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Re: Working with 2 partially overlapping images of different array sizes [message #28865 is a reply to message #28836]

Fri, 11 January 2002 19:08

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

aqueous0123@yahoo.com (aqueous) writes:
> Sorry, I'm new to this image processing stuff.
>
> I have 2 images of different sizes and different, but overlapping,
> locations on the globe. E.g., 2 satellite images from different
> sensors.
>
>
> |||||||||||||||| <- IMAGE_1 = bytarr(532,532)
> | |
> | ''''''''''''''''''
> | ' | '
> | ' | '
> | ' | '
> | ' | '
> | ' | '
> ||'||||||||||||| ' <- IMAGE_2 = bytarr(250,200)
> ''''''''''''''''''
>
... [ deletions ] ...
> What I wish to do is create a new array IMAGE_3 that is the same array
> size (532,532) as IMAGE_1 AND also has the same physical location as
> IMAGE_1, but with IMAGE_2's data where IMAGE_1 and IMAGE_2 overlap
> (the 2's in the graphic below). Where they do not overlap, I'll just
> fill IMAGE_3 with nearest neighbor of IMAGE_2 (the 0's in the grahic
> below).
>
... [ deletions ] ...

What you are asking for is 100% what the function INTERPOLATE() will
do for you. The only trick is to make the X and Y arrays for the
interpolation. You are trying to interpolate IMAGE2 onto the grid for
IMAGE1, so what you want is an array of X values and Y values that
express the IMAGE1 grid in the coordinate system of IMAGE2.

;; Length of image 2 in the X and Y directions
lenx2 = max(lons2)-min(lons2) & leny2 = max(lats2)-min(lats2)
;; Pixel sizes of each image
dx2 = lenx2/n_elements(lons2) & dy2 = leny2/n_elements(lats2)

x1 = (lons1-lons2(0))/dx2
y1 = (lats1-lats2(0))/dy2

image3 = interpolate(image2, x1, y1, /grid)

Based on what you said, you definitely don't want to use MISSING,
because you want nearest neighbor on the outskirts where IMAGE2 is not
defined. [ If you really wanted to set to zero then you would say,
MISSING=0. ]

Good luck,
Craig

--
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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		Re: Working with 2 partially overlapping images of different array sizes By: Craig Markwardt on Tue, 15 January 2002 12:19
		Re: Working with 2 partially overlapping images of different array sizes By: aqueous0123 on Tue, 15 January 2002 11:19
		Re: Working with 2 partially overlapping images of different array sizes By: Craig Markwardt on Fri, 11 January 2002 19:08
		Re: Working with 2 partially overlapping images of different array sizes By: Pavel A. Romashkin on Fri, 11 January 2002 14:04
		Re: Working with 2 partially overlapping images of different array sizes By: David Fanning on Fri, 11 January 2002 12:44
		Re: Working with 2 partially overlapping images of different array sizes By: aqueous0123 on Thu, 17 January 2002 14:46

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