Watermarking refers to hiding a message within an image or signal; it can be a video also. An image is used as a cover to hide the message which is intended for transfer. Now-a-days, digital watermarking is used in various applications. Watermarking is mainly used for security purposes. Level of threats faced by watermarking depends on the application area. The properties of a good watermark should include robustness and imperceptibility.

1. REVERSIBLE COLOR IMAGE
WATERMARKING
NADARAJAN A
MARIAN COLLEGE,KUTTIKKANAM

2. CONTENTS
• Introduction
• Reversible watermarking
• Watermark Embedding
• Watermark Extraction
• Example
• Conclusion
• References 2

3. DIGITAL WATERMARKING
• Digital information (watermark) embedded within any
multimedia object that can be later detected and
extracted for object assertion purposes
3
Host image watermarked
image

4. DIGITAL WATERMARKING PROCESS
4
Embedding unit
Watermarked
object
Attack
cover
object
Extraction unit watermark
watermark

5. REVERSIBLE WATERMARKING
• Watermarking schemes which can
recover the original image from the
watermark extracted image
5

6. REVERSIBLE COLOR IMAGE
WATERMARKING USING TRIGONOMETRIC
FUNCTIONS
 Embeds secret bits into the gray planes of the
color image
 Using interpolation method and trigonometric
functions
6

7. WATERMARKING PROCESS
7
Cover l image
Extended cover image
Modified image
Watermarked image
Embedded
values
Bit stream
recovered
Recovered
watermark
interpolation
Watermark Trignometrical
function

8. REVERSIBLE COLOR IMAGE WATERMARKING
USING TRIGONOMETRIC FUNCTIONS
Embedding process
Step 1: Original image is read and divided into multiple 2x2 blocks
Step 2: Each 2x2 blocks converted into 3x3 blocks using interpolation
Step 3: The values of newly inserted elements are changed using the
trigonometric functions
Step 4: Logarithmic values of these new elements are taken and stored
in a variable
Step 5: Bit stream chosen according to log values
Step 6: Decimal values of those bit streams are embedded in the new
elements of 3×3 blocks
8

9. REVERSIBLE COLOR IMAGE WATERMARKING USING
TRIGONOMETRIC FUNCTIONS
Extraction process
Step 1: Watermarked image is divided into 3×3 blocks
Step 2: Embedded values are extracted from the watermarked image
Step 3: Embedded bit stream is recovered using trigonometric functions
9

10. REVERSIBLE COLOR IMAGE WATERMARKING USING
TRIGONOMETRIC FUNCTIONS
I - original image (cover image)
C - interpolated image
Each 2×2 block in I is converted into 3×3 block using the following
formulas:
C(1,1) = I(1,1)
C(1,3) = I(1,2)
C(3,1) = I(2,1)
C(3,3) = I(2,2)
10

11. INTERPOLATION
11
   
   
   
   
   
2
)3,3()1,3(
)2,3(
2
)3,3()3,1(
)3,2(
2
)2,3()2,1(
)2,2(
2
)1,3()1,1(
)1,2(
2
)3,1()1,1(
)2,1(
22
22
22
22
22
CC
C
CC
C
CC
C
CC
C
CC
C











12. TRIGONOMETRIC FUNCTIONS
12
 
 
2
)1,3()1,1(
cos2)1,2()1,2(
2
)3,1()1,1(
cos2)2,1()2,1(
CC
CC
CC
CC





13. 15 0
220 255
15 10 0
155 167 180
220 238 255
15 11 0
155 168 180
220 240 255
15 12 0
155 168 180
220 243 255
interpolation
Trigonometric
function
watermark
embedding
10011
Watermark embedding
13

14. 14
Cover image Watermarked image
Watermarked Lena Image

15. image Image format Image size PSNR between original
image(blue plane) vs.
watermarked image
PSNR between original
image(green plane)
vs.watermarked image
Lena
.jpg
100 x100 56.3520 49.7664
128 x128 46.6024 47.8984
150 x150 49.3358 49.0207
200 x200 49.1947 41.1604
220 x220 46.0073 37.5348
.png
100 x100 54.4270 50.8743
128 x128 50.9845 43.9930
150 x150 37.8703 42.2780
200 x200 42.5420 44.6707
220 x220 37.2588 36.2885
Baboon
.jpg
100 x100 49.7004 40.4878
128 x128 47.0068 41.3162
150 x150 43.8514 35.7607
200 x200 47.2930 35.1920
220 x220 48.1503 35.0314
.png
100 x100 47.1021 38.6549
128 x128 48.0422 37.6236
150 x150 45.1130 36.9323
200 x200 47.6768 38.3077
Experimental Results
15

16. CONCLUSION
Fragile watermarking scheme
Very good PSNR values > 35 dB
Watermarks can be successfully
embedded and extracted
16

17. REFERENCES
 N. Dey. P. Das ,”Session based Blind watermarking
technique with in NROI of ratinal Funds image for
Authentication Using DWT, spread spectrum
 A.K Pal, P.Das,N.dey “Odd-Even Embedding
Scheme based Modified Reversible Watermarking
Technique using Blueprint”
17

18. 18
THANK YOU