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<title>6.2. Mode</title>
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<th colspan="3" align="center" id="chaptername">6.2. Mode</th>
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<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="gimp-image-mode"></a>6.2. Mode</h3>
</div>
</div>
</div>
<a id="id3351621" class="indexterm"></a>
<div class="informalfigure">
<div class="mediaobject">
<img src="../images/menus/menus-image-mode.png" />
<div class="caption">
<p>
The Mode submenu of the Image menu
</p>
</div>
</div>
</div>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id3351707"></a>Overview</h4>
</div>
</div>
</div>
<p>
This command can be accessed via the image menu:
<span class="guimenu">Image</span>/
<span class="guimenuitem"><span class="accel">M</span>ode...</span>.
</p>
<p>
It allows you to change the color
mode of your image. Three modes are available:
</p>
</div>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id3351553"></a>Mode Menuitems</h4>
</div>
</div>
</div>
<div class="variablelist">
<dl>
<dt>
<a id="gimp-image-convert-rgb"></a>
<span class="term">The RGB mode</span>
</dt>
<dd>
<p>
You are normally working in RGB mode, well adapted to
screen. See <a href="go01.html#glossary-colormodel">Glossary</a>. You can
change RGB to Grayscale or Indexed, but be careful: once the
image saved you can no longer retrieve the RGB colors. Work
on a copy.
</p>
</dd>
<dt>
<a id="gimp-image-convert-grayscale"></a>
<span class="term">The Grayscale mode</span>
</dt>
<dd>
<p>
<span class="guilabel">Grayscale</span>: Converts your image to a 256
gray level image. See the glossary for mor information about
the <a href="go01.html#glossary-colormodel">grayscale
mode</a>.
</p>
</dd>
<dt>
<a id="gimp-image-convert-indexed"></a>
<span class="term">The Indexed mode</span>
</dt>
<dd>
<p>
This option opens the <span class="guilabel">Convert Image to Indexed
Colors</span> dialog:
</p>
<div class="mediaobject">
<img src="../images/dialogs/dialogs-image-mode-indexed.png" />
</div>
</dd>
</dl>
</div>
<div class="variablelist">
<p class="title">
<b>Convert Image to Indexed Colors</b>
</p>
<p>
See <a href="go01.html#glossary-colormodel">Glossary</a> for
explanations about the Indexed Color Mode.
</p>
<dl>
<dt>
<span class="term">General Palette Options</span>
</dt>
<dd>
<div class="itemizedlist">
<ul type="opencircle">
<li style="list-style-type: circle">
<p>
<span class="guilabel">Generate Optimate Palette</span>: This
option generates the best possible palette with a
default maximum number of 256 colors (classical GIF
format). You can reduce this <span class="emphasis"><em>Maximum Number of
Colors</em></span>. This may create unwanted effects on
smooth transitions. You can reduce them by using a
dithering option.
</p>
</li>
<li style="list-style-type: circle">
<p>
<span class="guilabel">Use Black and White (1-bit)
Palette</span>: This option generates line-art
images.
</p>
</li>
<li style="list-style-type: circle">
<p>
<span class="guilabel">Use Custom Palette</span>: The button
allows you to select a custom palette in a list. The
number of colors is indicated for each palette. The Web
palette, 216 colors, is the Web-safe palette. It was
originally created by Netscape to provide colors that
would look the same on both Macs and PCs and Internet
Explorer 3 could manage it. Since version 4, MSIE
handles a 212 colors palette... This problem of color
similarity between all platforms is not solved yet and
probably will never be. You have to keep to two
principles in your Web page: light text on dark
background or dark text on light background and never
entrust an information to a color.
</p>
<p>
Some colors of the palette may not be used if your image
is poorly colored. They will be removed from the palette
if the option <span class="emphasis"><em>Remove Unused Colors from the
Final Palette</em></span> is checked.
</p>
</li>
</ul>
</div>
</dd>
<dt>
<span class="term">Dithering Options</span>
</dt>
<dd>
<p>
As an indexed image contains 256 colors or less, some colors
in the original image may be absent in the palette. This may
result in some blotchy or solid colors in subtle color
areas. These options allows you to correct these unwanted
effects induced by the Palette Options.
</p>
<p>
The filter will attempt to approximate the missing color by
spreading pixels of the nearest palette colors going
clustering. These clustered pixels seen from a distance
simulate a new color. See the glossary for more information
on <a href="go01.html#glossary-dithering">dithering</a>.
</p>
<p>
Three filters are available. It's not possible to foresee
what the result of a specific filter will be and you will
have to try all to get the best result. The
<span class="emphasis"><em>Positioned Color Dithering</em></span> is well
adapted to animations.
</p>
<div class="informalfigure">
<div class="mediaobject">
<img src="../images/dialogs/examples/dither1.png" />
<div class="caption">
<p>
Here is the image of a smooth transition as an
example.
</p>
</div>
</div>
</div>
<div class="informalfigure">
<div class="mediaobject">
<img src="../images/dialogs/examples/dither2.png" />
<div class="caption">
<p>
After transformation to GIF 4 colors without dithering.
</p>
</div>
</div>
</div>
<div class="informalfigure">
<div class="mediaobject">
<img src="../images/dialogs/examples/dither3.png" />
<div class="caption">
<p>
GIF 4 colors with Floyd-Sternberg (normal).
</p>
</div>
</div>
</div>
<div class="informalfigure">
<div class="mediaobject">
<img src="../images/dialogs/examples/dither4.png" />
<div class="caption">
<p>
GIF 4 colors with Floyd-Sternberg-2.
</p>
</div>
</div>
</div>
<p>
In a GIF image transparency is coded on 1 bit: transparent
or not transparent. To give an illusion of partial
transparency use the option <span class="guilabel">Enable Dithering of
Transparency</span>, but the semi-flatten plugin
will give you a better result.
</p>
</dd>
</dl>
</div>
</div>
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