php 压缩各格式图片,处理png格式图片背景黑色问题

    //压缩图片

//$srcFile 文件名

//$percent压缩比

//$quality图片质量

    function pictumb($srcFile,$percent,$quality){

        $dstFile = $srcFile;//保留名字

        //header('Content-Type: image/jpeg');

        // 获取新的尺寸

        list($width, $height) = getimagesize($srcFile);

        if ($width>600){

            $new_width = $width / $percent;

            $new_height = $height / $percent;

        }else{

            $new_width =$width;

            $new_height = $height;

        }

            // 重新取样

            $image_p = imagecreatetruecolor($new_width, $new_height);

            //设置颜色

            $color=imagecolorallocate($image_p,255,255,255); 

            imagecolortransparent($image_p,$color); 

            imagefill($image_p,0,0,$color); 

            //获取格式

            $format=substr($srcFile,strrpos($srcFile, '.'));

            switch ($format) {

                case '.png':

                    $image=imagecreatefrompng($srcFile);

                    break;

                case '.jpeg':

                    $image=imagecreatefromjpeg($srcFile);

                    break;

                case '.bmp':

                    $image=imagecreatefromwbmp($srcFile);

                    break;

                case '.gif':

                    $image=imagecreatefromgif($srcFile);

                    break;

                default:

                     $image=imagecreatefromjpeg($srcFile);

                    break;

            }

            imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);

            chmod($srcFile,0777);//unlink函数要求对删除的图片有777的权限

            unlink($srcFile);//先删除图片，在进行保存

            // 输出

            switch ($format) {

                case '.png':

                    imagepng($image_p,$dstFile);

                    break;

                case '.jpeg':

                    imagejpeg($image_p,$dstFile, $quality);

                    break;

                case '.bmp':

                    imagewbmp($image_p,$dstFile);

                    break;

                case '.gif':

                    imagegif( $image_p,$dstFile);

                    break;

                default:

                     imagejpeg($image_p,$dstFile,$quality);

                    break;

            }

    }