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Circular image plot (MATLAB)

by mikeph
Tags: circular, image, matlab, plot
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mikeph
#1
Jul27-11, 04:26 AM
P: 1,212
Hi,

Just came across this as an image in a book/monograph and it looks very MATLAB-esque, except I cannot figure out how to possibly create a circular image



Say I have a 500x500 matrix and want to plot it as a colour image in this way. Does anyone know how? I've been re-reading the same help files again and again with no progress.
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#2
Jul27-11, 08:41 PM
Sci Advisor
PF Gold
P: 1,469
transform the x and y coordinates to polar coordinates and plot the new coordinates,
plot3(cos(x), sin(y));
mikeph
#3
Jul29-11, 03:39 AM
P: 1,212
Thanks for the reply, I don't fully understand how to apply it to my problem (never been strong on plot tools), my image has no coordinates, it's just a 500x500 matrix. I don't need the axis, just for the plotter to not plot anything outside a circular region. Currently I'm using pcolor with "EdgeAlpha" to zero so it looks very similar to that image I linked, but it's a square.

mikeph
#4
Nov15-11, 06:35 AM
P: 1,212
Circular image plot (MATLAB)

Hi, just need to bump this, I still don't understand how to do this.
mikeph
#5
Apr26-12, 11:09 AM
P: 1,212
One more bump, I still can't find an answer, thanks

I really just need to know how to make the non-circle area white, at the moment I'm fiddling around with colour maps and manually changing the values to force it to look white, but it has side-effects.
mikeph
#6
Jun5-12, 05:42 AM
P: 1,212
Bumping to say I solved the problem.

The solution lies in the alpha data of the object.

For example you can use a ROI to make part of the object transparent, using

set(gco,'AlphaDataMapping','scaled','AlphaData',ROI)

Where ROI = 1 the image will stay opaque and where it is 0 the image will be transparent.


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