User Guide

GNU Image Manipulation Program
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E = 1 −
(255−M)∗(255−I)
255
EQUATION 8.5: Equation for layer mode Screen
The mode is commutative; the order of the two layers doesn’t matter.
Overlay
Figure 8.13: Example for layer mode ‘Overlay’
(a) Mask 1 is used as upper layer with 100% opac-
ity.
(b) Mask 2 is used as upper layer with 100% opac-
ity.
Overlay mode inverts the pixel value of the lower layer, multiplies it by two times the pixel value of the upper layer, adds
that to the original pixel value of the lower layer, divides by 255, and then multiplies by the pixel value of the original
lower layer and divides by 255 again. It darkens the image, but not as much as with ‘Multiply’ mode.
The equation is:
1
E =
1I
255
∗ (I +
2M
255
∗ (255 −I))
EQUATION 8.6: Equation for layer mode Overlay
Dodge
1
The equation is the *theoretical* equation. Due to Bug #162395 , the actual equation is equivalent to Soft light. It is difficult to fix this bug without changing
the appearance of existing images.