GD portrait / landscape square thubmnails

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I'm trying to move (copy) a resize image (on a square fixed width/height image. (the resizing is done by PHP and GD)

This so all created thumbnails have the same size regarding if it's made from a landscape or portrait image. I do not want to crop the image!

The resized images are height 200 pixels or 200 pixels wide.
The square fixed image is 400 by 400 pixels.

Anyone here who might have a PHP code example how to do this?
I've used google, but till now I did not find anything usable.

Please note that I'm not after the resizing part.. All I need is the "move/copy" on the square part.

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Nevermind..

I found this great image processing solution.