| create oval shape [message #91737] |
Tue, 18 August 2015 09:41  |
g.nacarts
Messages: 148
Registered: November 2013
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Senior Member |
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Hi
I want to create two oval shapes where the enclosed pixels have fixed values. I tried the following but are rectangles, as expected of course.
Im = fltarr(300,300)
A[19:68,40:115] = 2.
A[40:55,62:82] = 1.
Can anyone help with this? Instead of rectangles creating oval shapes with fixed values.
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| Re: create oval shape [message #91738 is a reply to message #91737] |
Tue, 18 August 2015 10:11  |
Jeremy Bailin
Messages: 618
Registered: April 2008
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Senior Member |
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On Tuesday, August 18, 2015 at 11:41:13 AM UTC-5, g.na...@gmail.com wrote:
> Hi
>
> I want to create two oval shapes where the enclosed pixels have fixed values. I tried the following but are rectangles, as expected of course.
>
> Im = fltarr(300,300)
>
> A[19:68,40:115] = 2.
> A[40:55,62:82] = 1.
>
> Can anyone help with this? Instead of rectangles creating oval shapes with fixed values.
I would use DIST_ELLIPSE from the idl astronomy library to get the distances from the center of the ellipse to each point in the image, and then use that distance to decide whether to set it or not.
I.e. to fill in an ellipse with an axis ratio of 2:1 centered at (x_center, y_center) with a semi-major axis length of length "radius":
dist_ellipse, ellipse_distances, [300,300], x_center, y_center, 2.0
A = ellipse_distances le radius
-Jeremy.
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| Re: create oval shape [message #91742 is a reply to message #91741] |
Tue, 18 August 2015 13:45 |
g.nacarts
Messages: 148
Registered: November 2013
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Senior Member |
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I didn't understand how to use the DIST_ELLIPSE though.
I typed
> IDL dist_ellipse, ellipse_distances, [300,300], x_center, y_center, 2.0
And I got the following:
Syntax - DIST_ELLIPSE, im, n, xc, yc, ratio, pos_ang, /DOUBLE
im - output elliptical mask image array
n - size of output image mask, scalar or 2 element vector
xc,yc - coordinates of ellipse center, scalars
ratio - ratio of major to minor axis of ellipse, scalar
pos_ang - position angle, counterclockwise from up
I didn't see how I'll get the distances from center using this function.
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| Re: create oval shape [message #91744 is a reply to message #91742] |
Tue, 18 August 2015 20:10 |
Jeremy Bailin
Messages: 618
Registered: April 2008
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Senior Member |
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On Tuesday, August 18, 2015 at 3:45:46 PM UTC-5, g.na...@gmail.com wrote:
> I didn't understand how to use the DIST_ELLIPSE though.
>
> I typed
>> IDL dist_ellipse, ellipse_distances, [300,300], x_center, y_center, 2.0
>
> And I got the following:
>
> Syntax - DIST_ELLIPSE, im, n, xc, yc, ratio, pos_ang, /DOUBLE
> im - output elliptical mask image array
> n - size of output image mask, scalar or 2 element vector
> xc,yc - coordinates of ellipse center, scalars
> ratio - ratio of major to minor axis of ellipse, scalar
> pos_ang - position angle, counterclockwise from up
>
> I didn't see how I'll get the distances from center using this function.
It looks like the pos_ang parameter is required (Wayne: the documentation says it is optional), so use 0 for that to align the axes of the ellipse with the x and y axes.
What you will get after running it is a 300x300 array where the value of each element is the semi-major axis of the ellipse that goes through that element and is centered at (x_center, y_center).
-Jeremy.
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