Scaling factor in two matrix
Scaling factor in two matrix
Hello,
I reading an article and i can't understand well about scaling factor.
Could you give me definition and example about scaling factor?
How can embed one matrix to other matrix with scaling factor?
Thanks
I reading an article and i can't understand well about scaling factor.
Could you give me definition and example about scaling factor?
How can embed one matrix to other matrix with scaling factor?
Thanks
 fmw42
 Posts: 23615
 Joined: 20070702T17:14:5107:00
 Authentication code: 1152
 Location: Sunnyvale, California, USA
Re: Scaling factor in two matrix
It might help if you give a reference to that article.
Guess at this point is the the diagonal elements of the D matrix used for the watermarking are scaled (magnified) to enhance the separability of low diagaonal values where the image is flat colored.
Guess at this point is the the diagonal elements of the D matrix used for the watermarking are scaled (magnified) to enhance the separability of low diagaonal values where the image is flat colored.
Re: Scaling factor in two matrix
Sure,
Reference article is here and we can read it free.
http://www.sciencedirect.com/science/ar ... 0915001945
Reference article is here and we can read it free.
http://www.sciencedirect.com/science/ar ... 0915001945
Re: Scaling factor in two matrix
Emailed to the owner article and answered me, now could you give me more explain about it?
Embedding a matrix into another one can do as matrix addition. Scaling factor is used for obtaining the invisibleness of the watermark. Pls find the below.
Watermarked= A + (s*B).
Here A &B are matrices of cover and watermark. s is the scaling factor. U may vary this according to invisibleness that ur need.
Embedding a matrix into another one can do as matrix addition. Scaling factor is used for obtaining the invisibleness of the watermark. Pls find the below.
Watermarked= A + (s*B).
Here A &B are matrices of cover and watermark. s is the scaling factor. U may vary this according to invisibleness that ur need.

 Posts: 10489
 Joined: 20100123T23:01:3307:00
 Authentication code: 1151
 Location: England, UK
Re: Scaling factor in two matrix
An image is an array of pixels. It is also a number of arrays of values, where each array represents one channel.
Image arrays can be added together. We can multiply one array by a scalar factor (that is, a single value, like 0.05) before adding it to another.
In IM, "compose Mathematics" is useful for this.
Image arrays can be added together. We can multiply one array by a scalar factor (that is, a single value, like 0.05) before adding it to another.
In IM, "compose Mathematics" is useful for this.
snibgo's IM pages: im.snibgo.com
Re: Scaling factor in two matrix
We have the below formula
Watermarked= A + (s*B).
If A and B between 0 and 255, for example we have:
S = 0.5 , A = 250 and B = 245
Watermarked = 250 + (0.5*245) = 372.5 !!!
But each pixel is 8bit and should be between 0 <= intensity <= 255 .
Watermarked= A + (s*B).
If A and B between 0 and 255, for example we have:
S = 0.5 , A = 250 and B = 245
Watermarked = 250 + (0.5*245) = 372.5 !!!
But each pixel is 8bit and should be between 0 <= intensity <= 255 .

 Posts: 10489
 Joined: 20100123T23:01:3307:00
 Authentication code: 1151
 Location: England, UK
Re: Scaling factor in two matrix
Well, not exactly. A and B are arrays. So each value in array B is multiplied by s, then added to the corresponding value in B.
Yes, the simple formulae can give overflow (aka clipping). So the array values can be reduced first, or the result is reduced after the calculation, or a different formula used:
out = A*(1s) + B*s
This is a blending function.
Yes, the simple formulae can give overflow (aka clipping). So the array values can be reduced first, or the result is reduced after the calculation, or a different formula used:
out = A*(1s) + B*s
This is a blending function.
snibgo's IM pages: im.snibgo.com
Re: Scaling factor in two matrix
Thank you for your reply,
The below formula is your formula? or it's from other papers?
out = A*(1s) + B*s
We have out intensity and watermark is fine.
Now with Scale(for example : 0.5 ) and out ,how we can extract A and B ?
The below formula is your formula? or it's from other papers?
out = A*(1s) + B*s
We have out intensity and watermark is fine.
Now with Scale(for example : 0.5 ) and out ,how we can extract A and B ?

 Posts: 10489
 Joined: 20100123T23:01:3307:00
 Authentication code: 1151
 Location: England, UK
Re: Scaling factor in two matrix
It's a standard blending function. If you know three of the four variables (out, A, B, s) you can easily calculate the fourth, for example:
A = (out  B*s) / (1s)
A = (out  B*s) / (1s)
snibgo's IM pages: im.snibgo.com
Re: Scaling factor in two matrix
Thank you for your reply,snibgo wrote:It's a standard blending function. If you know three of the four variables (out, A, B, s) you can easily calculate the fourth, for example:
A = (out  B*s) / (1s)
yes, but when watermark image in the cover image(A and B) , we lost A and B in watermark image.
We just s and out . we don't have A or B.
We don't have B to calculate A. or A to calculate B.We just s and out

 Posts: 10489
 Joined: 20100123T23:01:3307:00
 Authentication code: 1151
 Location: England, UK
Re: Scaling factor in two matrix
The paper is vague on that. It also says it is "embedded on the singular values of cover image", but there are only 2*min(W+H) nonzero values in the "singular values" matrix. So I don't know how that works.
snibgo's IM pages: im.snibgo.com