ользую модифицированную версию класса SimpleImage.php:http://www.white-hat-web-design.co.uk/articles/php-image-resizing.php

Правки, которые я нашел на phpfreaks (http://www.phpfreaks.com/forums/index.php?topic=301811.0), но когда я использую, png изменяется, но прозрачность становится черной.

Я звоню как:

 $max_width = 200; // set a max width
 $max_height = 150; // set a max height
 if($imgW > $imgH){ // width is greater
      // resize to width up to max
      if($imgW > $max_width) $image->resizeToWidth($max_width);
 }
 else { // height is greater
      // resize to height up to max
      if($imgH > $max_height) $image->resizeToHeight($max_height);
 }

 $image->save($_SERVER['DOCUMENT_ROOT']."/path/" . $new_filename);

Я не уверен, чего не хватает. Любая помощь приветствуется ...

class SimpleImage {
     var $image;
     var $image_type;

     function load($filename) {
        $image_info = getimagesize($filename);
        $this->image_type = $image_info[2];
        if( $this->image_type == IMAGETYPE_JPEG ) {
            $this->image = imagecreatefromjpeg($filename);
        } elseif( $this->image_type == IMAGETYPE_GIF ) {
            $this->image = imagecreatefromgif($filename);
        } elseif( $this->image_type == IMAGETYPE_PNG ) {
            $this->image = imagecreatefrompng($filename);
        }
    }
    function save($filename, $image_type=IMAGETYPE_JPEG, $compression=75, $permissions=null) {
        if( $image_type == IMAGETYPE_JPEG ) {
            imagejpeg($this->image,$filename,$compression);
        } elseif( $image_type == IMAGETYPE_GIF ) {
            imagegif($this->image,$filename);
        } elseif( $image_type == IMAGETYPE_PNG ) {
            imagepng($this->image,$filename);
        }
        if( $permissions != null) {
            chmod($filename,$permissions);
        }
    }

    function output($image_type=IMAGETYPE_JPEG) {
        if( $image_type == IMAGETYPE_JPEG ) {
            imagejpeg($this->image);
        } elseif( $image_type == IMAGETYPE_GIF ) {
            imagegif($this->image);
        } elseif( $image_type == IMAGETYPE_PNG ) {
            imageAlphaBlending($this->image, true);
            imageSaveAlpha($this->image, true);
            imagepng($this->image);
        }   
    }

    function getWidth() {
        return imagesx($this->image);
    }
    function getHeight() {
        return imagesy($this->image);
    }
    function resizeToHeight($height) {
        $ratio = $height / $this->getHeight();
        $width = $this->getWidth() * $ratio;
        $this->resize($width,$height);
    }
    function resizeToWidth($width) {
        $ratio = $width / $this->getWidth();
        $height = $this->getheight() * $ratio;
        $this->resize($width,$height);
    }
    function scale($scale) {
        $width = $this->getWidth() * $scale/100;
        $height = $this->getheight() * $scale/100;
        $this->resize($width,$height);
    }
    function resize($width,$height) {

        // ADDED CODE IS HERE - NOT SURE WHY IT DOESN'T WORK FOR PNG

        // Setup new image
        $new_image = imagecreatetruecolor($width, $height);
        // These parameters are required for handling PNG files.
        imagealphablending($new_image, false);
        imagesavealpha($new_image,true);
        $transparent = imagecolorallocatealpha($new_image, 255, 255, 255, 127);
        imagefilledrectangle($new_image, 0, 0, $width, $height, $transparent);
        // Resize image
        imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
        $this->image = $new_image;
    }
}