Example of PHP scale image generation thumbnail function

/*
*@im //Picture resources that need to be scaled
*@filetype //The thumbnail file type produced
*@dstimW //The width of the scaled picture
*@dstimH //Height of the zoomed picture
*@thumbname //Thumbnail file name
// WWW.JBXUE.COM
function makethumb($im,$dstimW,$dstimH,$thumbname,$filetype){
//Get im The width and height of
$pic_W=imagesx($im);
$pic_H=imagesy($im);
$arr = array();
swith($filetype){
case 'jpg':
$arr[$ filetype]="imagejpeg";
break;
case 'png';
$arr[$filetype]="imagepng";
break;
case 'jif';
$arr[$filetype]="imagegif";
 }
if(($dstimgW && $dstimgW<$pic_W) || ($dstimgH && $dstimgH<$pic_H) ){
if($dstimgW && $dstimgW<$pic_W){
$dsimgWratio = $dstimgW / $pic_w ;
$resizereagW =true;
}
if($dstimgH && $ $dstimgH <$pic_H){
$dsimgHratio = $dstimgH/$pic_H;
$resizerreagH =true;
}
//Thumbnail width and height For the original image aspect ratio, take the smallest one
if($resizereagW && $resizerreagH){
if($dsimgWratio<$dsimgHratio)
$radio = $dsimgWratio;
else
$radio = $dsimgHratio;
}
if( $resizereagW && !$resizerreagH ){
$radio = $dsimgWratio;
}
if(!$resizereagW && $resizerreagH){
 $radio = $dsimgHratio ;
}
$imgnewW = $pic_W * $radio;
$imgnewH = $pic_H * $radio;
if(function_exists("imgcopyresampled")){
 //Create the target resource canvas
$dst = imagecreatetruecolor ($imgnewW, $imgnewH);
imagecopyresampled ($dst,$im,0,0 ,0,0,$imgnewW,$imgnewH,$pic_W,$pic_H);
}else{
 $dst=imagecreate($imgnewW, $imgnewH);
 imagecopyresized ($dst, $im,0,0,0, 0,$imgnewW,$imgnewH,$imgnewH,$pic_W,$pic_H);
}
$arr[$filetype]($dst,$thumbname.".$filetype");
imagedestroy ($dst);
} else{//The width and height of the thumbnail itself are already greater than the width and height of the original image
 //Then the width and height of the thumbnail are the width and height of the original image
 $arr[$filetype] ($im,$thumbname.".$filetype");
 imagedestroy();
}
}
?>