Working with Black-and-White and Color Images - GIMP 2.6 for Photographers: Image Editing with Open Source Software - page 335

4.4.3 Using the Curves Function to Color an
Image with One or More Colors
You should already be familiar with Curves (or gradation curves) as you used
this function in section 2.5.9 to edit the brightness, contrast, and color values
of the sample image. You can find this function by choosing Colors > Curves .
To colorize black-and-white photos with the Curves function, you must click
the Channel button to select a color channel. In contrast to the Levels function,
which is similar, the Curves function allows you to colorize an image with several
colors; the amount of colors available will depend on the quantity of points created
on the color curve as well as how these points were moved on the histogram curve.
Since you can reuse the settings for each color channel, you can use
one, two, three, or more colors to colorize images. This enables you to create
sophisticated image designs comparable to solarized color images.
You can also save the Curves settings and reload them for future use.
The Channel default setting is Value . This means the red , green and blue
color channels are edited at the same time when using the Value setting. In
the example image, I used the blue color channel to dye the image blue first.
Then more points were placed on the curve and, subsequently, moved
about in order to achieve a multicolor coloration of the image. You may repeat
this process for each color channel. Whether or not this will result in mixed
colors or a new color shade in the image depends on the shape of the curves.
Figure 4.30
The settings of the
color curve for the
blue channel