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phpimage-processingimagemagickimagick

how to restore the watermark set with Imagick::steganoImage()

So I used this Imagemagick library wrapper written in PHP and came to know about this function called steganoImage() which simply says that it will hide a watermark inside the image. But problem is documentation doesn't state how to restore that image back. I checked all the other functions too, didn't find anything. I would like to have an Imagick solution for this.

Solution

  • The answer provided by Bonzo is correct. An example in PHP's Imagick would look very similar.

    $image = new Imagick('rose:');
$watermark = new Imagick('label:Hello World!');

// The decoding process must "know" about the watermarks size, and starting
// pixel offset.
define('STEGANO_OFFSET', 64); // Secret offset
define('STEGANO_WIDTH', $watermark->getImageWidth());
define('STEGANO_HEIGHT', $watermark->getImageHeight());

$stegano = $image->steganoImage($watermark, STEGANO_OFFSET);
$stegano->writeImage('output.png');

    output.png

    To decode the original watermark, define the width, height, and offset of the hidden image before reading the file.

    $decoded = new Imagick();
$decoded->setSizeOffset(STEGANO_WIDTH, STEGANO_HEIGHT, STEGANO_OFFSET);
$decoded->readImage('STEGANO:output.png');
$decoded->writeImage('decoded.png');

    decoded.png