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<?php
/**
 * @file
 *   Helper class for encoding images as Base64.
 *   Has support for the Drupal module ImageCache, just provide it with your
 *   preset name if you'd like the class to use that version of an image instead.
 *   Is by no means dependent on Drupal though. Just a nice feature.
 *   Feel free to use it as you like.
 *
 * @author Simon Ljungberg <simon@nimnim.se>
 */

/**
 * Error code definitions.
 * Defined outside the class to make them available to the user of the class.
 */
define('B64IMG_FILE_NOT_FOUND_ERROR', 1);
define('B64IMG_FILE_READ_ERROR', 2);
define('B64IMG_IMAGECACHE_PRESET_NOT_FOUND', 4);
define('B64IMG_IMAGECACHE_FAILED', 8);
define('B64IMG_IMAGECACHE_NOT_FOUND', 16);

class Base64Image {

  /**
   * The base64 encoded image string
   * @var string
   * @access private
   */
  private $base64;

  /**
   * Base64 encodes an image and returns the result.
   *
   * Useful when you need to save an image using a JavaScript client etc.
   *
   * @param string $imageFile
   *   Path to the image.
   * @param stirng $imageMIME
   *   Image MIME type.
   * @param string $imageCachePreset
   *   An image cache preset name, optional.
   * @return string $base64Image
   * @throws Exception
   *   Throws an exception if the file cannot be found.
   */
  public function __construct($imageFile, $imageMIME, $imageCachePreset = FALSE) {
    // Make sure the image exists
    if (!file_exists($imageFile)) {
      throw new Exception('File not found: ' . $imageFile, B64IMG_FILE_NOT_FOUND_ERROR);
    }

    // All strings begin with this sequence, that way they can be used
    // directly in an image tag.
    $this->base64 = 'data:' . $imageMIME . ';base64,' . "\r\n";

    // Add the encoded image
    $this->base64 .= ($imageCachePreset) ? $this->encodeImageCache($imageFile, $imageCachePreset) : $this->encodeImage($imageFile);
  }

  /**
   * Encodes an image.
   *
   * @access private
   * @param string $imageFile
   * @return string $encodedFile
   * @throws Exception
   *   Throws an exception is if a read error occur.
   */
  private function encodeImage($file) {
      $imgbinary = fread(fopen($file, 'r'), filesize($file));
      if (!$imgbinary) {
        throw new Exception('Could not read image: ' . $file, B64IMG_FILE_READ_ERROR);
      }
      return chunk_split(base64_encode($imgbinary), 64);
  }

  /**
   * Encode an ImageCache image.
   *
   * @access private
   * @param string $imageFile
   * @param string $imageCachePreset
   * @return string $encodedFile
   * @throws Exception
   *   Throws an exception is if a read error occur.
   */
  private function encodeImageCache($file, $preset) {
    // Make sure we have the module
    if (!function_exists('imagecache_build_derivative')) {
      throw new Exception('ImageCache module does not seem to be installed.', B64IMG_IMAGECACHE_NOT_FOUND);
    }

    // Validate the image preset
    $p = imagecache_preset_by_name($preset);
    if (empty($p)) {
      throw new Exception('No ImageCache preset with name ' . $preset . ' could be found', B64IMG_IMAGECACHE_PRESET_NOT_FOUND);
    }

    // Construct an imagecache path
    $imagepath = imagecache_create_path($preset, $file);

    // Seems like the first time this image is accessed, create it
    if (!file_exists($imageapth)) {
      $builtImage = imagecache_build_derivative($p['actions'], $file, $imagepath);
      if (!$builtImage) {
        throw new Exception('Failed to build ImageCache image.', B64IMG_IMAGECACHE_FAILED);
      }
    }

    // We should now have the image, encode it using our other method
    return $this->encodeImage($imagepath);
  }

  /**
   * Return the string representation of the image.
   */
  public function __toString() {
    return $this->base64;
  }
}