PHP code to generate thumbnail images based on requests and save them to the Linux image server

/**
 * Thumbnail Image Linux Image Server
 * edit bbs.it-home.org
*/
 $picID=$_GET['imgID'];
 $picTypes=".".$_GET['imgType'];
 $picWidth= $_GET['ImgWidth'];
 if($picID!="")
 {
 //The request is for a small picture
 if($picWidth>0){
 //If the small picture exists
 if(file_exists($ picID."_".$picWidth.$picTypes))
 {
 outputImg($picID."_".$picWidth.$picTypes);
 }else
 {
 if(file_exists($picID."_0".$ picTypes)){
 //If the thumbnail does not exist, generate the thumbnail directly
 resizeImg($picID."_0".$picTypes,$picWidth,$picWidth,$picID."_".$picWidth.$picTypes);
 //Output
 outputImg($picID."_".$picWidth.$picTypes);
 }else
 {
 //If the large image does not exist
 resizeImg('noDefaultImage.gif',$picWidth,$picWidth,noDefaultImage. "_".$picWidth.".gif");
 //Output
 outputImg($picID."_".$picWidth.$picTypes);
 }
 }
 }
 //Determine whether a large image exists in the file
 if(file_exists($picID."_0".$picTypes))
 {
 $img_file = $picID."_0".$picTypes;
 outputImg($img_file);
 }
 else
 {
 //if it does not exist Image
 $img_file = 'noDefaultImage.gif';
 outputImg($img_file);
 }
 }
 //Output image
 function outputImg($img_file)
 {
 $fp = fopen($img_file, 'rb');
 $content = fread($fp, filesize($img_file)); //Binary data
 fclose($fp);
 header('Content-Type: image/gif');
 echo $content;
 }
 / **
 * Generate thumbnails
 * $srcName---- is the original image path
 * $newWidth, $newHeight---- are the maximum width and height of the thumbnail respectively
 * $newName---- is the thumbnail file name ( including path)
 * @param string $srcName
 * @param int $newWidth
 * @param int $newHeight
 * @param string $newName
 * return viod
*/
 function resizeImg($srcName,$newWidth,$newHeight,$newName="")
 {
 if($newName=="")
 {
 $nameArr=explode('.', $srcName);
 $expName=array_pop($nameArr);
 $expName=$expName;
 array_push($nameArr,$expName);
 $newName = implode('.',$nameArr);
 }
 $info = "";
 $data = getimagesize($srcName,$info);
 switch ($data[2])
 {
 case 1:
 if(!function_exists("imagecreatefromgif")){
 echo "Your GD The library cannot use images in GIF format, please use Jpeg or PNG format! return ";
 exit();
 }
 $im = ImageCreateFromGIF($srcName);
 break;
 case 2:
 if(!function_exists("imagecreatefromjpeg")){
 echo "Your GD library cannot use jpeg format For pictures, please use pictures in other formats!返回";
                                    exit();
                            }
                            $im = ImageCreateFromJpeg($srcName);
                            break;
                    case 3:
                            $im = ImageCreateFromPNG($srcName);
                            break;
            }
            $srcW=ImageSX($im);
            $srcH=ImageSY($im);
            $newWidthH=$newWidth/$newHeight;
            $srcWH=$srcW/$srcH;
            if($newWidthH<=$srcWH){
                    $ftoW=$newWidth;
                    $ftoH=$ftoW*($srcH/$srcW);
            }
            else{
                    $ftoH=$newHeight;
                    $ftoW=$ftoH*($srcW/$srcH);
            }
            if($srcW>$newWidth||$srcH>$newHeight)
            {
                    if(function_exists("imagecreatetruecolor"))
                    {
                            @$ni = ImageCreateTrueColor($ftoW,$ftoH);
                            if($ni) ImageCopyResampled($ni,$im,0,0,0,0,$ftoW,$ftoH,$srcW,$srcH);
                            else
                            {
                                    $ni=ImageCreate($ftoW,$ftoH);
                                    ImageCopyResized($ni,$im,0,0,0,0,$ftoW,$ftoH,$srcW,$srcH);
                            }
                    }
                    else
                    {
                            $ni=ImageCreate($ftoW,$ftoH);
                            ImageCopyResized($ni,$im,0,0,0,0,$ftoW,$ftoH,$srcW,$srcH);
                    }
                    if(function_exists('imagejpeg')) ImageJpeg($ni,$newName);
                    else ImagePNG($ni,$newName);
                    ImageDestroy($ni);
            }
            ImageDestroy($im);
    }
?>