How to implement image compression for websites in php

phpHow to realize website image compression

We often use it to compress uploaded large images, especially It’s the volume. In APP applications such as WeChat, compression is also provided by default. So, how to greatly compress images while still maintaining high definition?

Compression is usually proportional The effect of scaling and compressing the specified width is very good. A 4M picture taken by a digital camera maintains a high definition and the original image width and height after compression, only 700K.

The following is the code (there are two files, imgcompress.class.php class, and compress.php)

1. Create an imgcompress class, imgcompress.class.php

<?php
/**
* 图片压缩类：通过缩放来压缩。
* 如果要保持源图比例，把参数$percent保持为即可。
* 即使原比例压缩，也可大幅度缩小。数码相机M图片。也可以缩为KB左右。如果缩小比例，则体积会更小。
*
* 结果：可保存、可直接显示。
*/
class imgcompress{
private $src;
private $image;
private $imageinfo;
private $percent = .;
/**
* 图片压缩
* @param $src 源图
* @param float $percent 压缩比例
*/
public function __construct($src, $percent=)
{
$this->src = $src;
$this->percent = $percent;
}
/** 高清压缩图片
* @param string $saveName 提供图片名（可不带扩展名，用源图扩展名）用于保存。或不提供文件名直接显示
*/
public function compressImg($saveName=&#39;&#39;)
{
$this->_openImage();
if(!empty($saveName)) $this->_saveImage($saveName); //保存
else $this->_showImage();
}
/**
* 内部：打开图片
*/
private function _openImage()
{
list($width, $height, $type, $attr) = getimagesize($this->src);
$this->imageinfo = array(
&#39;width&#39;=>$width,
&#39;height&#39;=>$height,
&#39;type&#39;=>image_type_to_extension($type,false),
&#39;attr&#39;=>$attr
);
$fun = "imagecreatefrom".$this->imageinfo[&#39;type&#39;];
$this->image = $fun($this->src);
$this->_thumpImage();
}
/**
* 内部：操作图片
*/
private function _thumpImage()
{
$new_width = $this->imageinfo[&#39;width&#39;] * $this->percent;
$new_height = $this->imageinfo[&#39;height&#39;] * $this->percent;
$image_thump = imagecreatetruecolor($new_width,$new_height);
//将原图复制带图片载体上面，并且按照一定比例压缩,极大的保持了清晰度
imagecopyresampled($image_thump,$this->image,,,,,$new_width,$new_height,$this->imageinfo[&#39;width&#39;],$this->imageinfo[&#39;height&#39;]);
imagedestroy($this->image);
$this->image = $image_thump;
}
/**
* 输出图片:保存图片则用saveImage()
*/
private function _showImage()
{
header(&#39;Content-Type: image/&#39;.$this->imageinfo[&#39;type&#39;]);
$funcs = "image".$this->imageinfo[&#39;type&#39;];
$funcs($this->image);
}
/**
* 保存图片到硬盘：
* @param string $dstImgName 、可指定字符串不带后缀的名称，使用源图扩展名 。、直接指定目标图片名带扩展名。
*/
private function _saveImage($dstImgName)
{
if(empty($dstImgName)) return false;
$allowImgs = [&#39;.jpg&#39;, &#39;.jpeg&#39;, &#39;.png&#39;, &#39;.bmp&#39;, &#39;.wbmp&#39;,&#39;.gif&#39;]; //如果目标图片名有后缀就用目标图片扩展名 后缀，如果没有，则用源图的扩展名
$dstExt = strrchr($dstImgName ,".");
$sourseExt = strrchr($this->src ,".");
if(!empty($dstExt)) $dstExt =strtolower($dstExt);
if(!empty($sourseExt)) $sourseExt =strtolower($sourseExt);
//有指定目标名扩展名
if(!empty($dstExt) && in_array($dstExt,$allowImgs)){
$dstName = $dstImgName;
}elseif(!empty($sourseExt) && in_array($sourseExt,$allowImgs)){
$dstName = $dstImgName.$sourseExt;
}else{
$dstName = $dstImgName.$this->imageinfo[&#39;type&#39;];
}
$funcs = "image".$this->imageinfo[&#39;type&#39;];
$funcs($this->image,$dstName);
}
/**
* 销毁图片
*/
public function __destruct(){
imagedestroy($this->image);
}
}

2. Use, compress.php

<?php
require_once &#39;imgcompress.class.php&#39;;
$source = &#39;test.png&#39;;//原图文件名
$dst_img = &#39;test_.png&#39;;//保存图片的文件名
$percent = ; #原图压缩，不缩放，但体积大大降低
$image = (new imgcompress($source,$percent))->compressImg($dst_img);

My personal feeling after using it $percent Set to 0.5 or so. The quality of the compressed image is basically the same as the original image.

For more PHP related knowledge, please visit PHP Chinese website!

The above is the detailed content of How to implement image compression for websites in php. For more information, please follow other related articles on the PHP Chinese website!