How to split image based on sectors.

I have an image that I need to segment.

The segments will be something like the above image. I may need to vary the number segments based on the angle. (Here I have taken roughly 22.5 degrees for each segment. I figured that I would generate multiple masks like the one shown below (with the tips touching of course) for each sector.

But I am not sure how to go about.

I am trying to do this to analyze the content in each of these sectors and I would be required to change the angles for each image.

Any help in this direction will be greatly appreciated. Thanks in advance.

Answer 1

[Guillaume]

Here is one way of doing it:

%width: width of mask images to generate, in pixels
%height: height of mask images to generate, in pixels
%anglestep: angle of segments, in degrees
width = 256; height = 256;
anglestep = 22.5;

[y, x] = ndgrid((1:height) - floor(height/2), (1:width) - floor(width/2)); %cartesian coordinates of each pixel
pixelangle = mod(atan2d(y, x), 180); %convert to angle in range [0, 180]
segment = discretize(pixelangle, 0:anglestep:180);  %discretize into segment number
masks = arrayfun(@(sid) segment == sid, 1:ceil(180/anglestep), 'UniformOutput', false); %convert to masks

%display masks
for m = 1:numel(masks) 
   figure; imshow(masks{m}); title(sprintf('mask %d', m));  
end

[SHISHIR PARAMATHMA RAO]

This is very nice way of doing it. But the only drawback is in all the masks, the tips are not touching. But I'm sure I can handle that. Thanks.