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Re: blurry ellipse

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92375] Re: blurry ellipse
  • From: "Solomon, Joshua" <J.A.Solomon at city.ac.uk>
  • Date: Tue, 30 Sep 2008 07:33:07 -0400 (EDT)
  • References: <gat9g4$ec5$1@smc.vnet.net> <gavqku$emm$1@smc.vnet.net> <gbajun$ff$1@smc.vnet.net> <gbjm2t$375$1@smc.vnet.net>

correct. thanks.
j

On 26/09/2008 23:01, in article gbjm2t$375$1 at smc.vnet.net, "dh"
<dh at metrohm.ch> wrote:

> 
> 
> Hi Solomon,
> 
> I think this is an artefact of the original coarse grained picture. The
> 
> convolution treats every block (square) of pixels equally. But look at
> 
> the original picture. If you imagine some small square, you will see
> 
> that there are more or less white pixels inside the square, depending on
> 
> where the squre is placed. This differences will persits, because the
> 
> convolution will simply smear the "total white" on a larger surface.
> 
> To improve, we therefore need a more fine grained original.
> 
> Daniel
> 
> 
> 
> Solomon, Joshua wrote:
> 
>> thanks. but notice, intensity also varies as you go around your ellipse.
> 
>> j
> 
>> 
> 
>>  On 19/09/2008 10:16, in article gavqku$emm$1 at smc.vnet.net, "dh"
> 
>> <dh at metrohm.ch> wrote:
> 
>> 
> 
>>> n=100;
> 
>>> 
> 
>>> pict=Table[0,{n},{n}];
> 
>>> 
> 
>>> Scan[(pict[[Round[n/2+n/5  Sin[#]],Round[n/2+2
> 
>>> 
> 
>>> n/5Cos[#]]]]=1)&,Range[0,2Pi,0.01]];
> 
>>> 
> 
>>> Graphics[Raster[pict]]
> 
>>> 
> 
>>> kernel={{1,1},{1,1}}; pict=ListConvolve[kernel,pict];pict=pict/Max[pict];
> 
>>> 
> 
>>> Graphics[Raster[pict]]
> 
>>> 
> 
>>> kernel={{1,1,1},{1,1,1},{1,1,1}};
> 
>>> 
> 
>>> pict=ListConvolve[kernel,pict];pict=pict/Max[pict];
> 
>>> 
> 
>>> Graphics[Raster[pict]]
> 
>>> 
> 
>>> kernel={{1,1,1,1},{1,1,1,1},{1,1,1,1},{1,1,1,1}};
> 
>>> 
> 
>>> pict=ListConvolve[kernel,pict];pict=pict/Max[pict];
> 
>>> 
> 
>>> Graphics[Raster[pict]]
> 
>> 
> 
>> 
> 
> 
> 
> 



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