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
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);| Attack | Recovered Watermark |
|---|---|
| No Attack |  |
| Blur |  |
| Flip Horizontal |  |
| Resize (1024x768->360x270) |  |
| Visible Watermarking |  |
| Crop |  |
| JPEG Quality 20% |  |
| Grayscale |  (not resistant) |
| PrintScreen |  |
| Noise |  |
Accord.NET: http://accord-framework.net/