Imagecopyresampled

imagecopyresampled($image_p, $image, 0, 0, 0, 0, $NewWidth, $NewHeight, $OrigWidth, $OrigHeight);

  function Resizer(  $filename, //cesta k souboru, ktery chcete zmensit   
                     $copypath, //cesta, kam zmenseny soubor ulozit  
                     $MaxWidth, //maximalni sirka zmenseneho obrazku  
                     $MaxHeight, //maximalni vyska zmenseneho obrazku 
                     $pripona)   //pripona
    { 

    //zjistime puvodni velikost obrazku  
    list($OrigWidth, $OrigHeight) = getimagesize($filename); 
    
    //hodnota 0 v parametrech MaxWidth resp. MaxHeight znamena, 
    //ze sirka resp. vyska vysledku muze byt libovolna  
    if ($MaxWidth == 0) $MaxWidth = $OrigWidth; 
    if ($MaxHeight == 0) $MaxHeight = $OrigHeight; 
    
    //nyni vypocitam pomer zmenseni  
    $pw = $OrigWidth / $MaxWidth; 
    $ph = $OrigHeight / $MaxHeight; 
    
    if ($pw > $ph) $p = $pw; 
    else  $p = $ph; 
    
    if ($p < 1) $p = 1; 
    
    //v p ted mame pomer pro zmenseni 
    //vypocitame vysku a sirku zmenseneho obrazku  
    $NewWidth = (int)$OrigWidth / $p; 
    $NewHeight = (int)$OrigHeight / $p; 
    
    //vytvorime novy obrazek pozadovane vysky a sirky  
    $image_p = imagecreatetruecolor($NewWidth, $NewHeight); 
    echo $pripona;
    //otevreme puvodni obrazek se souboru  
    switch($pripona) 
    {
      case 'png': $image = imagecreatepng($filename); echo "png"; break;
      case 'gif': $image = imagecreategif($filename); echo "gif"; break;
      case 'jpg': $image = imagecreate($filename); echo "jpg"; break;
    }

 

    //a okopirujeme zmenseny puvodni obrazek do noveho  
    imagecopyresampled($image_p, $image, 0, 0, 0, 0, $NewWidth, $NewHeight, $OrigWidth, $OrigHeight); 

    //a ulozime  
 
    switch($pripona) 
    {
      case 'png': imagepng($image_p, $copypath, 100); echo "png"; break;
      case 'gif': imagegif($image_p, $copypath, 100); echo "gif"; break;
      case 'jpg': imagejpeg($image_p, $copypath, 100);; echo "jpg"; break;
    }
  }