Grafika\Gd\Helper\GifHelper::resize PHP Method

    public function resize($blocks, $newW, $newH)
    {
        $images = $this->splitFrames($blocks);
        // Loop on individual images and resize them using Gd
        $firstFrameGd = null;
        foreach ($images as $imageIndex => $image) {
            $hex = $this->encode($image);
            $binaryRaw = pack('H*', $hex);
            // Utilize gd for resizing
            $old = imagecreatefromstring($binaryRaw);
            $width = imagesx($old);
            $height = imagesy($old);
            $new = imagecreatetruecolor($newW, $newH);
            // Create a blank image
            if ($firstFrameGd) {
                $new = $firstFrameGd;
            }
            // Account for frame imageLeft and imageTop
            $cX = $newW / $blocks['canvasWidth'];
            // change x
            $dX = $image['frames'][0]['imageLeft'];
            $cY = $newH / $blocks['canvasHeight'];
            $dY = $image['frames'][0]['imageTop'];
            imagecopyresampled($new, $old, $dX * $cX, $dY * $cY, 0, 0, $image['frames'][0]['imageWidth'] * $cX, $image['frames'][0]['imageHeight'] * $cY, $width, $height);
            ob_start();
            imagegif($new);
            $binaryRaw = ob_get_contents();
            ob_end_clean();
            if ($firstFrameGd === null) {
                $firstFrameGd = $new;
            }
            // Hex of resized
            $bytes = $this->load($binaryRaw);
            $hexNew = $this->decode($bytes);
            // Update original frames with hex from resized frames
            $blocks['frames'][$imageIndex]['imageWidth'] = $hexNew['frames'][0]['imageWidth'];
            $blocks['frames'][$imageIndex]['imageHeight'] = $hexNew['frames'][0]['imageHeight'];
            $blocks['frames'][$imageIndex]['imageLeft'] = $hexNew['frames'][0]['imageLeft'];
            $blocks['frames'][$imageIndex]['imageTop'] = $hexNew['frames'][0]['imageTop'];
            $blocks['frames'][$imageIndex]['imageData'] = $hexNew['frames'][0]['imageData'];
            // We use local color tables on each frame. This will result in faster processing since we dont have to process the global color table at the cost of a larger file size.
            $blocks['frames'][$imageIndex]['localColorTableFlag'] = $hexNew['globalColorTableFlag'];
            $blocks['frames'][$imageIndex]['localColorTable'] = $hexNew['globalColorTable'];
            $blocks['frames'][$imageIndex]['sizeOfLocalColorTable'] = $hexNew['sizeOfGlobalColorTable'];
            $blocks['frames'][$imageIndex]['transparentColorFlag'] = 0;
        }
        // Update dimensions or else imagecreatefromgif will choke.
        $blocks['canvasWidth'] = $newW;
        $blocks['canvasHeight'] = $newH;
        // Disable flickering bug. Also we are using localColorTable anyways.
        $blocks['globalColorTableFlag'] = 0;
        $blocks['globalColorTable'] = '';
        return $blocks;
    }

 /**
  * Resize helper function.
  *
  * @param Image $image
  * @param int $newWidth
  * @param int $newHeight
  * @param int $targetX
  * @param int $targetY
  * @param int $srcX
  * @param int $srcY
  *
  */
 private function _resize(&$image, $newWidth, $newHeight, $targetX = 0, $targetY = 0, $srcX = 0, $srcY = 0)
 {
     //        $this->_imageCheck();
     if ($image->isAnimated()) {
         // Animated GIF
         $gift = new GifHelper();
         $blocks = $gift->resize($image->getBlocks(), $newWidth, $newHeight);
         // Resize image instance
         $image = new Image($image->getCore(), $image->getImageFile(), $newWidth, $newHeight, $image->getType(), $blocks, true);
     } else {
         // Create blank image
         $newImage = Image::createBlank($newWidth, $newHeight);
         if (ImageType::PNG === $image->getType()) {
             // Preserve PNG transparency
             $newImage->fullAlphaMode(true);
         }
         imagecopyresampled($newImage->getCore(), $image->getCore(), $targetX, $targetY, $srcX, $srcY, $newWidth, $newHeight, $image->getWidth(), $image->getHeight());
         // Free memory of old resource
         imagedestroy($image->getCore());
         // Resize image instance
         $image = new Image($newImage->getCore(), $image->getImageFile(), $newWidth, $newHeight, $image->getType());
     }
 }