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<?php
/**
 * @version                              $Id: ImageType_GD.php 10831 2013-05-29 19:32:17Z btowles $
 * @author                               RocketTheme http://www.rockettheme.com
 * @copyright                            Copyright (C) 2007 - 2016 RocketTheme, LLC
 * @license                              http://www.gnu.org/licenses/gpl-2.0.html GNU/GPLv2 only
 *
 * Derived from
 *
 * PhpThumb GD Thumb Class Definition File
 *
 * This file contains the definition for the RokCommon_Image_ImageType_GD object
 *
 * PHP Version 5 with GD 2.0+
 * PhpThumb : PHP Thumb Library <http://phpthumb.gxdlabs.com>
 * Copyright (c) 2009, Ian Selby/Gen X Design
 *
 * Author(s): Ian Selby <ian@gen-x-design.com>
 *
 * Licensed under the MIT License
 * Redistributions of files must retain the above copyright notice.
 *
 * @author                               Ian Selby <ian@gen-x-design.com>
 * @copyright                            Copyright (c) 2009 Gen X Design
 * @link                                 http://phpthumb.gxdlabs.com
 * @license                              http://www.opensource.org/licenses/mit-license.php The MIT License
 * @version                              3.0
 * @package                              PhpThumb
 * @filesource
 */

/**
 * RokCommon_Image_ImageType_GD Class Definition
 *
 * This is the GD Implementation of the PHP Thumb library.
 *
 * @package    PhpThumb
 * @subpackage Core
 */
class RokCommon_Image_ImageType_GD extends RokCommon_Image_AbstractImageType
{
	/**
	 * The prior image (before manipulation)
	 *
	 * @var resource
	 */
	protected $oldImage;
	/**
	 * The working image (used during manipulation)
	 *
	 * @var resource
	 */
	protected $workingImage;
	/**
	 * The current dimensions of the image
	 *
	 * @var array
	 */
	protected $currentDimensions;
	/**
	 * The new, calculated dimensions of the image
	 *
	 * @var array
	 */
	protected $newDimensions;

	/**
	 * The maximum width an image can be after resizing (in pixels)
	 *
	 * @var int
	 */
	protected $maxWidth;
	/**
	 * The maximum height an image can be after resizing (in pixels)
	 *
	 * @var int
	 */
	protected $maxHeight;
	/**
	 * The percentage to resize the image by
	 *
	 * @var int
	 */
	protected $percent;

	/**
	 * Class Constructor
	 *
	 * @return RokCommon_Image_ImageType_GD
	 *
	 * @param string $fileName
	 */
	public function __construct($fileName, array $options = array(), $isDataStream = false)
	{
		parent::__construct($fileName, $options, $isDataStream);

		$this->determineFormat();

		if ($this->isDataStream === false) {
			$this->verifyFormatCompatiblity();
		}

		switch ($this->format) {
			case 'GIF':
				$this->oldImage = imagecreatefromgif($this->fileName);
				break;
			case 'JPG':
				$this->oldImage = imagecreatefromjpeg($this->fileName);
				break;
			case 'PNG':
				$this->oldImage = imagecreatefrompng($this->fileName);
				break;
			case 'STRING':
				$this->oldImage = imagecreatefromstring($this->fileName);
				break;
		}

		$this->currentDimensions = array(
			'width'	 => imagesx($this->oldImage),
			'height'	=> imagesy($this->oldImage)
		);

		$this->setOptions($options);

		// TODO: Port gatherImageMeta to a separate function that can be called to extract exif data
	}

	/**
	 * Class Destructor
	 *
	 */
	public function __destruct()
	{
		if (is_resource($this->oldImage)) {
			imagedestroy($this->oldImage);
		}

		if (is_resource($this->workingImage)) {
			imagedestroy($this->workingImage);
		}
	}

	##############################
	# ----- API FUNCTIONS ------ #
	##############################

	/**
	 * Resizes an image to be no larger than $maxWidth or $maxHeight
	 *
	 * If either param is set to zero, then that dimension will not be considered as a part of the resize.
	 * Additionally, if $this->options['resizeUp'] is set to true (false by default), then this function will
	 * also scale the image up to the maximum dimensions provided.
	 *
	 * @param int $maxWidth  The maximum width of the image in pixels
	 * @param int $maxHeight The maximum height of the image in pixels
	 *
	 * @return RokCommon_Image_ImageType_GD
	 * @throws InvalidArgumentException
	 */
	public function resize($maxWidth = 0, $maxHeight = 0)
	{
		// make sure our arguments are valid
		if (!is_numeric($maxWidth)) {
			throw new InvalidArgumentException('$maxWidth must be numeric');
		}

		if (!is_numeric($maxHeight)) {
			throw new InvalidArgumentException('$maxHeight must be numeric');
		}

		// make sure we're not exceeding our image size if we're not supposed to
		if ($this->options['resizeUp'] === false) {
			$this->maxHeight = (intval($maxHeight) > $this->currentDimensions['height']) ? $this->currentDimensions['height'] : $maxHeight;
			$this->maxWidth  = (intval($maxWidth) > $this->currentDimensions['width']) ? $this->currentDimensions['width'] : $maxWidth;
		} else {
			$this->maxHeight = intval($maxHeight);
			$this->maxWidth  = intval($maxWidth);
		}

		// get the new dimensions...
		$this->calcImageSize($this->currentDimensions['width'], $this->currentDimensions['height']);

		// create the working image
		if (function_exists('imagecreatetruecolor')) {
			$this->workingImage = imagecreatetruecolor($this->newDimensions['newWidth'], $this->newDimensions['newHeight']);
		} else {
			$this->workingImage = imagecreate($this->newDimensions['newWidth'], $this->newDimensions['newHeight']);
		}

		$this->preserveAlpha();

		// and create the newly sized image
		imagecopyresampled($this->workingImage, $this->oldImage, 0, 0, 0, 0, $this->newDimensions['newWidth'], $this->newDimensions['newHeight'], $this->currentDimensions['width'], $this->currentDimensions['height']);

		// update all the variables and resources to be correct
		$this->oldImage                    = $this->workingImage;
		$this->currentDimensions['width']  = $this->newDimensions['newWidth'];
		$this->currentDimensions['height'] = $this->newDimensions['newHeight'];

		return $this;
	}

	/**
	 * Adaptively Resizes the Image
	 *
	 * This function attempts to get the image to as close to the provided dimensions as possible, and then crops the
	 * remaining overflow (from the center) to get the image to be the size specified
	 *
	 * @param int $maxWidth
	 * @param int $maxHeight
	 *
	 * @return RokCommon_Image_ImageType_GD
	 * @throws InvalidArgumentException
	 */
	public function adaptiveResize($width, $height)
	{
		// make sure our arguments are valid
		if (!is_numeric($width) || $width == 0) {
			throw new InvalidArgumentException('$width must be numeric and greater than zero');
		}

		if (!is_numeric($height) || $height == 0) {
			throw new InvalidArgumentException('$height must be numeric and greater than zero');
		}

		// make sure we're not exceeding our image size if we're not supposed to
		if ($this->options['resizeUp'] === false) {
			$this->maxHeight = (intval($height) > $this->currentDimensions['height']) ? $this->currentDimensions['height'] : $height;
			$this->maxWidth  = (intval($width) > $this->currentDimensions['width']) ? $this->currentDimensions['width'] : $width;
		} else {
			$this->maxHeight = intval($height);
			$this->maxWidth  = intval($width);
		}

		$this->calcImageSizeStrict($this->currentDimensions['width'], $this->currentDimensions['height']);

		// resize the image to be close to our desired dimensions
		$this->resize($this->newDimensions['newWidth'], $this->newDimensions['newHeight']);

		// reset the max dimensions...
		if ($this->options['resizeUp'] === false) {
			$this->maxHeight = (intval($height) > $this->currentDimensions['height']) ? $this->currentDimensions['height'] : $height;
			$this->maxWidth  = (intval($width) > $this->currentDimensions['width']) ? $this->currentDimensions['width'] : $width;
		} else {
			$this->maxHeight = intval($height);
			$this->maxWidth  = intval($width);
		}

		// create the working image
		if (function_exists('imagecreatetruecolor')) {
			$this->workingImage = imagecreatetruecolor($this->maxWidth, $this->maxHeight);
		} else {
			$this->workingImage = imagecreate($this->maxWidth, $this->maxHeight);
		}

		$this->preserveAlpha();

		$cropWidth  = $this->maxWidth;
		$cropHeight = $this->maxHeight;
		$cropX      = 0;
		$cropY      = 0;

		// now, figure out how to crop the rest of the image...
		if ($this->currentDimensions['width'] > $this->maxWidth) {
			$cropX = intval(($this->currentDimensions['width'] - $this->maxWidth) / 2);
		} elseif ($this->currentDimensions['height'] > $this->maxHeight) {
			$cropY = intval(($this->currentDimensions['height'] - $this->maxHeight) / 2);
		}

		imagecopyresampled($this->workingImage, $this->oldImage, 0, 0, $cropX, $cropY, $cropWidth, $cropHeight, $cropWidth, $cropHeight);

		// update all the variables and resources to be correct
		$this->oldImage                    = $this->workingImage;
		$this->currentDimensions['width']  = $this->maxWidth;
		$this->currentDimensions['height'] = $this->maxHeight;

		return $this;
	}

	/**
	 * Resizes an image by a given percent uniformly
	 *
	 * Percentage should be whole number representation (i.e. 1-100)
	 *
	 * @param int $percent
	 *
	 * @return RokCommon_Image_ImageType_GD
	 * @throws InvalidArgumentException
	 */
	public function resizePercent($percent = 0)
	{
		if (!is_numeric($percent)) {
			throw new InvalidArgumentException ('$percent must be numeric');
		}

		$this->percent = intval($percent);

		$this->calcImageSizePercent($this->currentDimensions['width'], $this->currentDimensions['height']);

		if (function_exists('imagecreatetruecolor')) {
			$this->workingImage = imagecreatetruecolor($this->newDimensions['newWidth'], $this->newDimensions['newHeight']);
		} else {
			$this->workingImage = imagecreate($this->newDimensions['newWidth'], $this->newDimensions['newHeight']);
		}

		$this->preserveAlpha();

		ImageCopyResampled($this->workingImage, $this->oldImage, 0, 0, 0, 0, $this->newDimensions['newWidth'], $this->newDimensions['newHeight'], $this->currentDimensions['width'], $this->currentDimensions['height']);

		$this->oldImage                    = $this->workingImage;
		$this->currentDimensions['width']  = $this->newDimensions['newWidth'];
		$this->currentDimensions['height'] = $this->newDimensions['newHeight'];

		return $this;
	}

	/**
	 * Crops an image from the center with provided dimensions
	 *
	 * If no height is given, the width will be used as a height, thus creating a square crop
	 *
	 * @param int $cropWidth
	 * @param int $cropHeight
	 *
	 * @return RokCommon_Image_ImageType_GD
	 * @throws InvalidArgumentException
	 */
	public function cropFromCenter($cropWidth, $cropHeight = null)
	{
		if (!is_numeric($cropWidth)) {
			throw new InvalidArgumentException('$cropWidth must be numeric');
		}

		if ($cropHeight !== null && !is_numeric($cropHeight)) {
			throw new InvalidArgumentException('$cropHeight must be numeric');
		}

		if ($cropHeight === null) {
			$cropHeight = $cropWidth;
		}

		$cropWidth  = ($this->currentDimensions['width'] < $cropWidth) ? $this->currentDimensions['width'] : $cropWidth;
		$cropHeight = ($this->currentDimensions['height'] < $cropHeight) ? $this->currentDimensions['height'] : $cropHeight;

		$cropX = intval(($this->currentDimensions['width'] - $cropWidth) / 2);
		$cropY = intval(($this->currentDimensions['height'] - $cropHeight) / 2);

		$this->crop($cropX, $cropY, $cropWidth, $cropHeight);

		return $this;
	}

	/**
	 * Vanilla Cropping - Crops from x,y with specified width and height
	 *
	 * @param int $startX
	 * @param int $startY
	 * @param int $cropWidth
	 * @param int $cropHeight
	 *
	 * @return RokCommon_Image_ImageType_GD
	 * @throws InvalidArgumentException
	 */
	public function crop($startX, $startY, $cropWidth, $cropHeight)
	{
		// validate input
		if (!is_numeric($startX)) {
			throw new InvalidArgumentException('$startX must be numeric');
		}

		if (!is_numeric($startY)) {
			throw new InvalidArgumentException('$startY must be numeric');
		}

		if (!is_numeric($cropWidth)) {
			throw new InvalidArgumentException('$cropWidth must be numeric');
		}

		if (!is_numeric($cropHeight)) {
			throw new InvalidArgumentException('$cropHeight must be numeric');
		}

		// do some calculations
		$cropWidth  = ($this->currentDimensions['width'] < $cropWidth) ? $this->currentDimensions['width'] : $cropWidth;
		$cropHeight = ($this->currentDimensions['height'] < $cropHeight) ? $this->currentDimensions['height'] : $cropHeight;

		// ensure everything's in bounds
		if (($startX + $cropWidth) > $this->currentDimensions['width']) {
			$startX = ($this->currentDimensions['width'] - $cropWidth);

		}

		if (($startY + $cropHeight) > $this->currentDimensions['height']) {
			$startY = ($this->currentDimensions['height'] - $cropHeight);
		}

		if ($startX < 0) {
			$startX = 0;
		}

		if ($startY < 0) {
			$startY = 0;
		}

		// create the working image
		if (function_exists('imagecreatetruecolor')) {
			$this->workingImage = imagecreatetruecolor($cropWidth, $cropHeight);
		} else {
			$this->workingImage = imagecreate($cropWidth, $cropHeight);
		}

		$this->preserveAlpha();

		imagecopyresampled($this->workingImage, $this->oldImage, 0, 0, $startX, $startY, $cropWidth, $cropHeight, $cropWidth, $cropHeight);

		$this->oldImage                    = $this->workingImage;
		$this->currentDimensions['width']  = $cropWidth;
		$this->currentDimensions['height'] = $cropHeight;

		return $this;
	}

	/**
	 * Rotates image either 90 degrees clockwise or counter-clockwise
	 *
	 * @param string $direction
	 *
	 * @retunrn RokCommon_Image_ImageType_GD
	 */
	public function rotateImage($direction = 'CW')
	{
		if ($direction == 'CW') {
			$this->rotateImageNDegrees(270);
		} else {
			$this->rotateImageNDegrees(90);
		}

		return $this;
	}

	/**
	 * Rotates image specified number of degrees
	 *
	 * @param int $degrees
	 *
	 * @return RokCommon_Image_ImageType_GD
	 * @throws InvalidArgumentException, RuntimeException
	 */
	public function rotateImageNDegrees($degrees, $bgColor = 0)
	{
		if (!is_numeric($degrees)) {
			throw new InvalidArgumentException('$degrees must be numeric');
		}

		if (!function_exists('imagerotate')) {
			throw new RuntimeException('Your version of GD does not support image rotation.');
		}

		$this->workingImage = imagerotate($this->oldImage, $degrees, $bgColor);
		$this->preserveAlpha();

		$newWidth                          = $this->currentDimensions['width'];
		$newHeight                         = $this->currentDimensions['height'];
		$this->oldImage                    = $this->workingImage;
		$this->currentDimensions['width']  = $newWidth;
		$this->currentDimensions['height'] = $newHeight;

		return $this;
	}

	/**
	 * Shows an image
	 *
	 * This function will show the current image by first sending the appropriate header
	 * for the format, and then outputting the image data. If headers have already been sent,
	 * a runtime exception will be thrown
	 *
	 * @param bool $rawData Whether or not the raw image stream should be output
	 *
	 * @return RokCommon_Image_ImageType_GD
	 * @throws RuntimeException
	 */
	public function show($rawData = false)
	{
		$this->preserveAlpha();
		if (headers_sent()) {
			throw new RuntimeException('Cannot show image, headers have already been sent');
		}

		switch ($this->format) {
			case 'GIF':
				if ($rawData === false) {
					header('Content-type: image/gif');
				}
				imagegif($this->oldImage);
				break;
			case 'JPG':
				if ($rawData === false) {
					header('Content-type: image/jpeg');
				}
				imagejpeg($this->oldImage, null, $this->options['jpegQuality']);
				break;
			case 'PNG':
			case 'STRING':
				if ($rawData === false) {
					header('Content-type: image/png');
				}
				imagepng($this->oldImage);
				break;
		}

		return $this;
	}

	/**
	 * Returns the Working Image as a String
	 *
	 * This function is useful for getting the raw image data as a string for storage in
	 * a database, or other similar things.
	 *
	 * @return string
	 */
	public function getImageAsString()
	{
		$data = null;
		ob_start();
		$this->show(true);
		$data = ob_get_contents();
		ob_end_clean();

		return $data;
	}

	/**
	 * Saves an image
	 *
	 * This function will make sure the target directory is writeable, and then save the image.
	 *
	 * If the target directory is not writeable, the function will try to correct the permissions (if allowed, this
	 * is set as an option ($this->options['correctPermissions']).  If the target cannot be made writeable, then a
	 * RuntimeException is thrown.
	 *
	 * TODO: Create additional paramter for color matte when saving images with alpha to non-alpha formats (i.e. PNG => JPG)
	 *
	 * @param string $fileName The full path and filename of the image to save
	 * @param string $format   The format to save the image in (optional, must be one of [GIF,JPG,PNG]
	 *
	 * @return RokCommon_Image_ImageType_GD
	 * @throws InvalidArgumentException, RuntimeException
	 */
	public function save($fileName, $format = null)
	{
		$validFormats = array('GIF', 'JPG', 'PNG');
		$format       = ($format !== null) ? strtoupper($format) : $this->format;

		if (!in_array($format, $validFormats)) {
			throw new InvalidArgumentException ('Invalid format type specified in save function: ' . $format);
		}

		// make sure the directory is writeable
		if (!is_writeable(dirname($fileName))) {
			// try to correct the permissions
			if ($this->options['correctPermissions'] === true) {
				@chmod(dirname($fileName), 0777);

				// throw an exception if not writeable
				if (!is_writeable(dirname($fileName))) {
					throw new RuntimeException ('File is not writeable, and could not correct permissions: ' . $fileName);
				}
			} // throw an exception if not writeable
			else {
				throw new RuntimeException ('File not writeable: ' . $fileName);
			}
		}

		switch ($format) {
			case 'GIF':
				imagegif($this->oldImage, $fileName);
				break;
			case 'JPG':
				imagejpeg($this->oldImage, $fileName, $this->options['jpegQuality']);
				break;
			case 'PNG':
				imagepng($this->oldImage, $fileName);
				break;
		}

		return $this;
	}

	#################################
	# ----- GETTERS / SETTERS ----- #
	#################################

	/**
	 * @return array
	 */
	protected function getOptionDefaults()
	{
		$defaultOptions = array(
			'resizeUp'                 => false,
			'jpegQuality'              => 100,
			'correctPermissions'       => false,
			'preserveAlpha'			=> true,
			'alphaMaskColor'           => array(255, 255, 255),
			'preserveTransparency'     => true,
			'transparencyMaskColor'	=> array(0, 0, 0)
		);
		return $defaultOptions;
	}


	/**
	 * Gets the height of the current image
	 *
	 * @return int the height in pixels of the current image
	 */
	public function getHeight()
	{
		return $this->currentDimensions['height'];
	}

	/**
	 * Gets the width of the current image
	 *
	 * @return int the width of the current image in pixels
	 */
	public function getWidth()
	{
		return $this->currentDimensions['width'];
	}

	#################################
	# ----- UTILITY FUNCTIONS ----- #
	#################################

	/**
	 * Calculates a new width and height for the image based on $this->maxWidth and the provided dimensions
	 *
	 * @return array
	 *
	 * @param int $width
	 * @param int $height
	 */
	protected function calcWidth($width, $height)
	{
		$newWidthPercentage = (100 * $this->maxWidth) / $width;
		$newHeight          = ($height * $newWidthPercentage) / 100;

		return array(
			'newWidth'     => intval($this->maxWidth),
			'newHeight'	=> intval($newHeight)
		);
	}

	/**
	 * Calculates a new width and height for the image based on $this->maxWidth and the provided dimensions
	 *
	 * @return array
	 *
	 * @param int $width
	 * @param int $height
	 */
	protected function calcHeight($width, $height)
	{
		$newHeightPercentage = (100 * $this->maxHeight) / $height;
		$newWidth            = ($width * $newHeightPercentage) / 100;

		return array(
			'newWidth'     => ceil($newWidth),
			'newHeight'	=> ceil($this->maxHeight)
		);
	}

	/**
	 * Calculates a new width and height for the image based on $this->percent and the provided dimensions
	 *
	 * @return array
	 *
	 * @param int $width
	 * @param int $height
	 */
	protected function calcPercent($width, $height)
	{
		$newWidth  = ($width * $this->percent) / 100;
		$newHeight = ($height * $this->percent) / 100;

		return array(
			'newWidth'     => ceil($newWidth),
			'newHeight'	=> ceil($newHeight)
		);
	}

	/**
	 * Calculates the new image dimensions
	 *
	 * These calculations are based on both the provided dimensions and $this->maxWidth and $this->maxHeight
	 *
	 * @param int $width
	 * @param int $height
	 */
	protected function calcImageSize($width, $height)
	{
		$newSize = array(
			'newWidth'     => $width,
			'newHeight'	=> $height
		);

		if ($this->maxWidth > 0) {
			$newSize = $this->calcWidth($width, $height);

			if ($this->maxHeight > 0 && $newSize['newHeight'] > $this->maxHeight) {
				$newSize = $this->calcHeight($newSize['newWidth'], $newSize['newHeight']);
			}
		}

		if ($this->maxHeight > 0) {
			$newSize = $this->calcHeight($width, $height);

			if ($this->maxWidth > 0 && $newSize['newWidth'] > $this->maxWidth) {
				$newSize = $this->calcWidth($newSize['newWidth'], $newSize['newHeight']);
			}
		}

		$this->newDimensions = $newSize;
	}

	/**
	 * Calculates new image dimensions, not allowing the width and height to be less than either the max width or height
	 *
	 * @param int $width
	 * @param int $height
	 */
	protected function calcImageSizeStrict($width, $height)
	{
		$newDimensions = array(
			'newWidth' => 0,
			'newHeight'=> 0
		);
		// first, we need to determine what the longest resize dimension is..
		if ($this->maxWidth >= $this->maxHeight) {
			// and determine the longest original dimension
			if ($width > $height) {
				$newDimensions = $this->calcHeight($width, $height);

				if ($newDimensions['newWidth'] < $this->maxWidth) {
					$newDimensions = $this->calcWidth($width, $height);
				}
			} elseif ($height >= $width) {
				$newDimensions = $this->calcWidth($width, $height);

				if ($newDimensions['newHeight'] < $this->maxHeight) {
					$newDimensions = $this->calcHeight($width, $height);
				}
			}
		} elseif ($this->maxHeight > $this->maxWidth) {
			if ($width >= $height) {
				$newDimensions = $this->calcWidth($width, $height);

				if ($newDimensions['newHeight'] < $this->maxHeight) {
					$newDimensions = $this->calcHeight($width, $height);
				}
			} elseif ($height > $width) {
				$newDimensions = $this->calcHeight($width, $height);

				if ($newDimensions['newWidth'] < $this->maxWidth) {
					$newDimensions = $this->calcWidth($width, $height);
				}
			}
		}

		$this->newDimensions = $newDimensions;
	}

	/**
	 * Calculates new dimensions based on $this->percent and the provided dimensions
	 *
	 * @param int $width
	 * @param int $height
	 */
	protected function calcImageSizePercent($width, $height)
	{
		if ($this->percent > 0) {
			$this->newDimensions = $this->calcPercent($width, $height);
		}
	}

	/**
	 * Determines the file format by mime-type
	 *
	 * This function will throw exceptions for invalid images / mime-types
	 *
	 * @throws RokCommon_Image_Exception
	 */
	protected function determineFormat()
	{
		if ($this->isDataStream === true) {
			$this->format = 'STRING';
			return;
		}

		$formatInfo = getimagesize($this->fileName);

		// non-image files will return false
		if ($formatInfo === false) {
			if ($this->remoteImage) {
				throw new RokCommon_Image_Exception('Could not determine format of remote image: ' . $this->fileName);
			} else {
				throw new RokCommon_Image_Exception('File is not a valid image: ' . $this->fileName);
			}
		}

		$mimeType = isset($formatInfo['mime']) ? $formatInfo['mime'] : null;

		switch ($mimeType) {
			case 'image/gif':
				$this->format = 'GIF';
				break;
			case 'image/jpeg':
				$this->format = 'JPG';
				break;
			case 'image/png':
				$this->format = 'PNG';
				break;
			default:
				throw new RokCommon_Image_Exception('Image format not supported: ' . $mimeType);
		}
	}

	/**
	 * Makes sure the correct GD implementation exists for the file type
	 * @throws RokCommon_Image_Exception
	 */
	protected function verifyFormatCompatiblity()
	{
		$isCompatible = true;
		$gdInfo       = gd_info();

		switch ($this->format) {
			case 'GIF':
				$isCompatible = $gdInfo['GIF Create Support'];
				break;
			case 'JPG':
				$isCompatible = (isset($gdInfo['JPG Support']) || isset($gdInfo['JPEG Support'])) ? true : false;
				break;
			case 'PNG':
				$isCompatible = $gdInfo[$this->format . ' Support'];
				break;
			default:
				$isCompatible = false;
		}

		if (!$isCompatible) {
			// one last check for "JPEG" instead
			$isCompatible = $gdInfo['JPEG Support'];

			if (!$isCompatible) {
				throw new RokCommon_Image_Exception('Your GD installation does not support ' . $this->format . ' image types');
			}
		}
	}

	/**
	 * Preserves the alpha or transparency for PNG and GIF files
	 *
	 * Alpha / transparency will not be preserved if the appropriate options are set to false.
	 * Also, the GIF transparency is pretty skunky (the results aren't awesome), but it works like a
	 * champ... that's the nature of GIFs tho, so no huge surprise.
	 *
	 * This functionality was originally suggested by commenter Aimi (no links / site provided) - Thanks! :)
	 *
	 */
	protected function preserveAlpha()
	{
		if (($this->format == 'PNG' || $this->format == 'STRING') && $this->options['preserveAlpha'] === true) {
			imagealphablending($this->workingImage, false);

			$colorTransparent = imagecolorallocatealpha($this->workingImage, $this->options['alphaMaskColor'][0], $this->options['alphaMaskColor'][1], $this->options['alphaMaskColor'][2], 0);

			imagefill($this->workingImage, 0, 0, $colorTransparent);
			imagesavealpha($this->workingImage, true);
		}
		// preserve transparency in GIFs... this is usually pretty rough tho
		if ($this->format == 'GIF' && $this->options['preserveTransparency'] === true) {
			$colorTransparent = imagecolorallocate($this->workingImage, $this->options['transparencyMaskColor'][0], $this->options['transparencyMaskColor'][1], $this->options['transparencyMaskColor'][2]);

			imagecolortransparent($this->workingImage, $colorTransparent);
			imagetruecolortopalette($this->workingImage, true, 256);
		}
	}
}