Re: Rep:[WM]: Benchmark

[phil <ipebrown@yahoo.com.br>]

Tpj,
I test all PSNR of the images I get. But the way StirMark 4 generates the  images (image_PSNR_0, image_PSNR_10, image_PSNR_20,
...., image_PSNR_100)  does not make sense to me...


At 09:08 AM 3/18/2005, you wrote:
>Felipe,
>    I don't know what do you say about Stirmark 4.0, but as far as I
>know the PSNR ("Peak Signal Noise Ratio") is a test, not an attack, to
>evaluate the degree of noise inserted into a image at pixel level. More
>exactly, it evaluates the Cr,Cb (chrominance) and Y (luminance)
>components. If you are working with grayscale images, it will give Y
>value (dB units).
>    I have written and experimented that if a watermark is inserted
>into a image, the Y PSNR will be probably about 40-45dB.  I recommend
>you that search about PSNR into the net.
>
>    If you work in linux, there are commands with you can simulate this
>test:
>    bmptoppm : to convert a .bmp image to .ppm format. Perhaps exists a
>pgmtoppm command, try it.
>
>    pnmpsnr image_orig image_marked : to apply the PSNR test.
>
>
>I hope this help you.
>tpj.
>
>
>
>
>
>-----Message d'origine-----
>De: Phil <felipe@lps.ufrj.br>
>A: <watermarking@watermarkingworld.org>
>Date: 17/03/05
>Objet: [WM]: Benchmark
>
>I need some help with stirmark 4. My marking system uses grayscale
>images (.pgm). I transformed to .ppm, then put the images at set1
>directory.
>Then StirMark created some images called image_PSNR_0, image_PSNR_10,
>..., image_PSNR_100. What is the meaning of this atack PSNR ?
>Is it an atack ?
>Thanks for the atention.
>
>  Felipe Aquino.
>
>  +++++++++++++++++++++++++++++++++++++++++++++
>          ___             _
>          |_ _ |. _  _   |_| _    .._  _
>          | (/_|||_)(/_  | |(_|(_||| |(_)
>                 |            |
>
>  felipe@lps.ufrj.br
>  LPS  - Laboratorio de Processamento de Sinais  UFRJ - Universidade
>Federal do Rio de Janeiro  Rio de Janeiro, Brasil.
>  +++++++++++++++++++++++++++++++++++++++++++++


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