Imagick addNoiseImage() Function

The Imagick::addNoiseImage() method is a PHP built-in function for adding noise to a given image. The amount of noise produced is determined by noise constants and channel kinds. The random variation of brightness and contrast in an image is known as image noise.

Syntax:

The following parameters are accepted by this function, as mentioned above and described below:

$noise_type: The noise types are selected using this option. The following are some noise constants available in the Imagick function:
- imagick::NOISE_UNIFORM (int)
- imagick::NOISE_GAUSSIAN (int)
- imagick::NOISE_MULTIPLICATIVEGAUSSIAN (int)
- imagick::NOISE_IMPULSE (int)
- imagick::NOISE_LAPLACIAN (int)
- imagick::NOISE_POISSON (int)
- imagick::NOISE_RANDOM (int)
- This constant is available if Imagick has been compiled against ImageMagick version 6.3.6 or higher.
$channel: The channel constants are provided by this argument. The bitwise operator can be used to combine two or more channels. The following are some of the channel constants available in the Imagick function:
- imagick::CHANNEL_UNDEFINED (int)
- imagick::CHANNEL_RED (int)
- imagick::CHANNEL_GRAY (int)
- imagick::CHANNEL_CYAN (int)
- imagick::CHANNEL_GREEN (int)
- imagick::CHANNEL_MAGENTA (int)
- imagick::CHANNEL_BLUE (int)
- imagick::CHANNEL_YELLOW (int)
- imagick::CHANNEL_ALPHA (int)
- imagick::CHANNEL_OPACITY (int)
- imagick::CHANNEL_MATTE (int)
- imagick::CHANNEL_BLACK (int)
- imagick::CHANNEL_INDEX (int)
- imagick::CHANNEL_ALL (int)
- imagick::CHANNEL_DEFAULT (int)

Return Value

The return type of add noise Image function is of the Boolean type which means the return type of this function will be either a true value or a false value. The return value of this function depends upon the success or failure of the add noise operation. if the addition of noise into the specified image is successful then the return type of this function will be of True Type depicting that the noise is successfully added to our image. on the other hand, if adding noise operation to the image is failed or there is some issue raised due to the wrong parameters specified the return type will be of failure representing an unsuccessful operation of addition of noise to the image.

Example

<?php
/**
 * sCAPTCHA - A simple CAPTCHA generator.
 * 
 */

define('ROOT_DIR', __DIR__);
define('FONT_DIR', __DIR__ . '/fonts/');
define('STORE_DIR', __DIR__ . '/store/');

class sCAPTCHA {

	// configurables (see defaults below)
	private $configurables = array(
			'session', // save generated key on session (boolean)
			'session_name', // session name (string)
			'hash', // hash generated key (boolean)
			'length', // captcha character length
			'table', // characters used in generating random captcha string
			'readable', // use vowels and consonants for captcha readability (boolean)
			'salt', // salt used for hashed key
			'font', // font name
			'height', // captcha image height
			'width', // captcha image width
			'wave', // wave effect, amplitude and length (array)
			'swirl', // swirl effect (integer)
			'noise', // add (effect) background noise (boolean)
			'custom_font', // use custom font instead of the default one (boolean)
			'custom_font_name', // custom font name
			'font_size', // font size
			'format', // file format (png, jpeg, or gif)
			'store', // store generated image to a file (boolean)
			'store_path' // where to store generated image
		);

	// Colors from http://www.imagemagick.org/script/color.php
	private $color_table = array(
			'#FF0000', // red		
			'#0000FF', // blue
			'#008000', // green
			'#000000' // black
		);

	private $format_table = array(
			'png', // PNG
			'jpeg', // JPEG
			'jpg', // JPEG
			'gif' // GIF
		);

	// set default configurations
	private $session = false;
	private $session_name = 'sCAPTCHA';
	private $hash = true;
	private $salt = null; // salt used for hashed key (default none)
	private $length = 5;
	private $table = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
	private $readable = true;
	private $noise = false;
	private $custom_font = false;
	private $custom_font_name = 'Moms_typewriter.ttf'; // default custom font
	private $font = 'Arial'; // default font
	private $font_size = 35; // default font size

	// captcha image default size
	private $width = 200;
	private $height = 57;

	// text/image effects
	private $swirl = 10;
	private $wave = array(
			'amplitude' => 5,
			'length' => 50
		);
	private $noise_type = 3;
	private $noise_channel = 3;

	// generated key store
	private $key = null;

	// default image format
	private $format = 'png';
	private $store = false;
	private $store_path = STORE_DIR;

	// instantiate
	public function __construct() {
		// set additional default variables
		$this->wave_default = $this->wave;
		$this->format_default = $this->format;
		$this->store_path_default = STORE_DIR;
	}

	// override default configuration
	public function config($config = null) {
		if (isset($config) && is_array($config)) {
			foreach ($config as $k => $v) {
				if (in_array($k, $this->configurables) && isset($v)) {
					$this->$k = $v;
				}
			}
		}
	}

	// generate random key based on the character table
	public function key() {

		if ($this->readable) {
			$this->key = $this->easyRead();
		} else {
			for ($i = 0; $i <= $this->length; $i++) {
				$this->key .= $this->table{rand(0, (strlen($this->table) - 1))};
			}
		}

		// check if to use session to save generated key
		if ($this->session) {
			// check if session is enabled, if not start session
			if(session_id() == "") {
				session_start();
				// check if generated key need to be hashed
				if ($this->hash) {
					$_SESSION[$this->session_name] = sha1($this->key . $this->salt);
				} else {
					$_SESSION[$this->session_name] = $this->key;
				}
			}
		}

		return $this->key;
	}

	// generate readable challenge string
	// based from http://www.phpsnippets.info/generate-a-password-in-php
	public function easyRead() {
		$vowels = 'aeuyAEUY';
		$consonants = 'bdghjmnpqrstvzBDGHJLMNPQRSTVWXZ';

		$string = '';
		$alt = time() % 2;
		for ($i = 0; $i < $this->length; $i++) {
			if ($alt == 1) {
				$string .= $consonants[(rand() % strlen($consonants))];
				$alt = 0;
			} else {
				$string .= $vowels[(rand() % strlen($vowels))];
				$alt = 1;
			}
		}

		return $string;
	}

	// generate captcha image
	public function captcha() {

		// get generated characters
		if (!is_null($this->key) && isset($this->key)) {
			$text = $this->key;
		} else {
			$text = $this->key(); // generate key
		}

		// create Imagick objects
		$image = new Imagick();
		$draw = new ImagickDraw();

		$font_color = new ImagickPixel($this->color_table{rand(0, (count($this->color_table) - 1))});
		$background = new ImagickPixel('#ffffff'); // white

		// font properties
		if (!$this->custom_font) {
			$draw->setFont($this->font);
		} else {
			// check if custom font file exists
			if (file_exists(FONT_DIR . $this->custom_font_name)) {
				$draw->setFont(FONT_DIR . $this->custom_font_name);
			} else {
				$draw->setFont($this->font); // fallback to the default font
			}
		}

		$draw->setFontSize($this->font_size);
		$draw->setFillColor($font_color);

		// get font metrics for centering text string
		$fm = $image->queryFontMetrics($draw, $text, false);
		$coordinate_x = ($this->width / 2) - ($fm["textWidth"] / 2);
		$coordinate_y = $this->height - ($fm["textHeight"] / 2);

		// create text
		$draw->annotation($coordinate_x, $coordinate_y, $text);

		// create image
		$image->newImage($this->width, $this->height, $background);

		// check if file/image format is valid
		$format_setting = strtolower($this->format);
		if (in_array($format_setting, $this->format_table)) {
			if ($format_setting == 'jpeg') {
				$format_setting = 'jpg';
			}
			$image_format = $format_setting;
		} else {
			$image_format = $this->format_default; // fallback to the default file/image format
		}

		$image->setImageFormat($image_format);
		$image->drawImage($draw);

		// add image effects

		// wave
		if (is_array($this->wave)) {
			$image->waveImage($this->wave['amplitude'], $this->wave['length']);
		} else {
			$image->waveImage($this->wave_default['amplitude'], $this->wave_default['length']);
		}

		// swirl
		$image->swirlImage($this->swirl);

		// background noise
		if ($this->noise) {
			$image->addNoiseImage($this->noise_type, $this->noise_channel);
		}

		// check if generated image will be saved as a file
		if ($this->store) {
			$filename = md5(time()) . '.' . $image_format; // construct file's name

			// check if directory exists
			if (file_exists($this->store_path)) {
				$store_file_path = rtrim($this->store_path, '/') . '/' . $filename;
			} elseif (file_exists($this->store_path_default)) { // try the default store path
				$store_file_path = rtrim($this->store_path_default, '/') . '/' . $filename;
			} else {
				// try creating the default store path
				if (!mkdir(rtrim($this->store_path_default, '/'))) {
					return false;
				}
				$store_file_path = rtrim($this->store_path_default, '/') . '/' . $filename;
			}

			// store/save image file
			file_put_contents($store_file_path, $image);
			
			return $filename; // return only the file's name

		} else {
			// return generated image
			return $image;
		}

	}

}

Output:

The example that is written above shows us one of the use case scenarios of the add noise Image function provided by PHP. in this example the at noise Image function is used to create the captcha image this captcha image is made by adding deliberate noise with the help of this function. the captcha images are used broadly across the internet these days to verify the differentiation between the humans and robots accessing various websites throughout the internet.

Example2:

 /**
  * Creates image with text
  * @param int $sizeX
  * @param int $sizeY
  * @param string $text
  * @param string $generator
  * @return \Imagick
  */
 public function mkCapcha($sizeX, $sizeY, $text, $generator = self::METHOD_DEFAULT)
 {
     // init image
     $image = new \Imagick();
     $image->newImage($sizeX, $sizeY, new \ImagickPixel('white'));
     $image->setImageFormat('png');
     switch ($generator) {
         case self::METHOD_GRAYNOISE:
             $draw = new \ImagickDraw();
             $draw->setFontSize(35);
             $draw->setFontWeight(900);
             $draw->setGravity(\imagick::GRAVITY_CENTER);
             $image->addNoiseImage(\imagick::NOISE_LAPLACIAN);
             $image->annotateImage($draw, 0, 0, 0, $text);
             $image->charcoalImage(2, 1.5);
             $image->addNoiseImage(\imagick::NOISE_LAPLACIAN);
             $image->gaussianBlurImage(1, 1);
             break;
         case self::METHOD_GRAYBLUR:
             $draw = new \ImagickDraw();
             $order = [];
             for ($i = 0; $i < strlen($text); $i++) {
                 $order[$i] = $i;
             }
             shuffle($order);
             for ($j = 0; $j < 2; $j++) {
                 shuffle($order);
                 $image->gaussianBlurImage(15, 3);
                 for ($n = 0; $n < strlen($text); $n++) {
                     $i = $order[$n];
                     $draw->setFont(__DIR__ . '/Capcha/DejaVuSans.ttf');
                     $draw->setFontSize($j ? rand($sizeY * 3 / 5, $sizeY * 5 / 6) : rand($sizeY * 4 / 6, $sizeY * 5 / 6));
                     $draw->setFontWeight(rand(100, 900));
                     $draw->setGravity(\imagick::GRAVITY_CENTER);
                     $image->annotateImage($draw, ($i - strlen($text) / 2) * $sizeX / (strlen($text) + 2.3), 0, rand(-25, 25), $text[$i]);
                     $image->gaussianBlurImage(1, 1);
                 }
             }
             break;
     }
     return $image;
 }

Output:

This is another example that depicts the use case scenario of add noise Image function in PHP. in this example we have added deliberate noise to any image with the help of this function in this function we have to use different methods like method grey-blue and method grey noise with the help of these parameters we can control the type and quantity of the noise that we are introducing to an image.

In this article, we have gone through the use case scenario of add noise Image function provided by PHP and have understood the usage and different parameters that are passed to this function and how we can use this function with different sets of parameters that are available to manipulate the type, quantity, and precision of the noise that we are introducing to the image.

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