User Guide

GNU Image Manipulation Program
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15.3.14.2 Options
Figure 15.50: ‘Decompose’ filter options
Decompose to Layers If this option is checked, a new grey-scaled image is created, with each layer representing one of the
channels of the selected mode. If this option is not checked, every channel is represented with a specific image automati-
cally and clearly named in the name bar.
Following options are described with ‘Decompose to layers ’checked.
RGB Decomposing If the RGB radio button is clicked, a grey level image is created with three layers (Red, Green and Blue),
and two channels (Grey and Alpha).
This function is interesting when using Threshold tool. You can also perform operations like cutting, pasting or moving
selections in a single RBG channel. You can use an extracted grayscale as a selection or mask by saving it in a channel
(right-click>Select>Save to a channel).
RGBA Decomposing If the RGBA radio button is clicked, a image is created similar at the RGB Decomposing with a additional
Alpha layer filled with the transparencies values of the source image. Full transparent pixels are black and the full opaque
pixels are white.
HSV Decomposing This option decomposes image into three greyscaled layers, one for Hue, one for Saturation and another for
Value.
Although Hue is greyscaled, it does represent hues. In color circle, white and black are starting and arrival points and are
superimposed. They represent Red color at top of circle. Grey intermediate levels are corresponding to intermediate hues
on circle: dark grey to orange, mid grey to green and light grey to magenta.
Saturation and Value: White is maximum Saturation (pure color) and maximum Value (very bright). Black is minimum
Saturation (white) and minimum Value (black).
CMY Decomposing This option decomposes image into three greyscaled layers, one for Yellow, one for Magenta and another
for Cyan.
This option might be useful to transfer image into printing softwares with CMY capabilities.
CMYK Decomposing This option is similar at the CMY Decomposing with an additional layer for Black.
This option might be useful to transfer image into printing softwares with CMYK capabilities.
Alpha Decomposing This option extracts the image transparency stored in the Alpha channel in Channel dialog in a separate
image. The full transparent pixels are Black the full opaque pixels are white. The graytones are smooth transitions of the
transparency in the source image.