Re: Improving the quality of a blocky image

On Jun 9, 5:36 pm, Martin Brown <|||newspam...@[EMAIL PROTECTED]
>
wrote:
> AJ wrote:
> > Hi All,
>
> > I have an image which is very blocky (image can be seen at
> >http://img222.imageshack.us/my.php?image=degradedimagesh2.png)
and
> > would like to try and improve it's quality as much as possible.
>
> > I understand that the image is of such a poor quality that I do not
> > expect any huge improvements - that is not my aim, my aim is to see if
> > it can be improved at all, and if so, which method(s) could yield the
> > best results.
>
> > So far I have tried some iterative restoration techniques such as
> > Richardson-Lucy deconvolution and Blind deconvolution - both have
> > proved to give a slight improvement.
>
> > I was hoping someone would have some other suggestions as to how I
> > could possibly improve the image.
>
> You could play the match boundary continuity game with a cosmetic
> enhancement. I think the IJG codec can be persuaded to do this with
> suitable options.
>
>
>
> > Just in case understanding how the image was degraded in the first
> > place might help lead to a good suggestion for improvement algorithms,
> > I created the image using the following steps:
>
> > * 8x8 Sub-Block and DCT image
> > * store top 2 coefficients from each sub-block
> > * use these to create a new image
>
> So your reconstruction is from DC and lowest frequency horizontal
> component only? I don't think you can do much starting from there.
>
> Taking a subset square of low frequency coefficients around the DC
> component would give you a classic undersampling problem. eg 2x2 or 3x3
> measured components. But unless the reconstructed image clips against 0
> or 255 you don't get much by way of clues to regain resolution lost by
> the downsampling. And your test image is well clear of either.
>
> A simple field of white dots on a pure black ground would give you a
> test image where you might stand a better chance of success.
>
> In an ideal world maxent or another optimised nonlinear reconstruction
> might hope to extrapolate resolution to 3x the highest measured
> frequency for regions with the best signal to noise.
>
> Regards,
> Martin Brown
> ** Posted fromhttp://www.teranews.com**

Thanks for the reply.

Could you elaborate on the "match boundary continuity game" for the
IJG codec.  I had a search but couldn't find any useful information.

Many thanks