如何利用imagegif() 配合imagecreate() 創建並輸出GIF 圖片？

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<h1>如何利用 </span><span><span class="hljs-title function_ invoke__">imagegif</span></span><span>() 配合 </span><span><span class="hljs-title function_ invoke__">imagecreate</span></span><span>() 創建並輸出 GIF 圖片？</h1>

<p>在 PHP 的圖像處理擴展 GD 庫中，<code></span><span><span class="hljs-title function_ invoke__">imagecreate</span></span><span>()

其中， $width和$height分別表示圖像的寬度和高度。創建成功後，就可以在這個畫布上進行繪製操作。

2 . imagecolorallocate () 分配顏色

在生成畫布後，我們需要為圖像分配顏色。 imagecolorallocate()函數用於在圖像中創建一種顏色，其語法為：

 </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-title function_ invoke__">imagecolorallocate</span></span><span> ( resource </span><span><span class="hljs-variable">$image</span></span><span> , </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$red</span></span><span> , </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$green</span></span><span> , </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$blue</span></span><span> )

例如， imagecolorallocate($img, 255, 0, 0)表示在圖像中創建紅色。

3 . imagegif () 輸出圖像

imagegif()函數負責將圖像輸出為GIF 格式，可以直接輸出到瀏覽器，也可以保存為文件。語法為：

 </span><span><span class="hljs-keyword">bool</span></span><span> </span><span><span class="hljs-title function_ invoke__">imagegif</span></span><span> ( resource </span><span><span class="hljs-variable">$image</span></span><span> [, </span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$filename</span></span><span> ] )

如果省略$filename ，則圖像會直接輸出到瀏覽器。

4 . 示例代碼

下面我們通過示例演示如何利用imagecreate()和imagegif()來創建一張簡單的GIF 圖片：

 <?php
</span><span><span class="hljs-comment">// 告訴瀏覽器輸出的是 GIF 圖片</span></span><span>
</span><span><span class="hljs-title function_ invoke__">header</span></span><span>(</span><span><span class="hljs-string">"Content-Type: image/gif"</span></span><span>);

</span><span><span class="hljs-comment">// 創建一個 200x100 的畫布</span></span><span>
</span><span><span class="hljs-variable">$img</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreate</span></span><span>(</span><span><span class="hljs-number">200</span></span><span>, </span><span><span class="hljs-number">100</span></span><span>);

</span><span><span class="hljs-comment">// 分配背景顏色（白色）</span></span><span>
</span><span><span class="hljs-variable">$white</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecolorallocate</span></span><span>(</span><span><span class="hljs-variable">$img</span></span><span>, </span><span><span class="hljs-number">255</span></span><span>, </span><span><span class="hljs-number">255</span></span><span>, </span><span><span class="hljs-number">255</span></span><span>);

</span><span><span class="hljs-comment">// 分配繪製顏色（藍色）</span></span><span>
</span><span><span class="hljs-variable">$blue</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecolorallocate</span></span><span>(</span><span><span class="hljs-variable">$img</span></span><span>, </span><span><span class="hljs-number">0</span></span><span>, </span><span><span class="hljs-number">0</span></span><span>, </span><span><span class="hljs-number">255</span></span><span>);

</span><span><span class="hljs-comment">// 在畫布上寫文字</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagestring</span></span><span>(</span><span><span class="hljs-variable">$img</span></span><span>, </span><span><span class="hljs-number">5</span></span><span>, </span><span><span class="hljs-number">50</span></span><span>, </span><span><span class="hljs-number">40</span></span><span>, </span><span><span class="hljs-string">"Hello GIF"</span></span><span>, </span><span><span class="hljs-variable">$blue</span></span><span>);

</span><span><span class="hljs-comment">// 輸出為 GIF 格式</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagegif</span></span><span>(</span><span><span class="hljs-variable">$img</span></span><span>);

</span><span><span class="hljs-comment">// 釋放資源</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$img</span></span><span>);
?&gt;

5 . 總結

通過imagecreate()創建畫布，使用imagecolorallocate()分配顏色，再配合imagegif()輸出圖像，就能輕鬆生成GIF 圖片。這個方法常用於驗證碼、動態圖表或其他需要動態生成圖片的場景。