User Guide

GNU Image Manipulation Program
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In photography, burning is a technique used in a darkroom to decrease the exposure in particular areas of the image. This
brings out details in the highlights. When used for this purpose, burn may work best on Grayscale images and with a
painting tool, rather than as a layer mode.
The equation is:
E = 255 −
(255−I)∗256
M+1
EQUATION 8.8: Equation for layer mode Burn
Hard light
Figure 8.16: Example for layer mode ‘Hard light’
(a) Mask 1 is used as upper layer with 100% opac-
ity.
(b) Mask 2 is used as upper layer with 100% opac-
ity.
Hard light mode is rather complicated because the equation consists of two parts, one for darker colors and one for brighter
colors. If the pixel color of the upper layer is greater than 128, the layers are combined according to the first formula
shown below. Otherwise, the pixel values of the upper and lower layers are multiplied together and multiplied by two, then
divided by 256. You might use this mode to combine two photographs and obtain bright colors and sharp edges.
The equation is complex and different according to the value >128 or ≤128 :
M > 128 : E = 255 −
(255−I)∗(255−(2∗(M−128)))
256
EQUATION 8.9: Equation for layer mode Hard light, M > 128
M ≤ 128 : E =
I∗M∗2
256
EQUATION 8.10: Equation for layer mode Hard light, M ≤ 128
Soft light