I am working on a watermarking project using dwt and dct . The embedding seems to be correct, but after the embedding using alpha equation, the resulted watermarked image has a mix of negative and positive values, when I converted to uint8 the watermark can not be extracted. If I save it as double image (tif format),the watermark is extracted correctly, But if I attacked the double image , the watermark is lost completely because matlab convert it in the range[0,1],
What is the correct way to save and manipulate watermarked image to extract the watermark with any data loss(without attack) and how to extract it with attacks?
plz help me I do not have any time more
thanks
instead of letting matlab convert it to [0,1] range, you can do it yourself before saving as uint8, and store the transformation in the image header.
the operation will be (im-min(min(im))/)(max(max(im))-min(min(im))
before this operation, store the im_max and im_min values, and add this to the image header (or filename), so u can use this to scale the uint8 image back (reverse operation as above) when u need to extract the watermark
Thanks sir but I have tried the scaling , but it does not work :)
any help
Thank you Mrs.Murthy ,, But I do not understand how to convert watermark image in another set
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