| Re: Creating a new image from an image input in IDL [message #70802 is a reply to message #70798] |
Wed, 05 May 2010 05:01   |
Jeremy Bailin
Messages: 618
Registered: April 2008
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Senior Member |
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On May 5, 2:45 am, bcubeb3 <barry.brian.barr...@gmail.com> wrote:
> After typing this line of code:
> IMAGE=READ_TIFF(FILEPATH('/bin/butterfly.tiff'))
> help, IMAGE
>
> I get the output
> IMAGE BYTE = Array[3, 4800, 6000]
>
> Now I want to write a computer program to systematically loop through
> each of the n x n pixels of the image and to use a coordinate system
> in pixel units to compute new coordinates based on the formula theta_s
> = theta - (size parameter of your choosing in units of
> pixels)*theta_hat.
>
> The vector theta_s tells me where to look in the original image to
> extract intensity information which will then store in my image array.
> I will use a bilinear scheme when assigning new intensity values that
> will be stored for my newly created image array theta. Now I have no
> idea how to even begin. I was looking for stuff online and I was
> looking at help manuals but all efforts proved futile. Let me know of
> your suggestions and I greatly appreciate your help on this.
>
> -Barry
So I think what you're saying (please correct me if I've
misunderstood!) is that you have a simple transformation between the
pixel coordinates of the new image and the pixel coordinates of the
old image. So there's two steps here:
1) Calculate the transformation for each of the pixel locations of the
new image
2) Copy the image values over
For 1) I would do something like this:
; size of image:
imagesize = size(image,/dimen)
nchan=imagesize[0]
nx=imagesize[1]
ny=imagesize[2]
npix = nx*ny
; get a 2D list of all pixel coordinates. This is going to take a LOT
of memory
; for a 4800x6000 image!
newcoords_2d = array_indices([nx,ny], lindgen(npix), /dimen)
; apply the transformation. I don't really understand your formula,
; but hopefully this example will help you.
; reform is needed to flatten it instead of being 1xNPIX
; X coordinate in old image, as a linear combination of X and Y
; coordinates of new image (oldX = A*newX + B*newY)
oldcoordsX = reform( A * newcoords[0,*] + B * newcoords[1,*], npix)
; Y coordinates in new image, as a linear combination of X and Y
; coordinates of new image (oldY = C*newX + D*newY)
oldcoordsY = reform( C * newcoords[0,*] + D * newcoords[1,*], npix)
Once you've done that, copying it over is easy (though again, very
memory-intensive):
newimage = bytarr(imagesize)
for chan=0,2 do newimage[chan,*,*] = oldimage[replicate(chan,npix),
oldcoordsX, oldcoordsY]
(NOTE: COMPLETELY UNTESTED)
-Jeremy.
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