B. Metadata Hiding
The embedding is performed in DCT domain using 8x8
blocks by quantizing the DCT coefficients of image blocks. We
select the low frequency coefficients in every image block to
form a vector of host signal where we will embed the QR code
bits. We embed the QR code bits with rate 0.2, means we
embed 1 watermark bit into 5 coefficients. Then we generate a
random spread vector with the same dimension as host-signal
vector and normalize it. After that we quantize the projection of
host-signal vector to spread vector based on the QR code bits
using uniform scalar quantizer.