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prove stegano existance with PSNR/MSB
Posted: 2012-12-18T00:07:36-07:00
by nunjimmimya
hi
as the title it implies
i would like to know how to compare original image and stegano image with PSNR or MSB effectively
it is because i tried to compare original image and stegano image with PSNR and the result is awkward
as far a i understand, PSNR value ranging from 0 - 100 and stegano image is consider readable if PSNR value is above 30
but my value is 110
attach is result code from command line
Code: Select all
compare -verbose -metric PSNR Desktop/kami.png Desktop/stegano.png Desktop/kami_dif.png
Desktop/kami.png PNG 640x480 640x480+0+0 8-bit sRGB 348KB 0.030u 0:00.019
Desktop/stegano.png PNG 640x480 640x480+0+0 16-bit sRGB 454KB 0.040u 0:00.049
Image: Desktop/kami.png
Channel distortion: PSNR
red: 110.865
green: 110.922
blue: 110.916
all: 110.901
appreciate your help
thank you
Re: prove stegano existance with PSNR/MSB
Posted: 2012-12-18T11:37:41-07:00
by fmw42
PSNR is expressed as decibels and so can in principle be larger than 100. But even 100 is a huge difference
see
http://www.imagemagick.org/Usage/compare/#statistics
You might be better using rmse (root mean squared error).
If I do
compare -metric psnr rose: rose_message.png null:
104.287
my guess is that is really -104.287 (amplitude not power) decibels as there should be very little difference
compare -metric rmse rose: rose_message.png null:
0.400052 (6.1044e-06)
The 6.1e-06 is a difference in the range of 0 to 1. So this is 0.0006 % error
see
http://en.wikipedia.org/wiki/Decibel
I suspect the only issue is that it should be negative, which I would suspect is an oversight.
Re: prove stegano existance with PSNR/MSB
Posted: 2012-12-19T22:14:04-07:00
by nunjimmimya
requirement for my project is whether use PSNR or MSB(Most Significant Bit)
if i not wrong, the script will generate MSB (correct me if I'm wrong) when 2 image are being compared
i think i will go for MSB
thank you for your time
fmw42 wrote:PSNR is expressed as decibels and so can in principle be larger than 100. But even 100 is a huge difference
see
http://www.imagemagick.org/Usage/compare/#statistics
You might be better using rmse (root mean squared error).
If I do
compare -metric psnr rose: rose_message.png null:
104.287
my guess is that is really -104.287 (amplitude not power) decibels as there should be very little difference
compare -metric rmse rose: rose_message.png null:
0.400052 (6.1044e-06)
The 6.1e-06 is a difference in the range of 0 to 1. So this is 0.0006 % error
see
http://en.wikipedia.org/wiki/Decibel
I suspect the only issue is that it should be negative, which I would suspect is an oversight.
Re: prove stegano existance with PSNR/MSB
Posted: 2012-12-19T22:21:56-07:00
by fmw42
I do not believe that there is a MSB error measure, only
MAE ..... Mean absolute error (average channel error distance)
MSE ..... Mean squared error (averaged squared error distance)
RMSE .... (sq)root mean squared error -- IE: sqrt(MSE)
or
PAE ..... Peak Absolute Error (within a channel, for 3D color space)
PSNR .... Peak Signal to noise ratio (used in image compression papers)
see error measures at
http://www.imagemagick.org/Usage/compare/#statistics