function.imagetruecolortopalette.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Convert a true color image to a palette image</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.imagesy.html">imagesy</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.imagettfbbox.html">imagettfbbox</a></div> <div class="up"><a href="ref.image.html">GD Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="function.imagetruecolortopalette" class="refentry"> <div class="refnamediv"> <h1 class="refname">imagetruecolortopalette</h1> <p class="verinfo">(PHP 4 >= 4.0.6, PHP 5)</p><p class="refpurpose"><span class="refname">imagetruecolortopalette</span> — <span class="dc-title">Convert a true color image to a palette image</span></p> </div> <div class="refsect1 description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">bool</span> <span class="methodname"><b><b>imagetruecolortopalette</b></b></span> ( <span class="methodparam"><span class="type">resource</span> <tt class="parameter">$image</tt></span> , <span class="methodparam"><span class="type">bool</span> <tt class="parameter">$dither</tt></span> , <span class="methodparam"><span class="type">int</span> <tt class="parameter">$ncolors</tt></span> )</div> <p class="para rdfs-comment"> <b>imagetruecolortopalette()</b> converts a truecolor image to a palette image. The code for this function was originally drawn from the Independent JPEG Group library code, which is excellent. The code has been modified to preserve as much alpha channel information as possible in the resulting palette, in addition to preserving colors as well as possible. This does not work as well as might be hoped. It is usually best to simply produce a truecolor output image instead, which guarantees the highest output quality. </p> </div> <div class="refsect1 parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt><span class="term"><i><tt class="parameter">image</tt></i></span><dd><p class="para">An image resource, returned by one of the image creation functions, such as <a href="function.imagecreatetruecolor.html" class="function">imagecreatetruecolor()</a>.</p></dd></dt> <dt> <span class="term"><i><tt class="parameter">dither</tt></i></span> <dd> <p class="para"> Indicates if the image should be dithered - if it is <b><tt>TRUE</tt></b> then dithering will be used which will result in a more speckled image but with better color approximation. </p> </dd> </dt> <dt> <span class="term"><i><tt class="parameter">ncolors</tt></i></span> <dd> <p class="para"> Sets the maximum number of colors that should be retained in the palette. </p> </dd> </dt> </dl> </p> </div> <div class="refsect1 returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> Returns <b><tt>TRUE</tt></b> on success or <b><tt>FALSE</tt></b> on failure. </p> </div> <div class="refsect1 examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example"> <p><b>Example #1 Converting a true color image to a palette-based image</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// Create a new true color image<br /></span><span style="color: #0000BB">$im </span><span style="color: #007700">= new </span><span style="color: #0000BB">imagecreatetruecolor</span><span style="color: #007700">(</span><span style="color: #0000BB">100</span><span style="color: #007700">, </span><span style="color: #0000BB">100</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Convert to palette-based with no dithering and 255 colors<br /></span><span style="color: #0000BB">imagetruecolortopalette</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">, </span><span style="color: #0000BB">false</span><span style="color: #007700">, </span><span style="color: #0000BB">255</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Save the image<br /></span><span style="color: #0000BB">imagepng</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">, </span><span style="color: #DD0000">'./paletteimage.png'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">imagedestroy</span><span style="color: #007700">(</span><span style="color: #0000BB">$im</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> </p> </div> <div class="refsect1 notes"> <h3 class="title">Notes</h3> <blockquote><p><b class="note">Note</b>: <span class="simpara">This function requires GD 2.0.1 or later (2.0.28 or later is recommended).</span></p></blockquote> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.imagesy.html">imagesy</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.imagettfbbox.html">imagettfbbox</a></div> <div class="up"><a href="ref.image.html">GD Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>⌨️ 快捷键说明
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