User Guide

GNU Image Manipulation Program
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The equation is:
E = min((M + I), 255)
EQUATION 8.16: Equation for layer mode Addition
The mode is commutative; the order of the two layers doesn’t matter.
Subtract
Figure 8.22: Example for layer mode ‘Subtract’
(a) Mask 1 is used as upper layer with 100% opac-
ity.
(b) Mask 2 is used as upper layer with 100% opac-
ity.
Subtract mode subtracts the pixel values of the upper layer from the pixel values of the lower layer. The resulting image
is normally darker. You might get a lot of black or near-black in the resulting image. The equation can result in negative
color values, so some of the dark colors may be set to the minimum value of 0.
The equation is:
E = max((I M), 0)
EQUATION 8.17: Equation for layer mode Subtraction
Darken only