【PHP縮略圖類】手機照片不能生成縮略圖問題以及解決方案

【本文原創(chuàng)，謝絕轉(zhuǎn)載】

一、出現(xiàn)的問題

這幾天做了手機上傳照片并裁出縮略圖的接口的測試，發(fā)現(xiàn)不管怎么，生成的縮略圖都是一片漆黑。:-(

然后就把這個縮略圖類單拿出來進行測試，發(fā)現(xiàn)只要是手機拍出來的照片都不能進行縮略圖的處理。。。。

二、問題分析以及解決方案

經(jīng)過群里的請教，發(fā)現(xiàn)問題可能是出現(xiàn)在文件的類型的判斷上，因為png圖片自帶一個透明的圖層，導(dǎo)致不能直接轉(zhuǎn)換成jpg的文件，而手機排出的照片擴展名是jpg.

所以，得出的結(jié)論是手機拍出的是jpg擴展名的png圖片。

由于擴展名是可以隨意修改的，不是很能保證文件的信息的準確性，所以我們采用了 getimagesize 函數(shù)進行文件類型的獲取。

//獲取真實的圖片類型 list($width, $height, $type, $attr) = getimagesize($this->sur_file);    switch($type) {          case 1 :              $img_type = 'gif';              break;          case 2 :              $img_type = 'jpeg';              break;          case 3 :              $img_type = 'png';              break;          case 15 :              $img_type = 'wbmp';              break;          default :              return false;      }  

三、生成縮略圖類

下面把修改后的生成縮略圖的類貼出來，供大家指正~

/** * php生成縮略圖類 * 修改者 點點細雨  * 文章出處 ： http://blog.csdn.net/diandianxiyu_geek * 2014-07-23 解決了圖片類型不能正常識別的問題 */class thumb {    public $sur_file; //讀取的原圖片    public $des_file; //生成目標圖片    public $tem_file; //臨時圖片    public $tag;  //縮略標簽  0,默認,按固定的高寬生成  1,按比列或固定最大長度生成  -1,按某個寬度或某個高度縮小    public $resize_width;  //$tag為0時,目標文件寬    public $resize_height;  //$tag為0時,目標文件高    public $sca_max; //$tag為1時,1時為最大長度(高或?qū)捴械淖畲笾?    public $type;  //圖片類型    public $width;  //原圖片寬    public $height;  //原圖片高    public $size;     //原圖大小    //構(gòu)造函數(shù)    public function __construct($surpic, $reswid, $reshei, $despic, $mark, $scamax) {        $this->sur_file = $surpic;        $this->resize_width = $reswid;        $this->resize_height = $reshei;        $this->tag = $mark;        $this->sca_max = $scamax;        list($width, $height, $type, $attr) = getimagesize($this->sur_file);        switch ($type) {            case 1 :                $img_type = 'gif';                break;            case 2 :                $img_type = 'jpeg';                break;            case 3 :                $img_type = 'png';                break;            case 15 :                $img_type = 'wbmp';                break;            default :                return false;        }        $this->type = $img_type; //獲取圖片類型        $this->init_img(); //初始化圖片        $this->des_file = $despic; //目標圖片地址        $this->width = $width;        $this->height = $height;        $this->size = filesize($surpic);        $this->new_img();        imagedestroy($this->tem_file);    }    //圖片初始化函數(shù)    private function init_img() {        if ($this->type == 'jpeg') {            $this->tem_file = imagecreatefromjpeg($this->sur_file);        } elseif ($this->type == 'jpg') {            $this->tem_file = imagecreatefromjpeg($this->sur_file);        } elseif ($this->type == 'gif') {            $this->tem_file = imagecreatefromgif($this->sur_file);        } elseif ($this->type == 'png') {            $this->tem_file = imagecreatefrompng($this->sur_file);        } elseif ($this->type == 'bmp') {            $this->tem_file = imagecreatefrombmp($this->sur_file); //bmp.php中包含        }    }    //圖片生成函數(shù)    private function new_img() {        $ratio = ($this->width) / ($this->height); //原圖比例        $resize_ratio = ($this->resize_width) / ($this->resize_height); //縮略后比例        $newimg = imagecreatetruecolor($this->resize_width, $this->resize_height); //生成新圖片        imagealphablending($newimg, false); //這里很重要,意思是不合并顏色,直接用$img圖像顏色替換,包括透明色;        imagesavealpha($newimg, true);        if ($this->tag == 0) { //按固定高寬截取縮略圖            $newimg = imagecreatetruecolor($this->resize_width, $this->resize_height); //生成新圖片            if ($ratio >= $resize_ratio) {//即等比例下,縮略圖的高比原圖長,因此高不變                imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, $this->resize_width, $this->resize_height, (($this->height) * $resize_ratio), $this->height);            } elseif ($ratio tem_file, 0, 0, 0, 0, $this->resize_width, $this->resize_height, $this->width, (($this->width) / $resize_ratio));            }        } elseif ($this->tag == 1) { //按固定比例或最大長度縮小            if ($this->sca_max width) * ($this->sca_max)), (($this->height) * ($this->sca_max))); //生成新圖片                imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, (($this->width) * ($this->sca_max)), (($this->height) * ($this->sca_max)), $this->width, $this->height);            } elseif ($this->sca_max > 1) { //按某個最大長度縮小                if ($ratio >= 1) { //寬比高長                    $newimg = imagecreatetruecolor($this->sca_max, ($this->sca_max / $ratio)); //生成新圖片                    imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, $this->sca_max, ($this->sca_max / $ratio), $this->width, $this->height);                } else {                    $newimg = imagecreatetruecolor(($this->sca_max * $ratio), $this->sca_max); //生成新圖片                    imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, ($this->sca_max * $ratio), $this->sca_max, $this->width, $this->height);                }            }        } elseif ($this->tag == -1) { //按某個寬度或某個高度縮小            if ($resize_ratio >= 1) {//新高小于新寬,則圖片按新寬度縮小                $newimg = imagecreatetruecolor($this->resize_width, ($this->resize_width / $ratio)); //生成新圖片                imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, $this->resize_width, ($this->resize_width / $ratio), $this->width, $this->height);            } elseif ($resize_ratio resize_height * $ratio), $this->resize_height); //生成新圖片                imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, ($this->resize_height * $ratio), $this->resize_height, $this->width, $this->height);            }        }        //輸出新圖片        if ($this->type == 'jpeg' || $this->type == 'jpg') {            imagejpeg($newimg, $this->des_file);        } elseif ($this->type == 'gif') {            imagegif($newimg, $this->des_file);        } elseif ($this->type == 'png') {            imagepng($newimg, $this->des_file);        } elseif ($this->type == 'bmp') {            imagebmp($newimg, $this->des_file); //bmp.php中包含        }    }#function new_img() end}