paintComponent(), before bursting the final BI to screen.