Re: blurry ellipse

• To: mathgroup at smc.vnet.net
• Subject: [mg92253] Re: blurry ellipse
• From: dh <dh at metrohm.ch>
• Date: Wed, 24 Sep 2008 03:32:42 -0400 (EDT)
• References: <gat9g4\$ec5\$1@smc.vnet.net> <gavqku\$emm\$1@smc.vnet.net> <gbajun\$ff\$1@smc.vnet.net>

```
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]]

>

>

--

Daniel Huber

Metrohm Ltd.

Oberdorfstr. 68

CH-9100 Herisau

Tel. +41 71 353 8585, Fax +41 71 353 8907

E-Mail:<mailto:dh at metrohm.com>

Internet:<http://www.metrohm.com>

```

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