PngWatermarker
PngWatermarker is a .NET 4.5+ library for the embedding and extraction of invisible watermarks on PNG files.
It makes use of the lovely pngcs library for decoding/encoding of the PNG files, the library was written by Hernán J. González, which is available here: https://code.google.com/p/pngcs/
Features
- Embed various watermarks into PNG files
- Extract the watermarks at a later time
- A watermarked image is almost impossible to distinguish.
- Clever embedding process ensures the watermark is not stored in a sequential pattern
Watermark Types
Basic
- Text Watermark
- Allows for the storage of a String.
- File Watermark
- Allows for the storage of a file, preserving the original extension.
- Binary Watermark
- Allows for the storage of binary data.
Advanced
- Composite Watermark
- Allows for the storage of 1 to many basic watermarks as a single watermark in the image.
- Encrypted Watermark
- Allows for the encryption and storage of any watermark (except other Encrypted Watermarks).
- Encryption is performed by any SymmetricAlgorithm subclass.
Examples
Text Watermark
PNGFile file = new PNGFile("MyOriginal.png");
TextWatermark mark = new TextWatermark("This is a text based watermark");
Watermarker.EmbedWatermark(file,mark,"password","MyOutput.png");
//Extraction
file = new PNGFile("MyOutput.png");
TextWatermark extract = (TextWatermark)Watermarker.ExtractWatermark(file,"password");
Composite Watermark
PNGFile file = new PNGFile("MyOriginal.png");
CompositeWatermark comp = new CompositeWatermark();
FileWatermark fileMark = new FileWatermark("MyFile.txt");
BinaryWatermark binMark = new BinaryWatermark(new byte[]{1,2,3,4});
comp.AddWatermark(fileMark);
comp.AddWatermark(binMark);
Watermarker.EmbedWatermark(file,comp,"password","MyOutput.png");
//Extraction
PNGFile file2 = new PNGFile("MyOutput.png");
CompositeWatermark extract = (CompositeWatermark)Watermarker.ExtractWatermark(file2,"password");
Watermark[] marks = extract.GetWatermarks();
Encrypted Watermark
PNGFile file = new PNGFile("MyOriginal.png");
RijndaelManaged aes = new RijndaelManaged();
aes.Padding = PaddingMode.Zeroes;
EncryptedWatermark.Algorithm = aes;
TextWatermark mark = new TextWatermark("This should be encrypted");
EncryptedWatermark encrypted = new EncryptedWatermark(mark, "super-secret");
Watermarker.EmbedWatermark(file, encrypted, "password", "MyOutput.png");
PNGFile file2 = new PNGFile("MyOutput.png");
EncryptedWatermark extract = Watermarker.ExtractWatermark(file2, "password");
extract.Decrypt("super-secret");
Watermark decrypted = extract.DecryptedMark;
Original File
File holding a watermark
