How to plot a circular Image?

I want to plot a binary image like this:

However, I only want the red region to be shown in the figure.How can I do this?

tnx in advance

[Geoff Hayes]

Ramin - what exactly are your inputs to draw the above? Do you determine the radius of the red circle? Do you decide on the number of solid black balls that fill the red region? Do you decide on the radius of each solid black ball?

Answer 1

[Image Analyst]

You can draw only the red circle by using rectangle().

For other approaches to drawing circles, see the FAQ on circles, or see my attached demos.

[ramin bba]

tnx a lot. All of them came in handy!

Answer 2

[Robert Cumming]

A couple of options for you:

% First create an axes and some data:

ax = axes;
ang=0:0.01:2*pi; 
xp=1*cos(ang);
yp=1*sin(ang);
patch ( xp, yp, 'w', 'parent', ax )
axis ( ax, 'equal' )

% option 1 - hide the axes to leave your image:

set ( ax, 'visible', 'off' )

% option 2 - set the background of your image to be the same as the parent:

set ( ax, 'color', get ( get ( ax, 'parent' ), 'color' ) )

[ramin bba]

thanks Robert. A question:

should I use the above after I have read my image? 'cause it is not working properly! it actually puts a disk on my current image and hides a circular portion of it! here is what I do:

a=imread('...');

imshow(a);

ax = axes;

ang=0:0.01:2*pi;

xp=1*cos(ang);

yp=1*sin(ang);

patch ( xp, yp, 'w', 'parent', ax )

axis ( ax, 'equal' )

set ( ax, 'color', get ( get ( ax, 'parent' ), 'color' ) )

[Robert Cumming]

My example draws a circle as an example. You would need to remove that part. You only need the last part which hides the axes, or changes the background colour.