/**
* Merge captcha image with background
*
* @param int $width: width of the image in pixels
* @param int $height: width of the image in pixels
* @param string $captchaImage: a GD image identifier
* @param string $backgroundImage: a GD image identifier
* @param string $backgroundType (see constants)
* @param int $mergeType: 0 - Background over captcha, 1 - Captcha over background (see constants)
* @param int $backgroundFadePercentage: fading factor for background
* @return string GD image identifier of merged image
*/
public static function mergeCaptchaWithBackground($width, $height, $captchaImage, $backgroundImage, $backgroundType, $mergeType)
{
if ($backgroundType != self::BACKGROUND_TYPE_TRANSPARENT) {
// How faded should the background be? (100=totally gone, 0=bright as the day)
// to test how much protection the bg noise gives, take a screenshot of the freeCap image
// and take it into a photo editor. play with contrast and brightness.
// If you can remove most of the background, then it's not a good enough percentage
switch ($backgroundType) {
case self::BACKGROUND_TYPE_WHITE_WITH_GRID:
case self::BACKGROUND_TYPE_WHITE_WITH_SQUIGGLES:
$backgroundFadePercentage = 65;
break;
case self::BACKGROUND_TYPE_MORPHED_IMAGE_BLOCKS:
$backgroundFadePercentage = 50;
break;
}
// Slightly randomize the background fade
$backgroundFadePercentage += RandomContentUtility::getRandomNumberInRange(-2, 2);
// Fade background
if ($backgroundType != self::BACKGROUND_TYPE_MORPHED_IMAGE_BLOCKS) {
$tempImage = ImageCreateTrueColor($width, $height);
$white = ImageColorAllocate($tempImage, 255, 255, 255);
ImageFill($tempImage, 0, 0, $white);
ImageCopyMerge($backgroundImage, $tempImage, 0, 0, 0, 0, $width, $height, $backgroundFadePercentage);
ImageDestroy($tempImage);
$colorFadePercentage = 50;
} else {
$colorFadePercentage = $backgroundFadePercentage;
}
// Merge background image with CAPTCHA image to create smooth background
if ($mergeType == self::MERGE_CAPTCHA_OVER_BACKGROUND) {
// Might want to not blur if using this method, otherwise leaves white-ish border around each letter
ImageCopyMerge($backgroundImage, $captchaImage, 0, 0, 0, 0, $width, $height, 100);
ImageCopy($captchaImage, $backgroundImage, 0, 0, 0, 0, $width, $height);
} else {
// Background over captcha
ImageCopyMerge($captchaImage, $backgroundImage, 0, 0, 0, 0, $width, $height, $colorFadePercentage);
}
}
return $captchaImage;
}
