HOWTO: Round image corners in GIMP

1) Start GIMP and load an image file

2) Lower resolution to 500x500 if necessary:

Image -> Scale Image

3) Add transparency if necessary:

Layer -> Transparency -> Add alpha channel

4) Select -> All

5) Select -> Rounded Rectangle

6) Set corner radius between 10-20%, confirm with O.K.

7) Invert selection:

Select -> Invert (Inverse)

8) Cut corners in inverted selection:

Edit -> Cut (Ctrl+x OR Cmd+x)

9) Export image in PNG or JPG

http://www.tekstadventure.nl/branko/blog/2008/12/how-to-make-rounded-corners-with-the-gimp

HOWTO: Correct white balance

1) Launch “Layers” menu

2) Duplicate layer

3) Make all future modifications to duplicated layer

4) Adjust white balance automatically

Colors -> Auto -> White Balance

http://pareandfocus.com/index.htm/white-balance-with-gimp/