中文(繁體)
中文(繁體)
在PHP 中， imagecreatefrompng()函數是用於創建一個圖像資源（GD 圖像資源）從PNG 格式的圖像文件。這個函數對於處理圖像文件非常常見，尤其是在涉及動態圖像生成、圖像處理或圖像編輯時。但是，很多開發者在使用imagecreatefrompng()創建圖像資源之後，往往需要獲取圖像的寬度和高度來做進一步處理。
本文將詳細介紹如何在使用imagecreatefrompng()函數時，讀取和處理圖像的寬度和高度。
PHP 提供了imagesx()和imagesy()這兩個函數來獲取圖像資源的寬度和高度。通過這兩個函數，我們可以在調用imagecreatefrompng()創建圖像資源後，獲取該圖像的具體尺寸。
<span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// 載入 PNG 圖像文件</span></span><span>
</span><span><span class="hljs-variable">$image</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreatefrompng</span></span><span>(</span><span><span class="hljs-string">'path/to/your/image.png'</span></span><span>);
</span><span><span class="hljs-comment">// 獲取圖像的寬度</span></span><span>
</span><span><span class="hljs-variable">$width</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagesx</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);
</span><span><span class="hljs-comment">// 獲取圖像的高度</span></span><span>
</span><span><span class="hljs-variable">$height</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagesy</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);
</span><span><span class="hljs-comment">// 輸出圖像的寬度和高度</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"圖像的寬度為: "</span></span><span> . </span><span><span class="hljs-variable">$width</span></span><span> . </span><span><span class="hljs-string">" 像素\n"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"圖像的高度為: "</span></span><span> . </span><span><span class="hljs-variable">$height</span></span><span> . </span><span><span class="hljs-string">" 像素\n"</span></span><span>;
</span><span><span class="hljs-comment">// 銷毀圖像資源</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);
</span><span><span class="hljs-meta">?></span></span><span>
</span></span>在這個示例中，首先使用imagecreatefrompng()函數加載圖像文件，然後通過imagesx()獲取圖像的寬度，通過imagesy()獲取圖像的高度。最後，將圖像的寬度和高度輸出到瀏覽器。
除了使用imagesx()和imagesy()外，我們還可以使用getimagesize()函數來獲取圖像的寬度和高度。 getimagesize()不僅返回圖像的尺寸，還會返回更多的圖像信息，包括圖像的MIME 類型等。這對於需要處理文件信息的場景非常有用。
<span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// 使用 getimagesize() 獲取圖像的寬度和高度</span></span><span>
</span><span><span class="hljs-variable">$image_info</span></span><span> = </span><span><span class="hljs-title function_ invoke__">getimagesize</span></span><span>(</span><span><span class="hljs-string">'path/to/your/image.png'</span></span><span>);
</span><span><span class="hljs-comment">// 獲取圖像的寬度</span></span><span>
</span><span><span class="hljs-variable">$width</span></span><span> = </span><span><span class="hljs-variable">$image_info</span></span><span>[</span><span><span class="hljs-number">0</span></span><span>];
</span><span><span class="hljs-comment">// 獲取圖像的高度</span></span><span>
</span><span><span class="hljs-variable">$height</span></span><span> = </span><span><span class="hljs-variable">$image_info</span></span><span>[</span><span><span class="hljs-number">1</span></span><span>];
</span><span><span class="hljs-comment">// 輸出圖像的寬度和高度</span></span><span>
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"圖像的寬度為: "</span></span><span> . </span><span><span class="hljs-variable">$width</span></span><span> . </span><span><span class="hljs-string">" 像素\n"</span></span><span>;
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"圖像的高度為: "</span></span><span> . </span><span><span class="hljs-variable">$height</span></span><span> . </span><span><span class="hljs-string">" 像素\n"</span></span><span>;
</span><span><span class="hljs-meta">?></span></span><span>
</span></span>在這裡， getimagesize()返回的是一個數組，數組的第一個元素（ $image_info[0] ）是圖像的寬度，第二個元素（ $image_info[1] ）是圖像的高度。
在許多圖像處理的場景中，我們可能需要根據圖像的寬高進行某些處理。例如，調整圖像的尺寸、裁剪圖像等。通過獲取圖像的寬度和高度，我們可以實現這些功能。
如果我們需要將圖像縮放到指定的寬度和高度，可以使用imagecopyresampled()函數。
<span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// 載入圖像文件</span></span><span>
</span><span><span class="hljs-variable">$image</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreatefrompng</span></span><span>(</span><span><span class="hljs-string">'path/to/your/image.png'</span></span><span>);
</span><span><span class="hljs-comment">// 獲取原圖的寬度和高度</span></span><span>
</span><span><span class="hljs-variable">$width</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagesx</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);
</span><span><span class="hljs-variable">$height</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagesy</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);
</span><span><span class="hljs-comment">// 設置新的寬度和高度</span></span><span>
</span><span><span class="hljs-variable">$new_width</span></span><span> = </span><span><span class="hljs-number">200</span></span><span>;
</span><span><span class="hljs-variable">$new_height</span></span><span> = </span><span><span class="hljs-number">150</span></span><span>;
</span><span><span class="hljs-comment">// 創建一個新的空白圖像</span></span><span>
</span><span><span class="hljs-variable">$new_image</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreatetruecolor</span></span><span>(</span><span><span class="hljs-variable">$new_width</span></span><span>, </span><span><span class="hljs-variable">$new_height</span></span><span>);
</span><span><span class="hljs-comment">// 使用 imagecopyresampled() 進行圖像縮放</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagecopyresampled</span></span><span>(</span><span><span class="hljs-variable">$new_image</span></span><span>, </span><span><span class="hljs-variable">$image</span></span><span>, </span><span><span class="hljs-number">0</span></span><span>, </span><span><span class="hljs-number">0</span></span><span>, </span><span><span class="hljs-number">0</span></span><span>, </span><span><span class="hljs-number">0</span></span><span>, </span><span><span class="hljs-variable">$new_width</span></span><span>, </span><span><span class="hljs-variable">$new_height</span></span><span>, </span><span><span class="hljs-variable">$width</span></span><span>, </span><span><span class="hljs-variable">$height</span></span><span>);
</span><span><span class="hljs-comment">// 輸出縮放後的圖像</span></span><span>
</span><span><span class="hljs-title function_ invoke__">header</span></span><span>(</span><span><span class="hljs-string">'Content-Type: image/png'</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">imagepng</span></span><span>(</span><span><span class="hljs-variable">$new_image</span></span><span>);
</span><span><span class="hljs-comment">// 銷毀圖像資源</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$new_image</span></span><span>);
</span><span><span class="hljs-meta">?></span></span><span>
</span></span>在這個例子中，我們加載了一個PNG 圖像，獲取了它的寬高，並使用imagecopyresampled()函數將其縮放為指定的200x150 的尺寸。最後，我們通過imagepng()輸出縮放後的圖像。
如果我們想從圖像中裁剪出某一部分，也可以根據寬度和高度進行相應的操作。
<span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-comment">// 載入圖像文件</span></span><span>
</span><span><span class="hljs-variable">$image</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreatefrompng</span></span><span>(</span><span><span class="hljs-string">'path/to/your/image.png'</span></span><span>);
</span><span><span class="hljs-comment">// 獲取圖像的寬度和高度</span></span><span>
</span><span><span class="hljs-variable">$width</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagesx</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);
</span><span><span class="hljs-variable">$height</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagesy</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);
</span><span><span class="hljs-comment">// 設置裁剪區域的坐標和尺寸</span></span><span>
</span><span><span class="hljs-variable">$x</span></span><span> = </span><span><span class="hljs-number">50</span></span><span>; </span><span><span class="hljs-comment">// 起始橫坐標</span></span><span>
</span><span><span class="hljs-variable">$y</span></span><span> = </span><span><span class="hljs-number">50</span></span><span>; </span><span><span class="hljs-comment">// 起始縱坐標</span></span><span>
</span><span><span class="hljs-variable">$crop_width</span></span><span> = </span><span><span class="hljs-number">100</span></span><span>;
</span><span><span class="hljs-variable">$crop_height</span></span><span> = </span><span><span class="hljs-number">100</span></span><span>;
</span><span><span class="hljs-comment">// 創建一個新的空白圖像</span></span><span>
</span><span><span class="hljs-variable">$cropped_image</span></span><span> = </span><span><span class="hljs-title function_ invoke__">imagecreatetruecolor</span></span><span>(</span><span><span class="hljs-variable">$crop_width</span></span><span>, </span><span><span class="hljs-variable">$crop_height</span></span><span>);
</span><span><span class="hljs-comment">// 使用 imagecopy() 進行裁剪</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagecopy</span></span><span>(</span><span><span class="hljs-variable">$cropped_image</span></span><span>, </span><span><span class="hljs-variable">$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">$x</span></span><span>, </span><span><span class="hljs-variable">$y</span></span><span>, </span><span><span class="hljs-variable">$crop_width</span></span><span>, </span><span><span class="hljs-variable">$crop_height</span></span><span>);
</span><span><span class="hljs-comment">// 輸出裁剪後的圖像</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">$cropped_image</span></span><span>);
</span><span><span class="hljs-comment">// 銷毀圖像資源</span></span><span>
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$image</span></span><span>);
</span><span><span class="hljs-title function_ invoke__">imagedestroy</span></span><span>(</span><span><span class="hljs-variable">$cropped_image</span></span><span>);
</span><span><span class="hljs-meta">?></span></span><span>
</span></span>在這個示例中，我們從圖像中裁剪出從坐標(50, 50)開始，尺寸為100x100 的區域，並將裁剪後的圖像輸出。
使用imagecreatefrompng()加載圖像文件後，獲取圖像的寬度和高度是圖像處理中的基本需求。我們可以通過imagesx()和imagesy()函數直接獲取圖像的寬高，或者使用getimagesize()獲取圖像的更多信息。在圖像處理的實際應用中，寬高值常常用於調整尺寸、裁剪圖像等操作，從而達到所需的效果。
以上是處理PNG 圖像時讀取寬度和高度的基本方法和技巧，了解這些函數後，你可以在PHP 中更好地進行圖像處理。
