Image extraction from Watermarked image

Hello everyone...

I am trying to extract "watermark image" from a watermarked image. For this i am selecting original image of 512x512 and watermark image of size 64x64. then i am normalizing the original image, applying DCT & converting into 8x8 Blocks. for applying dct i am using

             T = dctmtx(8);
             dct = @(block_struct) T * block_struct.data * T';
             D1 = blockproc(norm00,[8 8],dct);

After that i am taking "watermarked image". again i am doing same process as mentioned above. after that as i embedded watermark only in 512 [since i am converting original image as well as watermark image into 8x8 block,so 64x8 = 512] blocks in "watermarked image".

so i am subtracting [{ first 512 blocks of watermarked image - first 512 blocks of original image } divided by embedding coefficient] for extracting the "watermark image".

but i am not getting the proper image, i am getting Black image with some irregular white rectangular blocks. code is not showing any error. so can any one suggest what are the modification required me for the getting the Watermark image. plz help me to come out from this problem. i need it urgently.thanks in advance......

[amitesh kumar]

there is no one who having idea about watermark extraction...........!!!!! plz help me

[Andreas Goser]

I strongly believe many exclamation marks do not bring you forward here, but a clearer description. Especially in image processing, providing images is a real help.

[kishore rajkumar]

how to extract watermark from original image in mat lab

Answer 1

[kishore rajkumar]

    T = dctmtx(8);
             dct = @(block_struct) T * block_struct.data * T';
             D1 = blockproc(norm00,[8 8],dct);