why after I use the imwrite function, the pixels in the image are changed diferrent? before I convert from double matrix to uint8 matrix ?

embed1=uint8(blkproc(embed1,[8 8],@idct2));

imwrite(embed1,'embeddct.jpg');

AA=imread('embeddct.jpg');

Answer 1

[Looky]

This is likely a result from the compression/decompression process involved when saving to a jpg file. Choose a better suited file format like '.bmp' if you want the exact equality of saved and loaded data.

imwrite(embed1,'embeddct.bmp');

AA=imread('embeddct.bmp');

Edit: Here is a better explanation of this problem and how to fix it.