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Re: How to find the pixel position [message #70688 is a reply to message #70640]

Thu, 29 April 2010 03:22

d.poreh
Messages: 406
Registered: October 2007

Senior Member

On Apr 29, 2:49 am, Timm Weitkamp <weitk...@esrf.fr> wrote:
> On Apr 29, 10:50 am, sid <gunvicsi...@gmail.com> wrote:
>
>
>
>
>
>> On Apr 29, 12:06 pm, Dave Poreh <d.po...@gmail.com> wrote:
>
>>> On Apr 28, 11:40 pm, sid <gunvicsi...@gmail.com> 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
>
>>> Look at the data type: float double integer?
>
>> data type is float
>
> Trying to find "equality" between two float expressions is like trying
> to put a pencil upright on its tip and hoping that it will not fall
> over. It will hardly ever work. One solution could be to replace the
> line "b=where(...)" in your code by
>
> myval = 2832.90
> epsilon = .05
> b = where(ABS(raw-myval) LE epsilon)
>
> Timm

Or fix(myval*100) then search for data with where(...)

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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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