“…The PSNR of the reconstructed image is used to measure the invisibility of the image (watermark carrier data) after embedding the watermark,
32 which is calculated as follows:
where
is the number of bits per sampled value,
is the mean square error between the original image and the processed image,
and
denote the numbers of image pixel size,
is the pixel point in the i th row and j th column of the original image (watermark carrier data), and
is the pixel point in the i th row and j th column of the reconstructed image (reconstructed image). The higher the PSNR, the clearer the reconstructed image.…”