User Guide

GNU Image Manipulation Program
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Figure 8.14: Example for layer mode ‘Dodge’
(a) Mask 1 is used as upper layer with 100% opac-
ity.
(b) Mask 2 is used as upper layer with 100% opac-
ity.
Dodge mode multiplies the pixel value of the lower layer by 256, then divides that by the inverse of the pixel value of the
top layer. The resulting image is usually lighter, but some colors may be inverted.
In photography, dodging is a technique used in a darkroom to increase the exposure in particular areas of the image. This
brings out details in the shadows. When used for this purpose, dodge may work best on Grayscale images and with a
painting tool, rather than as a layer mode.
The equation is:
E =
I256
(255M)+1
EQUATION 8.7: Equation for layer mode Dodge
Burn
Figure 8.15: Example for layer mode ‘Burn’
(a) Mask 1 is used as upper layer with 100% opac-
ity.
(b) Mask 2 is used as upper layer with 100% opac-
ity.
Burn mode inverts the pixel value of the lower layer, multiplies it by 256, divides that by one plus the pixel value of the
upper layer, then inverts the result. It tends to make the image darker, somewhat similar to ‘Multiply’ mode.