On Jun 20, 4:22 pm, Thomas Richter <t...@[EMAIL PROTECTED]
> wrote:
> AJ schrieb:
>
> > Hi All,
>
> > I was hoping someone would be able to explain why something I have
> > noticed during some image processing analysis occurs.
>
> > When I am working with extremely degraded images, and am trying
> > different techniques to improve them, I often measure the PSNR (Peak
> > Signal-to-Noise Ratio) of the degraded image against the original,
> > undamaged image. Often, I find that the techniques that give the best
> > (highest) PSNR dB value are NOT the ones that give the best subjective
> > quality i.e. I chose restoration techniques that give a lower PSNR
> > because they LOOK better.
>
> > Can anyone explain why this happens?
>
> PSNR relates bad to human vision. You should try different metrics
> with a better correlation to subjective quality.
>
> Recommendations: MS-SSIM (Sheik & Bovik) works quite ok (though not
great),
> VDP (Daly's Visual Difference Predictor) works much better, though it is
> grey-scale only and it is extremely slow.
>
> > Maybe it is something to do with
> > the fact that the image quality of the degraded image is so poor to
> > start with, that using PSNR is not that helpful?
>
> If you want to measure subjective quality, PSNR is not very helpful to
begin with...
>
> So long,
> Thomas
Hi Thomas,
Many thanks for the reply.
I am using Matlab for my experimentation. Do you know if there is a
Matlab implementation of MS-SSIM (Sheik & Bovik) or VDP (Daly's Visual
Difference Predictor)?
I have had a google but no luck. I would like to avoid re-writing any
code if it is already available, to save time and effort!
Kind regards,
AJ
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