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Re: How to find the pixel position [message #70755 is a reply to message #70672]

Thu, 29 April 2010 23:30

sid
Messages: 50
Registered: January 1995

Member

On Apr 30, 12:46 am, Aram Panasenco <panasencoa...@gmail.com> wrote:
> sid wrote:
>> On Apr 27, 11:24 am, Aram Panasenco<panasencoa...@gmail.com> wrote:
>>> sid wrote:
>>>> Hi,
>>>> My data is in fits format. The is of 1024 * 1024 array. The counts
>>>> vary from 5000 to 6000 and I know that 5500 counts is there in my
>>>> data, but I need to know at which pixel this 5500 counts occur
>>>> exactly, without displaying the image, because I need to do this for
>>>> several files. So each time I can't display and check for the pixel
>>>> position. please helpout in this regard.
>>>> regards
>>>> sid
>
>>> I think what you are saying (correct me if I am wrong) is that you have
>>> a 1024x1024 array, and you want to find where the pixel values are equal
>>> to 5500.
>
>>> You can use the WHERE function:
>
>>> fitsData = readfits('filename.fits')
>>> countValue = 5500
>
>>> findIndices = where(fitsData eq countValue)
>
>>> Note that the WHERE function returns one-dimensional subscripts. You can
>>> convert them back to two-dimensional subscripts (if you need to) using
>>> the ARRAY_INDICES function:
>
>>> rectIndices = array_indices([1024,1024],findIndices,/dimensions)
>
>>> Cheers
>>> ~Aram Panasenco
>
>> Hi,
>> I did like this
>> raw=readfits('filename.fits')
>> b=where(raw eq 2832.90)
>> I know that it occurs at raw(5,5)
>> so now if I do
>> print,b
>> it should print 5, since where function returns one dimensional
>> subscripts.(am I right, correct me if it is wrong)
>> but instead it is printing -1. Please help me out.
>> regards
>> sid
>
> Hey sid, other people have explained what your problem is already (can't
> compare float-point values in IDL). If you want to read a more detailed
> discussion on the subject, check out this article by David Fanning:
>
> http://www.dfanning.com/code_tips/comparearray.html
>
> ~Aram Panasenco

Thanks a lot for everybody's help and suggestions.
regards
sid

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[Message index]

		How to find the pixel position By: sid on Mon, 26 April 2010 22:16
		Re: How to find the pixel position By: Aram Panasenco on Thu, 29 April 2010 12:46
		Re: How to find the pixel position By: sid on Thu, 29 April 2010 23:30
		Re: How to find the pixel position By: Aram Panasenco on Thu, 29 April 2010 11:42
		Re: How to find the pixel position By: jeanh on Thu, 29 April 2010 08:18
		Re: How to find the pixel position By: d.poreh on Thu, 29 April 2010 03:22
		Re: How to find the pixel position By: Timm Weitkamp on Thu, 29 April 2010 02:49
		Re: How to find the pixel position By: sid on Thu, 29 April 2010 01:50
		Re: How to find the pixel position By: d.poreh on Thu, 29 April 2010 00:06

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