In this present work, we propose a new reversible color image watermarking technique, using trigonometric functions. The proposed method embeds secret bits into the gray planes of color image, using interpolation method and few trigonometric functions. Experimental results presented in this paper shows that the watermark can be successfully embedded and extracted from an image, without distorting the original image using the proposed technique. The high Peak Signal to Noise Ratio (PSNR) values claims the robustness of the proposed method.
A. Embedding Watermark within an image
Step 1. Original image is read and divided into multiple 2×2 blocks.
Step 2. Each 2×2 block is converted into 3×3 blocks using interpolation.
Step 3. The values of newly inserted elements are changed using trigonometric functions.
Step 4. Logarithmic values of these new elements are taken and stored in a variable.
Step 5. Bit stream is chosen according to log values.
Step 6. The decimal values of those bit streams are embedded in the new elements of 3×3 blocks.
B. Extraction of Watermark from watermarked image
Step 1. Watermarked image 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.
Explanation of the proposed method
Our algorithm proposes a method to embed watermark within an image, using a simple interpolation technique. For example, I is the original image and C is the interpolated image (Cover image). Each 2 x 2 block in original image (I) is converted into 3 x 3 using the following formals,
C (1, 1) = I (1, 1);
C (1, 3) = I (1, 2);
C (3, 1) = I (2, 1);
C (3, 3) = I (2, 2);
Afterwards, those newly inserted elements are changed using trigonometric functions. In this current work, the following formals are used,
Similarly,
Similarly do c( 2,2),c(2,3),c(3,2). After changing the values, the updated image is C’. After that we will insert the each bit in the watermarked image(the small image that will be encrypted into the large host image,which is hidden into the host image ) into 3 x 6 block in the host image(large image,this image is common people seen) as in the interpolated new positions. The whole process will be described in the below image.
By this method next 4 bit in the 8 bit of the watermarking image bit is added in the next 3 x 3 block in the host image by this all the bit in the watermark is added into the host image. Now the new image C’’ is the watermarked image.
To extract the watermark from the image, first we have to recover the C’ image from the C’’ image using the same procedure as mentioned above.
Then we can obtain the bit in the watermark image by subtracting the bit value in the C’’ image by C’ image. And then collect the bit as by the inserting order and by using that image bit create the image and this is the recovered image.
THE PSNR VALUES ARE GET AROUND( 64.somthing)