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<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="gimp-layer-colors-menu"></a>7.3. Colors</h3>
</div>
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</div>
<div class="informalfigure">
<div class="mediaobject">
<img src="../images/menus/menus-layer-colors.png" />
<div class="caption">
<p>
The Color submenu
</p>
</div>
</div>
</div>
<p>
The Color submenu of the Layers menu contains operations that
alter colors within the image. The top entries give access to
the <a href="ch03s05.html" title="5. Color Tools">Color tools</a>, which
are described in the Toolbox chapter.
</p>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="gimp-layer-desaturate"></a>Desaturate</h4>
</div>
</div>
</div>
<p>
This command can be accessed from an image menubar as
<span class="guimenu">Layers</span>-><span class="guisubmenu">Color</span>-><span class="guimenuitem">Desaturate</span>.
</p>
<p>
"Desaturate" causes all colors in the active layer to be
converted to correspondingly bright shades of gray. It differs
from converting the image to grayscale in two respects: first,
it only operates on the active layer; second, the colors in the
layer continue to be three-component RGB colors, and nothing
prevents you from painting the desaturated layer with any colors
you please. Desaturate works only on layers from RGB images; if
the image is Grayscale or Indexed, the menu entry will be
insensitive.
</p>
</div>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="gimp-layer-invert"></a>Invert</h4>
</div>
</div>
</div>
<p>
This command can be accessed from an image menubar as
<span class="guimenu">Layers</span>-><span class="guisubmenu">Color</span>-><span class="guimenuitem">Invert</span>.
</p>
<p>
"Invert" causes all colors in the active layer to be
inverted in brightness, as though the image were converted into
a negative. Dark areas turn to bright and conversely; hues are
replaced by their complement (for more informations about colors see
glossary at <a href="go01.html#glossary-colormodel">Color Model</a>).
Invert works on layers from RGB and Grayscale images, but if the
image is Indexed, the menu entry will be insensitive.
</p>
</div>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id3354176"></a>Submenu: Auto</h4>
</div>
</div>
</div>
<div class="informalfigure">
<div class="mediaobject">
<img src="../images/menus/menus-layer-colors-auto.png" />
<div class="caption">
<p>
The Colors/Auto submenu
</p>
</div>
</div>
</div>
<p>
The Layers/Colors/Auto submenu contains operations that
automatically adjust the distribution of colors in the active
layer, without requiring input from the user. Several of them
are actually implemented as plugins.
</p>
</div>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="gimp-layer-equalize"></a>Equalize</h4>
</div>
</div>
</div>
<p>
This command can be accessed from an image menubar as
<span class="guimenu">Layers</span>-><span class="guisubmenu">Color</span>-><span class="guisubmenu">Auto</span>-><span class="guimenuitem">Equalize</span>.
</p>
<p>
"Equalize" adjusts the brightness of colors across the active
layer so that the histogram for the Value channel is as nearly
as possible flat, that is, so that each possible brightness
value appears at about the same number of pixels as each other
value. Sometimes Equalize works wonderfully at enhancing the
contrasts in an image. Other times it gives garbage. It is a
very powerful operation, which can either work miracles on an
image or destroy it.
</p>
</div>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="plug-in-color-enhance"></a>Color Enhance</h4>
</div>
</div>
</div>
<p>
This command can be accessed from an image menubar as
<span class="guimenu">Layers</span>-><span class="guisubmenu">Color</span>-><span class="guisubmenu">Auto</span>-><span class="guimenuitem">Color Enhance</span>.
</p>
<p>
"Color Enhance" increases the saturation range of colors in the
layer without altering brightness or hue. It does this by
converting the colors in HSV space, measuring the range of
saturation values across the image, then stretching this range
to be as large as possible, and finally converting the colors
back to RGB. It works on layers from RGB and Indexed images. If the
image is Grayscale, the menu entry will be
insensitive.
</p>
</div>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="plug-in-normalize"></a>Normalize</h4>
</div>
</div>
</div>
<p>
This command can be accessed from an image menubar as
<span class="guimenu">Layers</span>-><span class="guisubmenu">Color</span>-><span class="guisubmenu">Auto</span>-><span class="guimenuitem">Normalize</span>.
</p>
<p>
"Normalize" scales brightness values across the active layer so that
the darkest point becomes black, and the brightest point becomes
as bright as possible without altering its hue. This is often a
"magic fix" for images that are dim or washed out. Normalize
works on layers from RGB, Grayscale, and Indexed images.
</p>
</div>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="plug-in-c-astretch"></a>Stretch Contrast</h4>
</div>
</div>
</div>
<p>
This command can be accessed from an image menubar as
<span class="guimenu">Layers</span>-><span class="guisubmenu">Color</span>-><span class="guisubmenu">Auto</span>-><span class="guimenuitem">Stretch Contrast</span>.
</p>
<p>
"Stretch Contrast" is somewhat similar to Normalize in its
effects, except that it works on each color channel of the layer
individually, rather than just the brightness values. This
usually leads to color shifts within the image, so it may not
produce the result you are looking for. Stretch Contrast
operates on layers from RGB, Grayscale, and Indexed images.
</p>
</div>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="plug-in-autostretch-hsv"></a>Stretch HSV</h4>
</div>
</div>
</div>
<p>
This command can be accessed from an image menubar as
<span class="guimenu">Layers</span>-><span class="guisubmenu">Color</span>-><span class="guisubmenu">Auto</span>-><span class="guimenuitem">Stretch HSV</span>.
</p>
<p>
"Stretch HSV" does the same thing as "Stretch Contrast", except
that it works in HSV color space rather than RGB color space.
Thus, it independently stretches the hue channel, the saturation
channel, and the value channel. Occasionally the results are
good, often they are a bit odd. Stretch HSV operates on layers
from RGB and Indexed images. If the image is Grayscale, the
menu entry will be insensitive.
</p>
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