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Re: Calculate gradient [message #70082]

Sat, 13 March 2010 00:35

James[2]
Messages: 44
Registered: November 2009

Member

You could use the SOBEL operator. This convolves the image with
kernels like so:

-1 0 1 1 2 1
-2 0 2 0 0 0
-1 0 1 -1 -2 -1

to get approximations of the x and y gradient respectively. IDL's
built-in SOBEL routine returns the magnitude, i.e. the sum of the
absolute values of each of these convolutions. It would be simple to
make the kernels yourself and use CONVOL if you want to keep the x and
y gradients separate.

I don't know much about contour plotting in IDL, but the CONTOUR
function is probably a good place to start...

On Mar 12, 1:41 pm, mslarkin <enhlw...@gmail.com> wrote:
> Hi IDL experts,
> I have a 2-D array (2708x4060), containing reflectance data. Is it
> possible to calculate the reflectance gradient (i.e. the rate of
> reflectance change over distance or array grid) throughout the array,
> and then draw lines of equal gradient (note that they’re NOT contour
> lines)?
> Thank you very much for your help!
> IDL beginner

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[Message index]

		Re: Calculate gradient By: James[2] on Sat, 13 March 2010 00:35
		Re: Calculate gradient By: R.G.Stockwell on Fri, 12 March 2010 14:40
		Re: Calculate gradient By: pgrigis on Fri, 12 March 2010 14:37

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