| creating elliptically shaped images [message #37099] |
Mon, 24 November 2003 07:12  |
mruschin
Messages: 3
Registered: November 2003
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Junior Member |
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I'd like to form an image which has an elliptical shape and where all
the pixels within this ellipse have values corresponding to any given
function that I would specify, the simplest example being a uniform
image (i.e. a value of 1 for all the pixels in the ellipse). Is there
any nice way to do this in IDL or MATLAB other than looping through
all the pixels and determining whether any given one lies within the
ellipse?
Mark
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| Re: creating elliptically shaped images [message #37175 is a reply to message #37099] |
Wed, 03 December 2003 15:03  |
Paul Sorenson
Messages: 48
Registered: May 2002
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Member |
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mruschin@hotmail.com (mark) wrote in message
news:<a9116224.0311240712.618f4088@posting.google.com>...
>> I'd like to form an image which has an elliptical shape and where all
>> the pixels within this ellipse have values corresponding to any given
>> function that I would specify, the simplest example being a uniform
>> image (i.e. a value of 1 for all the pixels in the ellipse). Is there
>> any nice way to do this in IDL or MATLAB other than looping through
>> all the pixels and determining whether any given one lies within the
>> ellipse?
>
This sounds like a job for IDLanROI::ContainsPoints. It can identify what
points are in a region without requiring a loop.
-Paul Sorenson
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| Re: creating elliptically shaped images [message #37182 is a reply to message #37099] |
Wed, 03 December 2003 09:24 |
condor
Messages: 35
Registered: January 2002
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Member |
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mruschin@hotmail.com (mark) wrote in message news:<a9116224.0311240712.618f4088@posting.google.com>...
> I'd like to form an image which has an elliptical shape and where all
> the pixels within this ellipse have values corresponding to any given
> function that I would specify, the simplest example being a uniform
> image (i.e. a value of 1 for all the pixels in the ellipse). Is there
> any nice way to do this in IDL or MATLAB other than looping through
> all the pixels and determining whether any given one lies within the
> ellipse?
In IDL at least, you can send raw strings to your output device.
Depending on the device, you could use that to send clipping
instructions.
If you were plotting into a PostScript file for example, this might
look vaguely like this:
;; Some random dots to plot:
x=randomu(seed,5000)
y=randomu(seed,5000)
set_plot,'PS'
device,/landscape
;; plot without clipping to show where the dots are:
plot,x,y,psym=3
;; PS clipping path -- here vaguely elliptical, but could be anything:
clipstring='currentpoint 37 rotate 1 .5 scale '+$
'newpath 15000 5000 5000 0 360 arc clip '+$
'1 2 scale -37 rotate newpath moveto'
device,output=clipstring
;; plot again with different psym to illustrate clipping:
oplot,x,y,psym=4
device,/close
set_plot,'X'
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