Lossless data embedding with file size preservation

In lossless watermarking, it is possible to completely remove the embedding distortion from the watermarked image and recover an exact copy of the original unwatermarked image. Lossless watermarks found applications in fragile authentication, integrity protection, and metadata embedding. It is especially important for medical and military images. Frequently, lossless embedding disproportionably increases the file size for image formats that contain lossless compression (RLE BMP, GIF, JPEG, PNG, etc...). This partially negates the advantage of embedding information as opposed to appending it. In this paper, we introduce lossless watermarking techniques that preserve the file size. The formats addressed are RLE encoded bitmaps and sequentially encoded JPEG images. The lossless embedding for the RLE BMP format is designed in such a manner to guarantee that the message extraction and original image reconstruction is insensitive to different RLE encoders, image palette reshuffling, as well as to removing or adding duplicate palette colors. The performance of both methods is demonstrated on test images by showing the capacity, distortion, and embedding rate. The proposed methods are the first examples of lossless embedding methods that preserve the file size for image formats that use lossless compression.