php如何实现网站的图片压缩


php如何实现网站的图片压缩

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我们经常会用到把上传的大图片压缩,特别是体积,在微信等App应用上,也默认都是有压缩的,那么,怎么样对图片大幅度压缩却仍能保持较高的清晰度呢?
压缩通常是有按比例缩放,和指定宽度压缩的,效果很不错,一个数码相机拍的4M图片,压缩后保持了较高的清晰度和原图宽高值,只有700K 。
【php如何实现网站的图片压缩】下面是代码(有两个文件,imgcompress.class.php%20类,及compress.php)
1、创建一个imgcompress类,imgcompress.class.php
<?php/***%20图片压缩类:通过缩放来压缩 。*%20如果要保持源图比例,把参数$percent保持为即可 。*%20即使原比例压缩,也可大幅度缩小 。数码相机M图片 。也可以缩为KB左右 。如果缩小比例,则体积会更小 。**%20结果:可保存、可直接显示 。*/class%20imgcompress{private%20$src;private%20$image;private%20$imageinfo;private%20$percent%20=%20.;/***%20图片压缩*%20@param%20$src%20源图*%20@param%20float%20$percent%20压缩比例*/public%20function%20__construct($src,%20$percent=){$this->src%20=%20$src;$this->percent%20=%20$percent;}/**%20高清压缩图片*%20@param%20string%20$saveName%20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%20function%20compressImg($saveName=''){$this->_openImage();if(!empty($saveName))%20$this->_saveImage($saveName);%20//保存else%20$this->_showImage();}/***%20内部:打开图片*/private%20function%20_openImage(){list($width,%20$height,%20$type,%20$attr)%20=%20getimagesize($this->src);$this->imageinfo%20=%20array('width'=>$width,'height'=>$height,'type'=>image_type_to_extension($type,false),'attr'=>$attr);$fun%20=%20"imagecreatefrom".$this->imageinfo['type'];$this->image%20=%20$fun($this->src);$this->_thumpImage();}/***%20内部:操作图片*/private%20function%20_thumpImage(){$new_width%20=%20$this->imageinfo['width']%20*%20$this->percent;$new_height%20=%20$this->imageinfo['height']%20*%20$this->percent;$image_thump%20=%20imagecreatetruecolor($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['width'],$this->imageinfo['height']);imagedestroy($this->image);$this->image%20=%20$image_thump;}/***%20输出图片:保存图片则用saveImage()*/private%20function%20_showImage(){header('Content-Type:%20image/'.$this->imageinfo['type']);$funcs%20=%20"image".$this->imageinfo['type'];$funcs($this->image);}/***%20保存图片到硬盘:*%20@param%20string%20$dstImgName%20、可指定字符串不带后缀的名称,使用源图扩展名%20 。、直接指定目标图片名带扩展名 。*/private%20function%20_saveImage($dstImgName){if(empty($dstImgName))%20return%20false;$allowImgs%20=%20['.jpg', '.jpeg', '.png', '.bmp', '.wbmp','.gif']; //如果目标图片名有后缀就用目标图片扩展名 后缀,如果没有,则用源图的扩展名$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['type'];}$funcs = "image".$this->imageinfo['type'];$funcs($this->image,$dstName);}/*** 销毁图片*/public function __destruct(){imagedestroy($this->image);}}2、使用,compress.php
<?phprequire_once 'imgcompress.class.php';$source = 'test.png';//原图文件名$dst_img = 'test_.png';//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);使用之后个人感觉 $percent 设置为0.5 左右就不错了,压缩后的图片与原图质量基本一样 。
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