Working with Black-and-White and Color Images - GIMP 2.6 for Photographers: Image Editing with Open Source Software - page 334

4.4.2 Using the Levels Function to Color an
Image

You already learned how to use the Levels tool (tonality correction) to
increase the contrast and color values of an image. And you know that this
function allows you to edit the color channels separately (sections 2.5.8
and 2.6.3). Similarly, the brightness and contrast can be edited in grayscale
images by selecting Value in the Channel drop-down menu (top left of the
Levels window). Moreover, on black-and-white photos, you can add (or
mix) optional colors by modifying a single color channel (i.e., blue) or by
editing all three channels (red, green, and blue) at once.
Start by selecting a color channel from the Channel drop-down menu
(top left) to edit
the color range. In
this exercise, you
will edit the blue
channel. Move the
mid-tones slider—
the middle triangle
on the grayscale
bar underneath
the histogram
curve—to select
the desired color.
If you want to use
a mixed color for
your image, select
a second color
channel and repeat
the process. This
process will colorize
all image areas
equally according
to their brightness.
Using the sliders
for shadows (the black triangle under the histogram curve) and for highlights
(white triangle), you can adjust the brightness and contrast of the image.
If you want to use the same option settings to colorize several images,
simply click the small arrow button, top right in the Levels dialog window. In
the menu that opens, , choose Export Settings to File to save your settings in a
folder. To apply the settings to other images, just click the arrow button again
and choose Import Settings from File .

Figure 4.29
The Levels options dialog. At top,
the options for saving settings