Two options and differences in using GD to generate thumbnails under PHP

PHP的GD扩展提供了两个函数来缩放图像：

<span lang="EN-US">ImageCopyResized(<tt><em>dest</em></tt>, <tt><em>src</em></tt>, <tt><em>dx</em></tt>, <tt><em>dy</em></tt>, <tt><em>sx</em></tt>, <tt><em>sy</em></tt>, <tt><em>dw</em></tt>, <tt><em>dh</em></tt>, <tt><em>sw</em></tt>, <tt><em>sh</em></tt>);<br>ImageCopyResampled(<tt><em>dest</em></tt>, <tt><em>src</em></tt>, <tt><em>dx</em></tt>, <tt><em>dy</em></tt>, <tt><em>sx</em></tt>, <tt><em>sy</em></tt>, <tt><em>dw</em></tt>, <tt><em>dh</em></tt>, <tt><em>sw</em></tt>, <tt><em>sh</em></tt>);</span> <br>

Copy after login

<span style="COLOR: rgb(0,0,0)"><span style="COLOR: rgb(0,119,0)"><span style="COLOR: rgb(0,0,0)">
<p><code><span style="COLOR: rgb(0,0,0)"><span style="COLOR: rgb(0,119,0)"><span style="COLOR: rgb(0,0,0)"></span></span></span>

ImageCopyResized( ) function works in all GD versions, but its scaling The algorithm of the image is relatively rough and may cause jagged edges of the image. GD 2.x has a new ImageCopyResampled( ) function. The image edges obtained by its pixel interpolation algorithm are relatively smooth (but this function is slower than ImageCopyResized()Slow).

来看一个例子，我们将这个图缩小四倍：

<span style="COLOR: rgb(0,0,0)"><span style="COLOR: rgb(0,0,187)"><?php <br><br> $src </SPAN><SPAN style="COLOR: rgb(0,119,0)">= </SPAN><SPAN style="COLOR: rgb(0,0,187)">ImageCreateFromJPEG</SPAN><SPAN style="COLOR: rgb(0,119,0)">(</SPAN><SPAN style="COLOR: rgb(221,0,0)">'php.jpg'</SPAN><SPAN style="COLOR: rgb(0,119,0)">); <br><br> </SPAN><SPAN style="COLOR: rgb(0,0,187)">$width </SPAN><SPAN style="COLOR: rgb(0,119,0)">= </SPAN><SPAN style="COLOR: rgb(0,0,187)">ImageSx</SPAN><SPAN style="COLOR: rgb(0,119,0)">(</SPAN><SPAN style="COLOR: rgb(0,0,187)">$src</SPAN><SPAN style="COLOR: rgb(0,119,0)">); <BR> </SPAN><SPAN style="COLOR: rgb(0,0,187)">$height </SPAN><SPAN style="COLOR: rgb(0,119,0)">= </SPAN><SPAN style="COLOR: rgb(0,0,187)">ImageSy</SPAN><SPAN style="COLOR: rgb(0,119,0)">(</SPAN><SPAN style="COLOR: rgb(0,0,187)">$src</SPAN><SPAN style="COLOR: rgb(0,119,0)">); <BR> </SPAN><SPAN style="COLOR: rgb(0,0,187)">$x </SPAN><SPAN style="COLOR: rgb(0,119,0)">= </SPAN><SPAN style="COLOR: rgb(0,0,187)">$width</SPAN><SPAN style="COLOR: rgb(0,119,0)">/</SPAN><SPAN style="COLOR: rgb(0,0,187)">2</SPAN><SPAN style="COLOR: rgb(0,119,0)">; </SPAN><SPAN style="COLOR: rgb(0,0,187)">$y </SPAN><SPAN style="COLOR: rgb(0,119,0)">= </SPAN><SPAN style="COLOR: rgb(0,0,187)">$height</SPAN><SPAN style="COLOR: rgb(0,119,0)">/</SPAN><SPAN style="COLOR: rgb(0,0,187)">2</SPAN><SPAN style="COLOR: rgb(0,119,0)">; <BR> </SPAN><SPAN style="COLOR: rgb(0,0,187)">$dst </SPAN><SPAN style="COLOR: rgb(0,119,0)">= </SPAN><SPAN style="COLOR: rgb(0,0,187)">ImageCreateTrueColor</SPAN><SPAN style="COLOR: rgb(0,119,0)">(</SPAN><SPAN style="COLOR: rgb(0,0,187)">$x</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">$y</SPAN><SPAN style="COLOR: rgb(0,119,0)">); <BR> </SPAN><SPAN style="COLOR: rgb(0,0,187)">ImageCopyResized</SPAN><SPAN style="COLOR: rgb(0,119,0)">(</SPAN><SPAN style="COLOR: rgb(0,0,187)">$dst</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">$src</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">0</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">0</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">0</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">0</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">$x</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">$y</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">$width</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">$height</SPAN><SPAN style="COLOR: rgb(0,119,0)">); <BR> </SPAN><SPAN style="COLOR: rgb(255,128,0)">//ImageCopyResampled($dst,$src,0,0,0,0,$x,$y,$width,$height); <br><br> </SPAN><SPAN style="COLOR: rgb(0,0,187)">header</SPAN><SPAN style="COLOR: rgb(0,119,0)">(</SPAN><SPAN style="COLOR: rgb(221,0,0)">'Content-Type: image/jpeg'</SPAN><SPAN style="COLOR: rgb(0,119,0)">); <BR> </SPAN><SPAN style="COLOR: rgb(0,0,187)">ImageJPEG</SPAN><SPAN style="COLOR: rgb(0,119,0)">(</SPAN><SPAN style="COLOR: rgb(0,0,187)">$dst</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(221,0,0)">''</SPAN><SPAN style="COLOR: rgb(0,119,0)">,</SPAN><SPAN style="COLOR: rgb(0,0,187)">100</SPAN><SPAN style="COLOR: rgb(0,119,0)">); <BR></SPAN><SPAN style="COLOR: rgb(0,0,187)">?></span> <br><br>原图：<br><img alt="" src="http://www.bkjia.com/uploads/allimg/131016/061UI255-0.jpg"><br><br>使用</span>

<span   style="max-width:90%"><span style="COLOR: rgb(0,119,0)"></span><span style="COLOR: rgb(0,0,187)">ImageCopyResized</span><span style="COLOR: rgb(0,119,0)">()<span style="COLOR: rgb(0,0,0)">函数生成的结果：<br><img alt="" src="http://www.bkjia.com/uploads/allimg/131016/061UIT1-1.jpg"><br><br><br></span></span></span>

使用

<span style="COLOR: rgb(0,0,0)"><span style="COLOR: rgb(0,119,0)"></span><span style="COLOR: rgb(0,0,187)">ImageCopyResampled</span><span style="COLOR: rgb(0,119,0)">()<span style="COLOR: rgb(0,0,0)">函数生成的结果：</span></span></span>

<span style="COLOR: rgb(0,0,0)"><span style="COLOR: rgb(0,119,0)"><span style="COLOR: rgb(0,0,0)"><br></span><br></span><span style="COLOR: rgb(0,0,187)"></span></span>

很明显可以看到两个函数生成的图像效果是不一样的，

<span   style="max-width:90%"><span style="COLOR: rgb(0,0,187)">ImageCopyResampled</span><span style="COLOR: rgb(0,119,0)">()<span style="COLOR: rgb(0,0,0)">函数生成的结果比较平滑，效果较好。<br><br></span></span></span>

<span style="COLOR: rgb(0,0,0)"><span style="COLOR: rgb(0,119,0)"><span style="COLOR: rgb(0,0,0)"><code><span style="COLOR: rgb(0,0,0)"><span style="COLOR: rgb(0,119,0)"><span style="COLOR: rgb(0,0,0)"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&lt;font size=&quot;2&quot;&gt;顺便贴一个效果，用ASCII表示图像。ImageColorAt()有一个很有趣的用处，它可以循环检查&lt;br&gt;&lt;/font&gt;&lt;font size=&quot;2&quot;&gt;图像中的每一个像素的颜色，然后对该颜色数据进行操作。&lt;/font&gt;</pre><div class="contentsignin">Copy after login</div></div>
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&lt;font face=&quot;宋体&quot; size=&quot;2&quot;&gt;&lt;span style=&quot;FONT-SIZE: 12pt&quot;&gt;源代码：&lt;br&gt;&lt;/span&gt;&lt;/font&gt;&lt;font face=&quot;Courier New&quot;&gt;&lt;html&gt;&lt;/font&gt;</pre><div class="contentsignin">Copy after login</div></div>
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">&lt;font face=&quot;Courier New&quot;&gt;&lt;body bgcolor=&quot;#000000&quot; style=&quot;line-height:6pt&quot;&gt; &lt;/font&gt;&lt;font face=&quot;Courier New&quot;&gt;&lt;span style=&quot;COLOR: rgb(0,0,187)&quot;&gt;&lt;?php &lt;BR&gt; $im &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;= &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;imagecreatefromjpeg&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;(&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(221,0,0)&quot;&gt;'test1.jpg'&lt;/SPAN&gt;&lt;/FONT&gt;&lt;FONT face=&quot;Courier New&quot;&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;); &lt;BR&gt; &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$dx &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;= &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;imagesx&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;(&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$im&lt;/SPAN&gt;&lt;/FONT&gt;&lt;FONT face=&quot;Courier New&quot;&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;); &lt;BR&gt; &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$dy &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;= &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;imagesy&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;(&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$im&lt;/SPAN&gt;&lt;/FONT&gt;&lt;FONT face=&quot;Courier New&quot;&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;); &lt;BR&gt; for(&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$y &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;= &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;0&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;; &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$y &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;&lt; &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$dy&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;; &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$y&lt;/SPAN&gt;&lt;/FONT&gt;&lt;FONT face=&quot;Courier New&quot;&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;++) { &lt;BR&gt;     for(&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$x&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;=&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;0&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;; &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$x &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;&lt; &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$dx&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;; &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$x&lt;/SPAN&gt;&lt;/FONT&gt;&lt;FONT face=&quot;Courier New&quot;&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;++) { &lt;BR&gt;         &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$col &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;= &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;imagecolorat&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;(&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$im&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;, &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$x&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;, &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$y&lt;/SPAN&gt;&lt;/FONT&gt;&lt;FONT face=&quot;Courier New&quot;&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;); &lt;BR&gt;         &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$rgb &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;= &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;imagecolorsforindex&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;(&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$im&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;,&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$col&lt;/SPAN&gt;&lt;/FONT&gt;&lt;FONT face=&quot;Courier New&quot;&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;); &lt;BR&gt;         &lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,0,187)&quot;&gt;printf&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(0,119,0)&quot;&gt;(&lt;/SPAN&gt;&lt;SPAN style=&quot;COLOR: rgb(221,0,0)&quot;&gt;'&lt;font color=#%02x%02x%02x&gt;*&lt;/font&gt;'&lt;/span&gt;&lt;/font&gt;&lt;font face=&quot;Courier New&quot;&gt;&lt;span style=&quot;COLOR: rgb(0,119,0)&quot;&gt;, &lt;br&gt;                 &lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$rgb&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,119,0)&quot;&gt;[&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(221,0,0)&quot;&gt;'red'&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,119,0)&quot;&gt;],&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$rgb&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,119,0)&quot;&gt;[&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(221,0,0)&quot;&gt;'green'&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,119,0)&quot;&gt;],&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$rgb&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,119,0)&quot;&gt;[&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(221,0,0)&quot;&gt;'blue'&lt;/span&gt;&lt;/font&gt;&lt;font face=&quot;Courier New&quot;&gt;&lt;span style=&quot;COLOR: rgb(0,119,0)&quot;&gt;]); &lt;br&gt;     } &lt;br&gt;     echo &lt;/span&gt;&lt;span style=&quot;COLOR: rgb(221,0,0)&quot;&gt;&quot;&lt;br&gt;\n&quot;&lt;/span&gt;&lt;/font&gt;&lt;font face=&quot;Courier New&quot;&gt;&lt;span style=&quot;COLOR: rgb(0,119,0)&quot;&gt;; &lt;br&gt; } &lt;br&gt; &lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,0,187)&quot;&gt;imagedestroy&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,119,0)&quot;&gt;(&lt;/span&gt;&lt;span style=&quot;COLOR: rgb(0,0,187)&quot;&gt;$im&lt;/span&gt;&lt;/font&gt;&lt;span style=&quot;COLOR: rgb(0,119,0)&quot;&gt;&lt;font face=&quot;Courier New&quot;&gt;); &lt;br&gt;&lt;/font&gt;&lt;/span&gt;&lt;font face=&quot;Courier New&quot;&gt;&lt;span style=&quot;COLOR: rgb(0,0,187)&quot;&gt;?&gt; &lt;br&gt;&lt;/span&gt;&lt;/body&gt;&lt;/html&gt; &lt;/font&gt;</pre><div class="contentsignin">Copy after login</div></div>
<p><br></p>
<p><img alt="" src="http://www.bkjia.com/uploads/allimg/131016/061UH1N-3.gif"></p></span></span></span>

很有趣吧，呵呵..

Two options and differences in using GD to generate thumbnails under PHP_PHP Tutorial