29-06-2012, 12:29 PM
Watermarking using wavelets
Watermarking.ppt (Size: 1.47 MB / Downloads: 37)
Electronic publishing
Inexpensive copies
No quality loss
Wide distribution but no control
Now can we protect copyright ?
What is watermarking
Copyright protection methods.
Consists of signing an image with a signature or copyright message.
The message is secretly embedded in the image.
There is no visible difference.
Difficulties
Digital watermarking algorithms usually use the lower-order bit-planes of the original image, so do intentional disturbance algorithms.
Cannot be inserted to downgrade the quality of the source image too much.
Digital watermark readers are usually widely available.
There is a limited amount of data that can be used to insert digital watermarks in a highly compressed JPEG image;
Image compression usually destroy watermarks easily.
Existing methods
Recent frequency domain water-marking methods are based on the discrete cosine trans-form (DCT),where pseudo-random sequences,such as M-sequences, are added to the DCT coefficients at the middle frequencies as signatures.
This approach,of course,matches the current image/video compression standards well,such as JPEG,MPEG 1-2,etc.