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<h1>RGB &amp; HSV Colorspaces</h1>

<p>Both the RGB and HSV Colorspaces define a method of uniquely
specifying colors via three numbers.</p>

<p>The RGB colorspace is the more commonly used of the two. For
example, most color monitors operate on RGB inputs. In RGB
colorspace, each color is represented by a three number 'triple'.
The components of this triple specify, respectively, the amount
of red, the amount of green, and the amount of blue in the color.
In most computer graphics systems (and in <i>xv</i>), these
values are represented as 8-bit unsigned numbers. Thus, each
component has a range of 0-255, inclusive, with 0 meaning 'no
output', and 255 meaning 'full output'.</p>

<p>The eight 'primary' colors in the RGB colorspace, and their
values in the standard 8-bit unsigned range are:</p>

<blockquote>
    <pre><font size="2">Black    (  0,  0,  0)
Red      (255,  0,  0)
Green    (  0,255,  0)
Yellow   (255,255,  0)
Blue     (  0,  0,255)
Magenta  (255,  0,255)
Cyan     (  0,255,255)
White    (255,255,255)</font></pre>
</blockquote>

<p>Other colors are specified by intermediate values. For
example, <i>orange</i> is chromatically between red and yellow on
the color spectrum. To get an <i>orange</i>, you can simply
average <i>red</i> (255,0,0) and <i>yellow</i> (255,255,0) on a
component-by-component basis resulting in (255,127,0), which will
be some <i>orange</i>-ish color.</p>

<p>You can change the brightness of the colors by raising or
lowering all of their components by some factor. For example, if
(0,255,255) is <i>cyan</i> (it is), then (0,128,128) would be a <i>dark
cyan</i>.</p>

<p>Saturation of a color is a measure of how 'pure' the color is.
Desaturated colors will appear washed-out, or pastel, whereas
saturated colors will be bold and vibrant, the sort of colors
you'd paint a sports car. In the RGB colorspace, you can
desaturate colors by adding <i>white</i> to them. For example, if
you take <i>red</i> (255,0,0), and add a <i>medium grey</i> to it
(128,128,128), you'll get a shade of <i>pink</i> (255,128,128).
Note that the component values are 'clipped' to remain in the
range 0-255.</p>

<p>The HSV colorspace works somewhat differently. It is
considered by many to be more intuitive to use, closer to how an
artist actually mixes colors.</p>

<p>In the HSV colorspace, each color is again determined by a
three-component 'triple'. The first component, <i>Hue</i>,
describes the basic color in terms of its angular position on a
'color wheel'. In this particular implementation, Hue is
described in terms of degrees.</p>

<p>Unfortunately, since this document isn't printed in color, it
is not possible to show this 'color wheel' in any meaningful way.
Here is where the 'primary' colors live:</p>

<blockquote>
    <pre>Red       0
Yellow   60
Green   120
Cyan    180
Blue    240
Magenta 300
</pre>
</blockquote>

<p>The colors appear in the same order that they do on a standard
color spectrum, except that they form a circle, with magenta
looping back to red.</p>

<p>As with the RGB space, in-between colors are represented by
in-between values. For example, <i>orange</i> would have a Hue
value of 30, being situated roughly halfway between <i>red</i>
and <i>yellow</i>. </p>

<p>The second component of the HSV triple is <i>Saturation</i>,
which, as described above, can be thought of as &quot;how pure
the color is&quot;. In this implementation, saturation can range
between 0 and 100, inclusive. Colors with a saturation of 100 are
fully-saturated, whereas colors with a saturation of 0 are
completely desaturated (in other words, <i>grey</i>).</p>

<p>The third component of the HSV triple is <i>Value</i> , which
really should be called <i>Intensity</i>. It is a measure of how
'bright' the color is. In this implementation, Value can range
between 0 and 100, inclusive. A color with a Value component of
100 will be as bright as possible, and a color with a Value
component of 0 will be as dark as possible (i.e., <i>black</i>). </p>

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