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如何利用php把上传的图片压缩?

如图。是用post提交的图片,上传的sae数据库,怎么才能把图片压小一点,一张图几m实在受不了

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小旋风柴进 2016-03-09 09:09:44 4011 0
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  • PHP压缩图片两个步骤:
    1、添加类

    //php生成缩略图片的类
    
    class ResizeImage{
    
        public $type;//图片类型
    
        public $width;//实际宽度
    
        public $height;//实际高度
    
        public $resize_width;//改变后的宽度
    
        public $resize_height;//改变后的高度
    
        public $cut;//是否裁图
    
        public $srcimg;//源图象 
    
        public $dstimg;//目标图象地址
    
        public $im;//临时创建的图象
    
        public $quality;//图片质量
    
        public $img_array=array('jpg','png','gif');
    
        //http://www.phpernote.com/php-function/782.html
    
        function __construct($img,$wid,$hei,$c,$dstpath,$quality=100){
    
            $this->srcimg=$img;
    
            $this->resize_width=$wid;
    
            $this->resize_height=$hei;
    
            $this->cut=$c;
    
            $this->quality=$quality;
    
            //$this->type=strtolower(substr(strrchr($this->srcimg,'.'),1));//图片的类型
    
            $this->type=$this->checkFileType($this->srcimg);//更为严格的检测图片类型
    
            if(!in_array($this->type,$this->img_array)){
    
                return '';
    
            }
    
            $this->initi_img();//初始化图象
    
            $this -> dst_img($dstpath);//目标图象地址
    
            $this->width=imagesx($this->im);
    
            $this->height=imagesy($this->im);
    
            $this->newimg();//生成图象
    
            ImageDestroy($this->im);
    
        }
    
        function newimg(){
    
            $resize_ratio=($this->resize_width)/($this->resize_height);//改变后的图象的比例
    
            $ratio=($this->width)/($this->height);//实际图象的比例
    
            if(($this->cut)=='1'){//裁图
    
                if(function_exists('imagepng')&&(str_replace('.','',PHP_VERSION)>=512)){//针对php版本大于5.12参数变化后的处理情况
    
                    $quality=9;
    
                }
    
                if($ratio>=$resize_ratio){//高度优先
    
                    $newimg=imagecreatetruecolor($this->resize_width,$this->resize_height);
    
                    //上色 
                    $color=imagecolorallocate($newimg,255,255,255); 
                    //设置透明 
                    imagecolortransparent($newimg,$color); 
                    imagefill($newimg,0,0,$color); 
    
                    imagecopyresampled($newimg,$this->im,0,0,0,0,$this->resize_width,$this->resize_height,(($this->height)*$resize_ratio),$this->height);
    
                    imagejpeg($newimg,$this->dstimg,$this->quality);
    
                }
    
                if($ratio<$resize_ratio){//宽度优先
    
                    $newimg=imagecreatetruecolor($this->resize_width,$this->resize_height);
    
                    //上色 
                    $color=imagecolorallocate($newimg,255,255,255); 
                    //设置透明 
                    imagecolortransparent($newimg,$color); 
                    imagefill($newimg,0,0,$color); 
    
                    imagecopyresampled($newimg,$this->im,0,0,0,0,$this->resize_width,$this->resize_height,$this->width,(($this->width)/$resize_ratio));
    
                    imagejpeg($newimg,$this->dstimg,$this->quality);
    
                }
    
            }else{//不裁图
    
                if($ratio>=$resize_ratio){
    
                    $newimg=imagecreatetruecolor($this->resize_width,($this->resize_width)/$ratio);
    
                    //上色 
                    $color=imagecolorallocate($newimg,255,255,255); 
                    //设置透明 
                    imagecolortransparent($newimg,$color); 
                    imagefill($newimg,0,0,$color); 
    
                    imagecopyresampled($newimg,$this->im,0,0,0,0,$this->resize_width,($this->resize_width)/$ratio,$this->width,$this->height);
    
                    imagejpeg($newimg,$this->dstimg,$this->quality);
    
                }
    
                if($ratio<$resize_ratio){
    
                    $newimg=imagecreatetruecolor(($this->resize_height)*$ratio,$this->resize_height);
    
                    //上色 
                    $color=imagecolorallocate($newimg,255,255,255); 
                    //设置透明 
                    imagecolortransparent($newimg,$color); 
                    imagefill($newimg,0,0,$color); 
    
                    imagecopyresampled($newimg,$this->im,0,0,0,0,($this->resize_height)*$ratio,$this->resize_height,$this->width,$this->height);
    
                    imagejpeg($newimg,$this->dstimg,$this->quality);
    
                }
    
            }
    
        }
    
        function initi_img(){//初始化图象
    
            if($this->type=='jpg'){
    
                $this->im=imagecreatefromjpeg($this->srcimg);
    
            }
    
            if($this->type=='gif'){
    
                $this->im=imagecreatefromgif($this->srcimg);
    
            }
    
            if($this->type=='png'){
    
                $this->im=imagecreatefrompng($this->srcimg);
    
            }
    
        }
    
        function dst_img($dstpath){//图象目标地址
    
            $full_length=strlen($this->srcimg);
    
            $type_length=strlen($this->type);
    
            $name_length=$full_length-$type_length;
    
            $name=substr($this->srcimg,0,$name_length-1);
    
            $this->dstimg=$dstpath;
    
            //echo $this->dstimg;
    
        }
    
        //读取文件前几个字节 判断文件类型
    
        function checkFileType($filename){
    
            $file=fopen($filename,'rb');
    
            $bin=fread($file,2); //只读2字节
    
            fclose($file);
    
            $strInfo =@unpack("c2chars",$bin);
    
            $typeCode=intval($strInfo['chars1'].$strInfo['chars2']);
    
            $fileType='';
    
            switch($typeCode){
    
                case 7790:
    
                    $fileType='exe';
    
                break;
    
                case 7784:
    
                    $fileType='midi';
    
                break;
    
                case 8297:
    
                    $fileType='rar';
    
                break;
    
                case 255216:
    
                    $fileType='jpg';
    
                break;
    
                case 7173:
    
                    $fileType='gif';
    
                break;
    
                case 6677:
    
                    $fileType='bmp';
    
                break;
    
                case 13780:
    
                    $fileType='png';
    
                break;
    
                default:
    
                    $fileType='unknown'.$typeCode;
    
                break;
    
            }
    
            if($strInfo['chars1']=='-1'&&$strInfo['chars2']=='-40'){
    
                return 'jpg';
    
            }
    
            if($strInfo['chars1']=='-119'&&$strInfo['chars2']=='80'){
    
                return 'png';
    
            }
    
            return $fileType;
    
        }
    
    }

    2、压缩图片

    $resizeimage=new ResizeImage($file_path,300,169,0,$newname);

    ResizeImage会将你正在上传的图片压缩至相应尺寸,同时上传。参数意义(路径, width, height, 是否截图, 图片名称),$file_path的根目录是这个php所在的文件夹,可以修改调整至相应路径。
    通过该方法,成功将900+kb的图片压缩至40+kb,图片加载迅速很多。

    2019-07-17 18:55:18
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