matlab DWT digital watermarking program

First of all, I don't know if you know how to use Matlab. if, you do, there should be a simple DWT watermark embedding program.

Reading the image, DWT transforms are needless to say, right?

One thing I don't quite understand is, when is the preprocessing done? After doing it on the original image, after doing the DWT transform embedded?

Then the string has as much information as the original image. The watermark effect would be 。。。。。。

If you want to embed it, you have to do the same DWT transform as the original image. Otherwise, there is too much embedded information. If you do that, it's the same as the latter embedding method.

That is, do the DWT transform first, assuming that the four images after the final DWT transform are A,B,C,D.

The A image doesn't move, B and C can be embedded, and the D image compression is gone. So, the A image do histogram processing, and then embedded with the watermark to, B and C images.

You ask inside, histogram compression to [N, 255-N]. n=G/2;?

The histogram gray scale range [N, 255-N], we set ? :

Oimg=A image;

WMKimg=Watermark;

Zimg=Histogram adjusted image;%%? That is, the color number range is [?N,?255-N]?

That is, a picture of [0,255] is now going to be displayed with a grayness of [N,255]. (This histogram variation is straightforward to make)

After analyzing this, it's easier.

Wimg=Oimg and Zimg difference matrix.

Then, Wimg and WMKimg are processed according to the random key, and embedding is done

The top one is the A diagram.