[WM]: Rotational normalization

["Mostafa mohsen" <orange1704@hotmail.com>]

Hi all
           I am trying to design an algorithm to calculate the rotational 
angle of the watermarked image with x-axis and rotate it back to the 
horizontal as for image normalization before watermarking detection but the 
problem is that the pixel values change greatly when image first rotate with 
theta then -theta!!!!

I was expecting that the pixel values remain the same after removing the 
dark frame resulted from rotation but unfortunately the pixel values change.

i.e

IM=imrotate(IO,45);
IM=imrotate(IO,-45);

where 45 is the angle of the image with respect of the x-axis

but after removing the dark frame IM not equal IO !!!!

Any advice ??!!

Your quick response is highly appreciated.

Thanks and best regards

Mostafa!


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