my project is on digital color image watermarking . after embedding a watermark when i calculate psnr of original and watermarked image the calculated value that i receive is 104.76 . I don't understand is this value is good or bad???

my project is on digital color image watermarking . after embedding a watermark when i calculate psnr of original and watermarked images the calculated value that i receive is 104.76 . I don't know is this value is good or bad???

Answer 1

[Walter Roberson]

Provided you calculated it properly, it is good. See http://en.wikipedia.org/wiki/Peak_signal-to-noise_ratio

Typical values for the PSNR in lossy image and video compression are between 30 and 50 dB, provided the bit depth is 8 bits, where higher is better.

For comparison, suppose you had a 512 x 512 x 3 RGB uint8 image, and suppose in exactly 2 places in that array you changed the value by only 1 (e.g., a component was 145 and you changed it to 146.) Don't change a single location by 2 in this discussion, change two different locations by 1 each. Then in that case, the calculated PSNR would be 104.08, which is below what you got. So you must be using a larger image.

For example if your image was 512 x 600 x 3, uint8, then a change of 1 in two different places would lead to a PSNR of 104.7659. That indicates that little was changed.