PHP uses GD library to generate thumbnails

 < input type="submit" value="Upload 1" />




  header("content-type:text/html;charset=gbk");
 ini_set( "date.timezone","Asia/chong");
 //Judge whether the file is empty
 if(empty($_FILES)){
 echo "The uploaded file is too large";
 exit;
 }
 //Judge the file Check if there are any errors in the upload
 if($_FILES['pic']['error']){
 echo "Upload file";
 exit;
 }
 //Determine whether the file type is illegal to obtain the file suffix
 $allowtype=array( "jpg","png","jpeg","gif");
 $a=explode('.',$_FILES['pic']['name']);
 $index=count($a) -1;
 $ex=strtolower($a[$index]);
 if(!in_array($ex,$allowtype)){
 echo "Illegal file upload";
 exit;
 }
 $file=date( 'YmdHis').rand().".".$ex;
 $src=$_FILES['pic']['tmp_name'];
 $des="upload/".$file;
 $rs=move_uploaded_file ($src,$des);


 //Thumbnail
 //Read uploaded images
 $image=imagecreatefromjpeg($des);
 $a=getimagesize($des);
 $w=$a[ 0];
 $h=$a[1];
 if($w>$h){
 $width=300;
 $height=$width/$w*$h;
 }else if($w< $h){
 $height=300;
 $width=$height/$h*$w;
 }else{
 $width=300;
 $height=300;
 }
 //Create a new blank image
 $ newimage=imagecreatetruecolor($width, $height);
 //Copy the source image content and copy the new image
 imagecopyresized($newimage, $image, 0,0, 0,0, $width, $height, $w, $h) ;
 $filename="upload/s_".$file;
 imagejpeg($newimage,$filename);

php