Image Manipulation Techniques - Blender Compositing and Post Processing - page 37

gray) is the same as multiplication by 2.0]. If the foreground is black, Blender
doesn't alter the background pixels.
• Difference : In this mode, both images are subtracted from one another and
the absolute value is displayed as the output. The output value shows the
distance between both images: black stands for equal colors and whitefor op-
posite colors. The result looks a bit strange in many cases. This mode can
be used to compare two images, and results in black if they are equal. This
mode can also be used to invert the pixels of the base image.
• Darken [Min (A, B)]: This mode results in a smaller pixel value by comparing
both image pixels. A completely white pixel does not affect the background
at all and a completely black pixel gives a black result.
• Lighten [Max (A, B)]: This mode results in a higher pixel value by comparing
both image pixels. A completely black pixel does not alter the image at all
and a completely white pixel gives a white result.
• Dodge [A/(1-B)]: This mode brightens the image by using the gradient in the
other image. It outputs lighter areas of the image where the gradient is whiter.
• Burn [1-(1-A)/B]: This mode darkens one socket image on the gradient fed
to the other image. It outputs darker images.
• Color : In this mode, each pixel is added with its color tint. This can be used
to increase the tint of the image.
• Value : In this mode, the RGB values from both images are converted to HSV
parameters. Both the pixel values are blended, and the hue and saturation of
the base image are combined with the blended value and converted to RGB.
• Saturation : In this mode, the RGB values of both images are converted to
HSV parameters. Both pixels saturations are blended, and the hue and value
of the base image are combined with the blended saturation and converted
to RGB.
• Hue : In this mode, the RGB parameters of both pixels are converted to HSV
parameters. Both pixels hues are blended, and the value and saturation of
the base image are combined with the blended hue and converted to RGB.
Use Alpha
The Use Alpha button of the Mix node instructs the Mix node to use the Alpha chan-
nel available in the foreground image. Based on the grayscale information in the al-
pha channel, the foreground pixels are made transparent to view the background
image. The effect of the selected blending mode is thus seen only in the nontrans-