Hidden Watermark

Embeds a hidden watermark in an image using a blind DWT-DCT approach. Unlike steganographic methods, this hidden watermark is resistant to various forms of attack. Limited to a black and white 32x32 watermark image.

Original Image + Watermark = Watermarked Image

+ =

Image source: http://commons.wikimedia.org/wiki/Garden#/media/File:Rikugien3.jpg

Usage

The following code instantiates the default watermark class with the default watermark image. Then the watermark is embedded in a file, and the watermark is retrieved afterwards.

var fileBytes = File.ReadAllBytes(imageLocation);
var newFileBytes = Watermark.Default.EmbedWatermark(fileBytes);

var result = Watermark.Default.RetrieveWatermark(newFileBytes);

The following code instantiates the watermark class with the bytes read from a 32x32 watermark image and turns crop support on. Then the watermark is embedded in a file and simultaneously checked if an embedded watermark already exists.

var watermarkBytes = File.ReadAllBytes(watermarkLocation);
Watermark watermark = new Watermark(watermarkBytes, true);

var fileBytes = File.ReadAllBytes(imageLocation);
var result = watermark.RetrieveAndEmbedWatermark(fileBytes);

Watermark recovery results

Attack	Recovered Watermark
No Attack
Blur
Flip Horizontal
Resize (1024x768->360x270)
Visible Watermarking
Crop
JPEG Quality 20%
Grayscale	(not resistant)
PrintScreen
Noise

Acknowledgements

Accord.NET: http://accord-framework.net/