function ResizeImg2($strSourceImagePath, $strDestImagePath, $intMaxWidth = 200, $intMaxHeight = 200)
{
    $arrImageProps = getimagesize($strSourceImagePath);
    $intImgWidth   = $arrImageProps[0];
    $intImgHeight  = $arrImageProps[1];
    $intImgType    = $arrImageProps[2];
 
    switch( $intImgType) {
        case 1: $rscImg = ImageCreateFromGif($strSourceImagePath);  break;
        case 2: $rscImg = ImageCreateFromJpeg($strSourceImagePath); break;
        case 3: $rscImg = ImageCreateFromPng($strSourceImagePath);  break;
        default: return false;
    }
 
    if ( !$rscImg) return false;
 
    if ($intImgWidth > $intImgHeight) {
        $fltRatio = floatval($intMaxWidth / $intImgWidth);
    } else {
        $fltRatio = floatval($intMaxHeight / $intImgHeight);
    }
 
    $intNewWidth  = intval($fltRatio * $intImgWidth);
    $intNewHeight = intval($fltRatio * $intImgHeight);
 
    $rscNewImg = ImageCreate($intNewWidth, $intNewHeight);
    if (!ImageCopyResized($rscNewImg, $rscImg, 0, 0,0, 0, $intNewWidth, $intNewHeight, $intImgWidth, $intImgHeight)) return false;
 
    switch($intImgType) {
        case 1:  $retVal = ImageGIF($rscNewImg, $strDestImagePath);  break;
        case 3:  $retVal = ImagePNG($rscNewImg, $strDestImagePath);  break;
        case 2:  $retVal = ImageJPEG($rscNewImg, $strDestImagePath, 90); break;
        default: return false;
    }
 
    ImageDestroy($rscNewImg);
 
    return true;
}
 
// Тест:
$strTestImgPath = dirname(__FILE__).'/testimg.gif';
$strDestImgPath = dirname(__FILE__).'/testimg.preview.gif';
 
print (int)ResizeImg2($strTestImgPath, $strDestImgPath, 300, 300);

function resize($cur_dir, $cur_file, $newwidth, $output_dir) {
    $dir_name = $cur_dir;
    $olddir = getcwd();
    $dir = opendir($dir_name);
    $filename = $cur_file;
    $format='';
    if(preg_match("/.jpg/i", "$filename"))
    {
        $format = 'image/jpeg';
    }
    if (preg_match("/.gif/i", "$filename"))
    {
        $format = 'image/gif';
    }
    if(preg_match("/.png/i", "$filename"))
    {
        $format = 'image/png';
    }
    if($format!='')
    {
        list($width, $height) = getimagesize($filename);
        $newheight=$height*$newwidth/$width;
        switch($format)
        {
            case 'image/jpeg':
            $source = imagecreatefromjpeg($filename);
            break;
            case 'image/gif';
            $source = imagecreatefromgif($filename);
            break;
            case 'image/png':
            $source = imagecreatefrompng($filename);
            break;
        }
        $thumb = imagecreatetruecolor($newwidth,$newheight);
        imagealphablending($thumb, false);
        $source = @imagecreatefromjpeg("$filename");
        imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
        $filename="$output_dir/$filename";
        @imagejpeg($thumb, $filename);
    }
}
 
//call this function using 
resize("./input folder", "picture_file_name", "width", "./output folder");
 

/**
* Resize an image and keep the proportions
* @author Allison Beckwith <allison@planetargon.com>
* @param string $filename
* @param integer $max_width
* @param integer $max_height
* @return image
*/
function resizeImage($filename, $max_width, $max_height)
{
   list($orig_width, $orig_height) = getimagesize($filename);
   $width = $orig_width;
   $height = $orig_height;
   # taller
   if ($height > $max_height) {
       $width = ($max_height / $height) * $width;
       $height = $max_height;
   }
   # wider
   if ($width > $max_width) {
       $height = ($max_width / $width) * $height;
       $width = $max_width;
   }
   $image_p = imagecreatetruecolor($width, $height);
   $image = imagecreatefromjpeg($filename);
   imagecopyresampled($image_p, $image, 0, 0, 0, 0, 
                                    $width, $height, $orig_width, $orig_height);
   return $image_p;
}
 

header('Content-type: image/jpeg');
//$myimage = resizeImage('filename', 'newwidthmax', 'newheightmax');
$myimage = resizeImage('test.jpg', '150', '120');
print $myimage;
function resizeImage($filename, $newwidth, $newheight){
    list($width, $height) = getimagesize($filename);
    if($width > $height && $newheight < $height){
        $newheight = $height / ($width / $newwidth);
    } else if ($width < $height && $newwidth < $width) {
        $newwidth = $width / ($height / $newheight);
    } else {
        $newwidth = $width;
        $newheight = $height;
    }
    $thumb = imagecreatetruecolor($newwidth, $newheight);
    $source = imagecreatefromjpeg($filename);
    imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
    return imagejpeg($thumb);
}

$picture = ""; # picture fileNAME here. not address
$max=150;    # maximum size of 1 side of the picture.
/*
here you can insert any specific "if-else",
or "switch" type of detector of what type of picture this is.
in this example i'll use standard JPG
*/
$src_img=ImagecreateFromJpeg($picture);
$oh = imagesy($src_img);  # original height
$ow = imagesx($src_img);  # original width
$new_h = $oh;
$new_w = $ow;
if($oh > $max || $ow > $max){
    $r = $oh/$ow;
    $new_h = ($oh > $ow) ? $max : $max*$r;
    $new_w = $new_h/$r;
}
// note TrueColor does 256 and not.. 8
$dst_img = ImageCreateTrueColor($new_w,$new_h);
ImageCopyResized($dst_img, $src_img, 0,0,0,0, $new_w, $new_h, ImageSX($src_img), ImageSY($src_img));
ImageJpeg($dst_img, "th_$picture");

function img_resize($src, $dest, $width, $height, $rgb = 0x000000, $quality = 100) {  
    if (!file_exists($src)) {  
        return false;  
    }  
 
    $size = getimagesize($src);  
 
    if ($size === false) {  
        return false;  
    }  
 
    $format = strtolower(substr($size['mime'], strpos($size['mime'], '/') + 1));  
    $icfunc = 'imagecreatefrom'.$format;  
 
    if (!function_exists($icfunc)) {  
        return false;  
    }  
 
    $x_ratio = $width  / $size[0];  
    $y_ratio = $height / $size[1];  
 
    if ($height == 0) {  
 
        $y_ratio = $x_ratio;  
        $height  = $y_ratio * $size[1];  
 
    } elseif ($width == 0) {  
 
        $x_ratio = $y_ratio;  
        $width   = $x_ratio * $size[0];  
 
    }  
 
    $ratio       = min($x_ratio, $y_ratio);  
    $use_x_ratio = ($x_ratio == $ratio);  
 
    $new_width   = $use_x_ratio  ? $width  : floor($size[0] * $ratio);  
    $new_height  = !$use_x_ratio ? $height : floor($size[1] * $ratio);  
    $new_left    = $use_x_ratio  ? 0 : floor(($width - $new_width)   / 2);  
    $new_top     = !$use_x_ratio ? 0 : floor(($height - $new_height) / 2);  
 
    $isrc  = $icfunc($src);  
    $idest = imagecreatetruecolor($width, $height);  
    $rgb2 = imagecolorallocate($idest, 245, 245, 245);
    imagefill($idest, 0, 0, $rgb2);  
    imagecopyresampled($idest, $isrc, $new_left, $new_top, 0, 0, $new_width, $new_height, $size[0], $size[1]);  
 
    imagejpeg($idest, $dest, $quality);  
 
    imagedestroy($isrc);  
    imagedestroy($idest);  
 
    return true;  
}