Note: This function depends on the GD2 graphics library
I recently wanted to use PHP to generate thumbnails. I searched online and found this article: Generate image thumbnails with PHP
After trying it out, I found the following problems:
1. The thumbnails generated from png images are in jpg format.
2. The thumbnail generated from the png image has no transparent (semi-transparent) effect (filled with black background)
3. The code syntax is relatively old
Therefore, we simply modified and optimized it based on this version.
PHP generate thumbnail class
<?<span>php </span><span>/*</span><span> * desc: Resize Image(png, jpg, gif)
* author: 十年后的卢哥哥(http://www.cnblogs.com/lurenjiashuo/)
* date: 2014.11.13
* base from: http://www.oschina.net/code/snippet_5189_2491 </span><span>*/</span><span>class</span><span> ResizeImage { </span><span>//</span><span>图片类型</span><span>private</span><span>$type</span><span>; </span><span>//</span><span>实际宽度</span><span>private</span><span>$width</span><span>; </span><span>//</span><span>实际高度</span><span>private</span><span>$height</span><span>; </span><span>//</span><span>改变后的宽度</span><span>private</span><span>$resize_width</span><span>; </span><span>//</span><span>改变后的高度</span><span>private</span><span>$resize_height</span><span>; </span><span>//</span><span>是否裁图</span><span>private</span><span>$cut</span><span>; </span><span>//</span><span>源图象</span><span>private</span><span>$srcimg</span><span>; </span><span>//</span><span>目标图象地址</span><span>private</span><span>$dstimg</span><span>; </span><span>//</span><span>临时创建的图象</span><span>private</span><span>$im</span><span>; </span><span>function</span> __construct(<span>$imgPath</span>, <span>$width</span>, <span>$height</span>, <span>$isCut</span>, <span>$savePath</span><span>) { </span><span>$this</span>->srcimg = <span>$imgPath</span><span>; </span><span>$this</span>->resize_width = <span>$width</span><span>; </span><span>$this</span>->resize_height = <span>$height</span><span>; </span><span>$this</span>->cut = <span>$isCut</span><span>; </span><span>//</span><span>图片的类型</span><span>$this</span>->type = <span>strtolower</span>(<span>substr</span>(<span>strrchr</span>(<span>$this</span>->srcimg,"."),1<span>)); </span><span>//</span><span>初始化图象</span><span>$this</span>-><span>initi_img(); </span><span>//</span><span>目标图象地址</span><span>$this</span> -> dst_img(<span>$savePath</span><span>); </span><span>//</span><span>--</span><span>$this</span>->width = imagesx(<span>$this</span>-><span>im); </span><span>$this</span>->height = imagesy(<span>$this</span>-><span>im); </span><span>//</span><span>生成图象</span><span>$this</span>-><span>newimg();
ImageDestroy (</span><span>$this</span>-><span>im);
} </span><span>private</span><span>function</span><span> newimg() { </span><span>//</span><span>改变后的图象的比例</span><span>$resize_ratio</span> = (<span>$this</span>->resize_width)/(<span>$this</span>-><span>resize_height); </span><span>//</span><span>实际图象的比例</span><span>$ratio</span> = (<span>$this</span>->width)/(<span>$this</span>-><span>height); </span><span>if</span>(<span>$this</span>-><span>cut) { </span><span>//</span><span>裁图</span><span>$newimg</span> = imagecreatetruecolor(<span>$this</span>->resize_width,<span>$this</span>-><span>resize_height); </span><span>if</span>(<span>$this</span>->type=="png"<span>) {
imagefill(</span><span>$newimg</span>, 0, 0, imagecolorallocatealpha(<span>$newimg</span>, 0, 0, 0, 127<span>));
} </span><span>if</span>(<span>$ratio</span>>=<span>$resize_ratio</span><span>) { </span><span>//</span><span>高度优先</span> imagecopyresampled(<span>$newimg</span>, <span>$this</span>->im, 0, 0, 0, 0, <span>$this</span>->resize_width,<span>$this</span>->resize_height, ((<span>$this</span>->height)*<span>$resize_ratio</span>), <span>$this</span>-><span>height);
} </span><span>else</span><span> { </span><span>//</span><span>宽度优先</span> imagecopyresampled(<span>$newimg</span>, <span>$this</span>->im, 0, 0, 0, 0, <span>$this</span>->resize_width, <span>$this</span>->resize_height, <span>$this</span>->width, ((<span>$this</span>->width)/<span>$resize_ratio</span><span>));
}
} </span><span>else</span><span> { </span><span>//</span><span>不裁图</span><span>if</span>(<span>$ratio</span>>=<span>$resize_ratio</span><span>) { </span><span>$newimg</span> = imagecreatetruecolor(<span>$this</span>->resize_width,(<span>$this</span>->resize_width)/<span>$ratio</span><span>); </span><span>if</span>(<span>$this</span>->type=="png"<span>) {
imagefill(</span><span>$newimg</span>, 0, 0, imagecolorallocatealpha(<span>$newimg</span>, 0, 0, 0, 127<span>));
}
imagecopyresampled(</span><span>$newimg</span>, <span>$this</span>->im, 0, 0, 0, 0, <span>$this</span>->resize_width, (<span>$this</span>->resize_width)/<span>$ratio</span>, <span>$this</span>->width, <span>$this</span>-><span>height);
} </span><span>else</span><span> { </span><span>$newimg</span> = imagecreatetruecolor((<span>$this</span>->resize_height)*<span>$ratio</span>,<span>$this</span>-><span>resize_height); </span><span>if</span>(<span>$this</span>->type=="png"<span>) {
imagefill(</span><span>$newimg</span>, 0, 0, imagecolorallocatealpha(<span>$newimg</span>, 0, 0, 0, 127<span>));
}
imagecopyresampled(</span><span>$newimg</span>, <span>$this</span>->im, 0, 0, 0, 0, (<span>$this</span>->resize_height)*<span>$ratio</span>, <span>$this</span>->resize_height, <span>$this</span>->width, <span>$this</span>-><span>height);
}
} </span><span>if</span>(<span>$this</span>->type=="png"<span>) {
imagesavealpha(</span><span>$newimg</span>, <span>true</span><span>);
imagepng (</span><span>$newimg</span>,<span>$this</span>-><span>dstimg);
} </span><span>else</span><span> {
imagejpeg (</span><span>$newimg</span>,<span>$this</span>-><span>dstimg);
}
} </span><span>//</span><span>初始化图象</span><span>private</span><span>function</span><span> initi_img() { </span><span>if</span>(<span>$this</span>->type=="jpg"<span>) { </span><span>$this</span>->im = imagecreatefromjpeg(<span>$this</span>-><span>srcimg);
} </span><span>if</span>(<span>$this</span>->type=="gif"<span>) { </span><span>$this</span>->im = imagecreatefromgif(<span>$this</span>-><span>srcimg);
} </span><span>if</span>(<span>$this</span>->type=="png"<span>) { </span><span>$this</span>->im = imagecreatefrompng(<span>$this</span>-><span>srcimg);
}
} </span><span>//</span><span>图象目标地址</span><span>private</span><span>function</span> dst_img(<span>$dstpath</span><span>) { </span><span>$full_length</span> = <span>strlen</span>(<span>$this</span>-><span>srcimg); </span><span>$type_length</span> = <span>strlen</span>(<span>$this</span>-><span>type); </span><span>$name_length</span> = <span>$full_length</span>-<span>$type_length</span><span>; </span><span>$name</span> = <span>substr</span>(<span>$this</span>->srcimg,0,<span>$name_length</span>-1<span>); </span><span>$this</span>->dstimg = <span>$dstpath</span><span>;
}
} </span>?>Copy after login
use
When using it, just call the constructor of the class directly. The constructor is as follows:
<span>$resizeimage</span> = <span>new</span> resizeimage($imgPath, $width, $height, $isCut, $savePath);
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parameters
$imgPath: original image address
$width: thumbnail width
$height: Thumbnail height
$isCut: Whether to crop, bool value
$savePath: thumbnail address (can be the same as the original image address)
Example
<?<span>php </span><span>include</span> "ResizeImage.php"<span>; </span><span>//</span><span>jpg</span><span>$jpgResize</span> = <span>new</span> ResizeImage("img/test_1920_1200.jpg", 320, 240, <span>false</span>, "img/test_320_240.jpg"<span>); </span><span>//</span><span>png</span><span>$pngResize</span> = <span>new</span> ResizeImage("img/test_1024_746.png", 320, 240, <span>false</span>, "img/test_320_240.png"<span>); </span>?>Copy after login
Effect
The above introduces how PHP generates transparent png image thumbnails, including the content of generating thumbnails in PHP. I hope it will be helpful to friends who are interested in PHP tutorials.
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