**5. Non-blind watermarking**

Another watermarking method operating upon significant coefficients within the wavelet domain was presented by Miyazaki et al. [9]. This method takes a threelevel wavelet transform of the image to be watermarked and inserts the watermark

into the detail coefficients at the coarsest scales (LH3, HL3); the low-pass component LL3 and diagonal details HH3 are excluded.

### **5.1 Miyazaki's method**

Two watermarking algorithms were presented by Miyazaki et al. [9]. Both algorithms were implemented in the wavelet domain, but each targeted a different set of coefficients for insertion. The first of these insertion methods is applied on insignificant coefficients, whereas the second type of insertion is applied on significant coefficients. So, both insertion techniques would be applied to a single image at the same time. However, experimental results proved that the insertion method by applying the significant coefficients was more robust than the insertion method using insignificant coefficients. So, the insertion method utilizing the significant coefficients will be considered.

This thesis introduces a new quantization-based, blind watermarking algorithm operating in the wavelet domain. This algorithm has several advantages as compared to previously published algorithms. For example, the proposed algorithm is better than the algorithm of Dugad in its ability to survive the same malicious attacks while producing marked images of greater visual quality. The proposed watermarking scheme is a blind scheme not requiring a file containing the positions

The proposed watermarking scheme is a blind quantization-based scheme. A

2. Then the coefficients in the third level (except the LL3 and HH3 sub-bands) which have magnitude higher than t1 and lower than t2 are chosen to hide in. Let be the wavelet coefficient with maximum absolute in both HL3 and LH3

3. Then the binary watermark is created using a secret key, which is a seed of a random generator; the watermark size should be of the same size as the two

0*:*01< α<0*:*1 and t2>t1>t*:* (6)

1. The cover image is decomposed into sub-bands using three levels of

sub-bands. A threshold t = α is selected, as mentioned in Eq. (6):

4.Then apply quantization to each of the selected wavelet coefficients.

Daubechies wavelet transform using filters of length 4.

of the marked coefficients as in the method of Miyazaki.

block diagram detailing its steps is shown in **Figure 1**.

sub-bands which are selected for embedding.

**6. The proposed watermarking scheme**

*Blind Wavelet-Based Image Watermarking DOI: http://dx.doi.org/10.5772/intechopen.88131*

**6.1 Watermark embedding**

**Figure 1.**

**103**

*The proposed image watermarking scheme.*

In this technique three-level wavelet transform is applied to the image, and the watermark is inserted into the detail coefficients at the wavelet level three. The detailed coefficients which are found at level three are the horizontal details, High Low 3 (HL3); the vertical details, Low High 3 (LH3); and the diagonal details, High High 3 (HH3). The low-pass component, Low Low 3 (LL3), is left unchanged. This is a quantization-based watermarking method which aims to modify wavelet coefficients of high magnitude, thus embedding the watermark into edge and textured regions of an image. The process for watermark insertion is as follows:

#### *5.1.1 Embedding algorithm*


If Wat(k) = 1 and Cok > 0, then Cok = t2, If Wat(k) = 0 and Cok > 0, then Cok = t1, If Wat(k) = 1 and Cok < 0, then Cok = t2, If Wat(k) = 0 and Cok < 0, then Cok = t1,

4.The embedded position, sub-band label, and the two thresholds t1 and t2 should be saved.

#### *5.1.2 Detection algorithm*

The following process details the steps involved for watermark detection:


If Cok < (t1 + t2) /2, then the recovered watermark bit is 0. If Cok ≥ (t1 + t2) /2, then the recovered watermark bit is 1.

*Blind Wavelet-Based Image Watermarking DOI: http://dx.doi.org/10.5772/intechopen.88131*

into the detail coefficients at the coarsest scales (LH3, HL3); the low-pass

Two watermarking algorithms were presented by Miyazaki et al. [9]. Both algorithms were implemented in the wavelet domain, but each targeted a different set of coefficients for insertion. The first of these insertion methods is applied on insignificant coefficients, whereas the second type of insertion is applied on significant coefficients. So, both insertion techniques would be applied to a single image at the same time. However, experimental results proved that the insertion method by applying the significant coefficients was more robust than the insertion method using insignificant coefficients. So, the insertion method utilizing the significant

In this technique three-level wavelet transform is applied to the image, and the watermark is inserted into the detail coefficients at the wavelet level three. The detailed coefficients which are found at level three are the horizontal details, High Low 3 (HL3); the vertical details, Low High 3 (LH3); and the diagonal details, High High 3 (HH3). The low-pass component, Low Low 3 (LL3), is left unchanged. This is a quantization-based watermarking method which aims to modify wavelet coefficients of high magnitude, thus embedding the watermark into edge and textured

1. Two thresholds, t1 and t2, are selected, and any one of the sub-bands LH3 and HL3 is chosen. Next, significant coefficients Cok (k = 1, 2… N) satisfying t1

3. For k = 1, 2,… N, the embedding of the watermark is applied by modifying Ck

4.The embedded position, sub-band label, and the two thresholds t1 and t2

The following process details the steps involved for watermark detection:

If Cok < (t1 + t2) /2, then the recovered watermark bit is 0. If Cok ≥ (t1 + t2) /2, then the recovered watermark bit is 1.

1. Using the sub-band label and the embedded position, the recovered wavelet

regions of an image. The process for watermark insertion is as follows:

2. A binary watermark is created, Wat (k); k = 1, 2… N.

If Wat(k) = 1 and Cok > 0, then Cok = t2, If Wat(k) = 0 and Cok > 0, then Cok = t1, If Wat(k) = 1 and Cok < 0, then Cok = t2, If Wat(k) = 0 and Cok < 0, then Cok = t1,

coefficients Cok. k = 1, 2… N are obtained.

component LL3 and diagonal details HH3 are excluded.

**5.1 Miyazaki's method**

*Cyberspace*

coefficients will be considered.

*5.1.1 Embedding algorithm*

as follows:

should be saved.

2. Check each Ck individually:

*5.1.2 Detection algorithm*

**102**

< Cok < t2 are found.

This thesis introduces a new quantization-based, blind watermarking algorithm operating in the wavelet domain. This algorithm has several advantages as compared to previously published algorithms. For example, the proposed algorithm is better than the algorithm of Dugad in its ability to survive the same malicious attacks while producing marked images of greater visual quality. The proposed watermarking scheme is a blind scheme not requiring a file containing the positions of the marked coefficients as in the method of Miyazaki.
