Change the Color Temperature of Pictures in GIMP

GIMP is a free, open-source image editing software program with advanced tools that can change the color temperature of a picture. If your picture looks too warm or cool, you can easily change its color cast in GIMP. This can be done with the tools that come with GIMP, or by using a free color temperature plugin from the GIMP plugin registry.

Using Color Balance

Click "File" and "Open" within GIMP, then find and open the picture you'd like to edit. Click "Colors" and "Color Balance." Select the check boxes beside "Preview" and "Preserver Luminosity." Click "Shadows," then click and drag the sliders under "Adjust Color Levels." If your picture looks too cool, click and drag the sliders toward "Red," "Magenta" and "Yellow." If it looks too warm, click and drag the sliders toward "Cyan," "Green" and "Blue." Take care not to drag the sliders too much, as this will distort the color of your picture. Typically it takes only a very tiny movement of each slider to remove an undesired color cast. If you move the sliders too much, click the "Reset" button and start over again.

Using the Color Temperature Plugin

You can download the GIMP Color Temperature Plugin directly from the GIMP plugin registry. Copy and paste the plugin to the folder marked "Scripts" in the GIMP program directory. Open your picture in GIMP, then click "Filters," "Colors" and "Convert Color Temperature." Within the "Script-Fu" window, choose whether you'd like to obtain the original temperature from the slider or from the foreground color. Leave the slider beside "Original temperature" in its place. Click and drag the slider beside "Target temperature" to the right to make the picture cooler, and to the left to make it warmer. Move the slider beside "Intensity" to the right to make the picture lighter, and to the left to make it darker. Beside "Saturation change," click and drag the slider to the right to make the colors brighter, and to the left to make them dimmer. Click "Reset" at any time to set the sliders back to their default values.

If the tools in GIMP are too advanced for you, you may prefer to edit your photos in Picasa, Google's photo editor. While this editor doesn't give you quite as much control over your picture as GIMP, it's much easier and less confusing to use. It also has automatic fix buttons that let you fix the color and exposure of your pictures in one step.

Sources:

"Color Balance" GIMP.org