User Manual - twentynine
8.2.8
GIMP HSL
The
GIMP HSL
algorithm allows the color manipulation of images based on the HSL color space. The used
algorithm is provided by the open source project GIMP and allows the manipulation by the attributes
Hue,
Saturation and Lightness
.
When it comes to manipulating color in images it is often referred to color models or color spaces. Basically
a color model describes the way colors can be represented. With understanding of how different color
models work, the appropriate color model for specific image processing algorithms can be chosen. The
most widely used and best known one is the RGB color model. However, RGB is not always efficient and
intuitive in manipulating color.
A more suited color space for manipulating colors is the HSL color space. It was developed to interpret colors
in a very similar way as humans do, wherefore color and brightness information are handled separately. The
color information is defined by
Hue
and
Saturation
, the brightness information is defined by a
Lightness
value. The HSL color model can be represented by a circle called a color wheel like shown in Figure 113.
300°
Red
0°
Green
Cyan
Blue
60°
120°
180°
240°
Yellow
Magenta
Hue
Figure 113: HSL color wheel
Hue
refers to a specific tone of color: Red, Yellow, Green, Cyan, Blue, Magenta and their blends, the
individual colors are arranged in a circle. Their individual position is determined by an angle, ranging from
0
◦
to 360
◦
. Pure red is usually placed at 0
◦
, pure green and pure blue at 120
◦
respectively 240
◦
. Table 60
shows the six base colors.
136
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