php 压缩图片处理png、gif背景变黑问题

直接展示代码

   /**
     * 压缩图片
     * @param $imgsrc 图片路径
     * @param string $imgdst   压缩后保存路径
     * @param int $quality   压缩图片的质量
     * @return string
     */
    public function compressedImage($imgsrc, $imgdst="",$quality=75) {
         //绝对路径  或者相对路径去掉前面的/
        //if (!is_file($imgsrc))$imgsrc= __DIR__ . '/'.$imgsrc;
        list($width, $height, $type) = getimagesize($imgsrc);
        if ($imgdst==""){

            $position1 = strrpos($imgsrc,'/');
            $path1 = substr($imgsrc,0,$position1);
            $name1=substr($imgsrc,$position1+1);
            $imgdst=$path1."/thumb/".$name1;

//            $arrtmp=explode("/",$imgsrc);
//            array_splice($arrtmp, count($arrtmp)-1, 0, array("thumb"));
//            $imgdst=implode("/",$arrtmp);
        }

        if (is_file($imgdst)){return $imgdst;}

        $new_width = $width;//压缩后的图片宽
        $new_height = $height;//压缩后的图片高

        if($width >= 620){
            $per = 620 / $width;//计算比例
            $new_width = $width * $per;
            $new_height = $height * $per;
        }
        //print_r($type);exit();
        //创建文件交
        $position = strrpos($imgdst,'/');
        $path = substr($imgdst,0,$position);
        if(!file_exists($path)){mkdir($path,0777,true);}
        switch ($type) {
            case 1:
                $giftype = check_gifcartoon($imgsrc);
                if ($giftype) {
                    //header('Content-Type:image/gif');
                    $image_wp = imagecreatetruecolor($new_width, $new_height);

                    /* --- 用以处理缩放gif和png图透明背景变黑色问题 开始 --- */
                    $color = imagecolorallocate($image_wp,255,255,255);
                    imagecolortransparent($image_wp,$color);
                    imagefill($image_wp,0,0,$color);
                    /* --- 用以处理缩放gif和png图透明背景变黑色问题 结束 --- */

                    $image = imagecreatefromgif($imgsrc);
                    imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
                    //90代表的是质量、压缩图片容量大小
                    imagejpeg($image_wp, $imgdst, $quality);
                    imagedestroy($image_wp);
                    imagedestroy($image);
                }
                break;
            case 2:
                //header('Content-Type:image/jpeg');
                $image_wp = imagecreatetruecolor($new_width, $new_height);
                $image = imagecreatefromjpeg($imgsrc);
                imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
                //90代表的是质量、压缩图片容量大小
                imagejpeg($image_wp, $imgdst, $quality);
                imagedestroy($image_wp);
                imagedestroy($image);
                break;
            case 3:
                //header('Content-Type:image/png');
                $image_wp = imagecreatetruecolor($new_width, $new_height);

                /* --- 用以处理缩放gif和png图透明背景变黑色问题 开始 --- */
                $color = imagecolorallocate($image_wp,255,255,255);
                imagecolortransparent($image_wp,$color);
                imagefill($image_wp,0,0,$color);
                /* --- 用以处理缩放gif和png图透明背景变黑色问题 结束 --- */

                $image = imagecreatefrompng($imgsrc);
                imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
                //90代表的是质量、压缩图片容量大小
                imagejpeg($image_wp, $imgdst, $quality);
                imagedestroy($image_wp);
                imagedestroy($image);
                break;
        }
        return $imgdst;
    }