Update: November 10, 2010 - minor bug fix to unselect after applying warming.
A couple of recent threads in the Gimp Users group on Flickr concerned how to warm or otherwise change the tone of an image. Since moving to The Gimp, I truly missed my warming filter, and didn't know how best to do this manually. This script takes some of the wonderful tips and suggestions and automates them.
Some of the script options are explained as follows
Wratten cooling and warming tones- simulates standardized cooling or warming photo lens filters using shades of blue or brown, respectively.
Roy's Warm uses color balance to adjust the magenta and yellow hues in the midtone range of the base image.
Brauer's Warm duplicates the layer and then colorizes the duplicate layer by adjusting the Hue.
Pasty Cadaveric Look This is not truly a cooling filter, as such, but does adjust flesh tones by creating an overlay layer from the red channel and filling it with white.
OVERLAY FILL METHOD
Fill Entire Layer Apply the Wratten filter by creating a new layer in overlay mode and bucket filling it with the chosen color.
Fill Red Channel Apply the Wratten filter by creating a new layer in overlay mode, but then using the red channel of the image to create a selection that is then filled with the chosen color. Good for changing skin tone without warming or cooling the entire image.
Jennifer at iffles.com has done a wonderful write-up documenting this script. Check it out at http://iffles.com/2010/06/05/gimp-script-showcase-warming-and-cooling-fi...
The filter will be in Colors->Warming or Cooling Filter