imagewbmp函数结合imagecopy函数怎样制作复杂的图像效果？实用案例分享

在PHP中，图像处理一直是非常重要的功能之一，尤其在网站开发、动态生成图像、或者图像编辑方面。PHP 提供了多种图像处理函数，而 imagewbmp 和 imagecopy 是其中两个非常实用的函数，它们常常被用来创建或编辑图像。

一、imagewbmp函数简介

imagewbmp 是 PHP GD 库中用于将图像输出为 WBMP 格式的函数。WBMP（Wireless Bitmap）是一种低质量、低色深的图像格式，通常用于移动设备或老式浏览器。imagewbmp 函数的作用是将 GD 图像资源转换成 WBMP 格式并输出。

语法：

<span><span><span class="hljs-keyword">bool</span></span><span> </span><span><span class="hljs-title function_ invoke__">imagewbmp</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> = </span><span><span class="hljs-literal">NULL</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$threshold</span></span><span> = </span><span><span class="hljs-number">128</span></span><span>);
</span></span>

• $image：要输出的图像资源。

• $filename：保存图像的路径。如果不提供，图像将直接输出到浏览器。

• $threshold：可选参数，设置阈值来确定像素是否为黑色。默认值是 128，值越小图像越黑。

使用示例：

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 创建一个空白图像</span></span><span>
</span><span><span class="hljs-variable">$image</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreatetruecolor</span></span><span>(</span><span><span class="hljs-number">100</span></span><span>, </span><span><span class="hljs-number">100</span></span><span>);

</span><span><span class="hljs-comment">// 设置背景颜色</span></span><span>
</span><span><span class="hljs-variable">$bgColor</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecolorallocate</span></span><span>(</span><span><span class="hljs-variable">$image</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-title function_ invoke__">imagefill</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>, </span><span><span class="hljs-number">0</span></span><span>, </span><span><span class="hljs-number">0</span></span><span>, </span><span><span class="hljs-variable">$bgColor</span></span><span>);

</span><span><span class="hljs-comment">// 设置前景色</span></span><span>
</span><span><span class="hljs-variable">$black</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecolorallocate</span></span><span>(</span><span><span class="hljs-variable">$image</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">0</span></span><span>);

</span><span><span class="hljs-comment">// 绘制一个简单的矩形</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagerectangle</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>, </span><span><span class="hljs-number">10</span></span><span>, </span><span><span class="hljs-number">10</span></span><span>, </span><span><span class="hljs-number">90</span></span><span>, </span><span><span class="hljs-number">90</span></span><span>, </span><span><span class="hljs-variable">$black</span></span><span>);

</span><span><span class="hljs-comment">// 输出为 WBMP 格式</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagewbmp</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);

</span><span><span class="hljs-comment">// 释放内存</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

二、imagecopy函数简介

imagecopy 函数用于将一个图像的部分复制到另一个图像中。这对于在图像上叠加内容或从一个图像中提取区域并将其合并到另一个图像中非常有用。

语法：

<span><span><span class="hljs-keyword">bool</span></span><span> </span><span><span class="hljs-title function_ invoke__">imagecopy</span></span><span>(resource </span><span><span class="hljs-variable">$destination</span></span><span>, resource </span><span><span class="hljs-variable">$source</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$dst_x</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$dst_y</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$src_x</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$src_y</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$src_w</span></span><span>, </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$src_h</span></span><span>);
</span></span>

• $destination：目标图像资源。

• $source：源图像资源。

• $dst_x、$dst_y：目标图像的起始位置。

• $src_x、$src_y：源图像的起始位置。

• $src_w、$src_h：源图像的宽度和高度。

使用示例：

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 创建一个源图像</span></span><span>
</span><span><span class="hljs-variable">$source</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreatetruecolor</span></span><span>(</span><span><span class="hljs-number">100</span></span><span>, </span><span><span class="hljs-number">100</span></span><span>);
</span><span><span class="hljs-variable">$white</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecolorallocate</span></span><span>(</span><span><span class="hljs-variable">$source</span></span><span>, </span><span><span class="hljs-number">255</span></span><span>, </span><span><span class="hljs-number">255</span></span><span>, </span><span><span class="hljs-number">255</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">imagefill</span></span><span>(</span><span><span class="hljs-variable">$source</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-variable">$white</span></span><span>);

</span><span><span class="hljs-comment">// 在源图像上绘制一些内容</span></span><span>
</span><span><span class="hljs-variable">$black</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecolorallocate</span></span><span>(</span><span><span class="hljs-variable">$source</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">0</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">imageline</span></span><span>(</span><span><span class="hljs-variable">$source</span></span><span>, </span><span><span class="hljs-number">10</span></span><span>, </span><span><span class="hljs-number">10</span></span><span>, </span><span><span class="hljs-number">90</span></span><span>, </span><span><span class="hljs-number">90</span></span><span>, </span><span><span class="hljs-variable">$black</span></span><span>);

</span><span><span class="hljs-comment">// 创建一个目标图像</span></span><span>
</span><span><span class="hljs-variable">$destination</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreatetruecolor</span></span><span>(</span><span><span class="hljs-number">200</span></span><span>, </span><span><span class="hljs-number">200</span></span><span>);
</span><span><span class="hljs-variable">$bgColor</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecolorallocate</span></span><span>(</span><span><span class="hljs-variable">$destination</span></span><span>, </span><span><span class="hljs-number">255</span></span><span>, </span><span><span class="hljs-number">255</span></span><span>, </span><span><span class="hljs-number">255</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">imagefill</span></span><span>(</span><span><span class="hljs-variable">$destination</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-variable">$bgColor</span></span><span>);

</span><span><span class="hljs-title function_ invoke__">imagecopy</span></span><span>(</span><span><span class="hljs-variable">$destination</span></span><span>, </span><span><span class="hljs-variable">$source</span></span><span>, </span><span><span class="hljs-number">50</span></span><span>, </span><span><span class="hljs-number">50</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">100</span></span><span>, </span><span><span class="hljs-number">100</span></span><span>);

</span><span><span class="hljs-comment">// 输出图像到浏览器</span></span><span>
</span><span><span class="hljs-title function_ invoke__">header</span></span><span>(</span><span><span class="hljs-string">'Content-Type: image/png'</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">imagepng</span></span><span>(</span><span><span class="hljs-variable">$destination</span></span><span>);

</span><span><span class="hljs-comment">// 释放内存</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$source</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$destination</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

三、imagewbmp与imagecopy结合使用的实际案例

在本案例中，我们将演示如何利用 imagewbmp 和 imagecopy 函数结合起来，制作一个复杂的图像效果：将一个图像的部分区域叠加到另一个图像中，并输出为 WBMP 格式。假设我们有一个背景图像，并且想要将一个图标或其他图像的部分区域叠加到该背景图像上，然后输出为低质量的 WBMP 格式，以便适应移动设备。

案例步骤：

1. 加载背景图像和待叠加图像。

2. 使用 imagecopy 将待叠加图像的一部分复制到背景图像上。

3. 使用 imagewbmp 输出最终的图像。

实现代码：

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-comment">// 加载背景图像</span></span><span>
</span><span><span class="hljs-variable">$background</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreatefromjpeg</span></span><span>(</span><span><span class="hljs-string">'background.jpg'</span></span><span>);

</span><span><span class="hljs-comment">// 加载待叠加的图像</span></span><span>
</span><span><span class="hljs-variable">$overlay</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreatefrompng</span></span><span>(</span><span><span class="hljs-string">'overlay.png'</span></span><span>);

</span><span><span class="hljs-comment">// 获取待叠加图像的宽度和高度</span></span><span>
</span><span><span class="hljs-variable">$overlay_width</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagesx</span></span><span>(</span><span><span class="hljs-variable">$overlay</span></span><span>);
</span><span><span class="hljs-variable">$overlay_height</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagesy</span></span><span>(</span><span><span class="hljs-variable">$overlay</span></span><span>);

</span><span><span class="hljs-comment">// 选择待叠加图像的部分区域</span></span><span>
</span><span><span class="hljs-variable">$src_x</span></span><span> = </span><span><span class="hljs-number">0</span></span><span>;
</span><span><span class="hljs-variable">$src_y</span></span><span> = </span><span><span class="hljs-number">0</span></span><span>;
</span><span><span class="hljs-variable">$src_w</span></span><span> = </span><span><span class="hljs-variable">$overlay_width</span></span><span>;
</span><span><span class="hljs-variable">$src_h</span></span><span> = </span><span><span class="hljs-variable">$overlay_height</span></span><span>;

</span><span><span class="hljs-comment">// 在背景图像上选择叠加位置</span></span><span>
</span><span><span class="hljs-variable">$dst_x</span></span><span> = </span><span><span class="hljs-number">50</span></span><span>;
</span><span><span class="hljs-variable">$dst_y</span></span><span> = </span><span><span class="hljs-number">50</span></span><span>;

</span><span><span class="hljs-title function_ invoke__">imagecopy</span></span><span>(</span><span><span class="hljs-variable">$background</span></span><span>, </span><span><span class="hljs-variable">$overlay</span></span><span>, </span><span><span class="hljs-variable">$dst_x</span></span><span>, </span><span><span class="hljs-variable">$dst_y</span></span><span>, </span><span><span class="hljs-variable">$src_x</span></span><span>, </span><span><span class="hljs-variable">$src_y</span></span><span>, </span><span><span class="hljs-variable">$src_w</span></span><span>, </span><span><span class="hljs-variable">$src_h</span></span><span>);

</span><span><span class="hljs-comment">// 输出为WBMP格式</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagewbmp</span></span><span>(</span><span><span class="hljs-variable">$background</span></span><span>);

</span><span><span class="hljs-comment">// 释放内存</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$background</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$overlay</span></span><span>);
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

解释：

1. imagecreatefromjpeg 和 imagecreatefrompng 函数分别用于加载 JPEG 背景图像和 PNG 格式的叠加图像。

2. 使用 imagecopy 函数将叠加图像的一部分（从 (0, 0) 开始，宽度和高度为叠加图像的大小）复制到背景图像的 (50, 50) 位置。

3. 最后，使用 imagewbmp 将处理后的图像输出为 WBMP 格式，适合低带宽或移动设备使用。

四、总结

通过将 imagewbmp 和 imagecopy 函数结合使用，我们可以实现复杂的图像叠加效果，并且将最终图像转换为适合移动设备或低带宽环境的 WBMP 格式。这种方法在动态生成图像或为用户提供个性化内容时非常有用，特别是在开发需要支持老式移动设备或特定图像格式的应用时。

希望这个案例能够帮助你更好地理解如何在 PHP 中利用这两个函数实现复杂的图像效果。