Table 3 Comparing the structures of D. Asatryan and N. Asatryan [27], Mahanty and Bhargava [24], and proposed watermarking methods.

Block size of original image

Mohanty's method [24]

Asatryan's method [27]

Proposed method

Selection embedding area procedure

(1) Find a most perceptually significant set of blocks constituting a subimage (equal to size of watermark) with respect to human perception such as Texture, Location, Contrast, Luminance, and Edginess in original image.

(1) All blocks of original image are used to embed a watermark

(1) Calculate the Texture, Luminance, and Location of each DCT block in original image.

(2) Use proposed Fuzzy Interface System to calculate the suitabilityfactor of each block.

(3) Select () blocks with higher suitability factor to embed a watermark.

Block size of watermark

Watermark creation procedure

(2) Create synthetic image by using DCT coefficients of most perceptually important subimage of original image and Gaussian/Laplacian distribution for DC, AC coefficients, respectively.

(3) Embed the watermark in the synthetic image using any DCT-based visible watermarking algorithm.

(2) Compression was performed on watermark image until the number of chosen DCT coefficients of each 32×32 DCT block was significantly smaller than the number of pixels of the original watermark.

(3) The values of DCT coefficients are mapped to the interval [0,255] by fixed linear transform.

(4) Change the AC coefficients of each DCT block to zero and apply IDCT to create used watermark.

Inserting procedure

(4) The used watermark is now invisibly embedded into the original image by fusing the compound watermark blocks with the corresponding blocks of the selected perceptually important subimage of the original.

(4) Embed each mapped DCT coefficient of watermark in each pixel of block of original image.

(5) Embed DC coefficient of each DCT block of used watermark in DC coefficient of selected DCT block of original image.

Value of β coefficient (weighing factor)

for all pixels

is different for each DCT block of original image and is computed by proposed Fuzzy Interface System based on Texture and Luminance of selected block.

Extracting procedure

(1) Select subimage of original image where the watermark was embedded in it.

(2) Use the reverse embedding procedure to extract the DCT coefficients of watermark.

(3) Apply IDCT on each extracted DCT block to create watermark in spatial domain.

(1) Use the reverse embedding procedure to extract the mapped DCT coefficients of watermark.

(2) The reverse of linear transform where used in embedding process is utilized to create the DCT coefficients of watermark.

(3) Apply IDCT on each extracted DCT block to create watermark in spatial domain.

(1) Select blocks of original image where the watermark was embedded in them.

(2) Use the reverse embedding procedure to extract the DC coefficients of each DCT block of used watermark.

(3) The extracted DC coefficients are used to estimate the AC coefficients of each DCT block of watermark.

(4) Apply IDCT on each estimated DCT block to create watermark in spatial domain.