Dividing the image into equal number of parts in Matlab

Question

I have lena image in Matlab. First I need to find the centroid C, and then divide the image into equal number of parts. I can calculate the centroid of the image but from that how can I divide the image into equal number of parts as shown below. Please anyone help me.

Thanks

Answer 1

Using poly2mask to create binary sectors and using the resulting sectors for indexing

Code:

im = imread('peppers.png');
r = 300;
out1 = ones(max(size(im,1),r*2)+2,max(size(im,2),r*2)+2,3).*255;

xoffset = floor((size(out1,2)-size(im,2))/2);
yoffset = floor((size(out1,1)-size(im,1))/2);

out1(yoffset:yoffset+size(im,1)-1,xoffset:xoffset+size(im,2)-1,:) = im(:,:,:);
im = out1;

cy = floor(size(im,1)/2);
cx = floor(size(im,2)/2);

figure;
imshow(uint8(im));
hold on
pos = [cx-r+1 cy-r+1 r*2 r*2];
rectangle('Position',pos,'Curvature',[1 1]);
x1 = [-r, 0, -r*cosd(45), -r*cosd(45); r, 0, r*cosd(45), r*cosd(45)]+cx+1;
y1 = [0, -r, -r*sind(45), r*sind(45); 0, r, r*sind(45), -r*sind(45)]+cy+1;
plot(x1,y1);
hold off

figure;
for i = 0:45:315
    t = linspace(-i,-i-45,128);
    x = [cx, cx+r*cosd(t), cx];
    y = [cy, cy+r*sind(t), cy];
    bw = poly2mask( x, y, size(im,1),size(im,2));
    bw = repmat(bw,1,1,3);
    out = ones(size(im,1),size(im,2),size(im,3)).*155;
    out(bw) = im(bw);
    subplot(2,4,(i/45)+1); imshow(uint8(out));
end;

Results:

Original Image

Partitions drawn over Original Image

Segments of the image

Update

for getting pixel values of the lines, by using Bresenham function from here

figure;
bw1 = zeros(size(im,1),size(im,2));
outmat = zeros(size(bw1));
[X,Y] = bresenham(cx+1-r,cy+1,cx+1+r,cy+1);
ind = sub2ind(size(outmat), Y, X);
outmat(ind) = 1;
[X,Y] = bresenham(cx+1,cy+1-r,cx+1,cy+1+r);
ind = sub2ind(size(outmat), Y, X);
outmat(ind) = 1;
[X,Y] = bresenham(cx+1-r*cosd(45),cy+1-r*sind(45),cx+1+r*cosd(45),cy+1+r*sind(45));
ind = sub2ind(size(outmat), Y, X);
outmat(ind) = 1;
[X,Y] = bresenham(cx+1-r*cosd(45),cy+1+r*sind(45),cx+1+r*cosd(45),cy+1-r*sind(45));
ind = sub2ind(size(outmat), Y, X);
outmat(ind) = 1;
se = strel('disk',5);    %// change the '5' value to affect thickness of the line
outmat = imdilate(outmat,se);
outmat = repmat(boolean(outmat),1,1,3);
outmat1 = zeros(size(outmat));
outmat1(outmat) = im(outmat);
imshow(uint8(outmat1));

Pixel values under each lines

Answer 2

Check the following code. I just did it for a grayscale image. You can now change it to a color image as well. Check and pls confirm this is what you wanted.

clear all;

i = rgb2gray(imread('hestain.png'));
imshow(i);

cr = floor(size(i,1)/2);
cl = floor(size(i,2)/2);

r = min(cr, cl);
a = 90;

r1 = cr;
c1 = size(i,2);
v1=[c1 r1]-[cl cr];

i2 = zeros(size(i,1),size(i,2),ceil(360/a));

for ri = 1:size(i,1)
    for ci = 1:size(i,2)
        v2=[ci ri]-[cl cr];
        a2 = mod(-atan2(v1(1)*v2(2)-v1(2)*v2(1), v1*v2'), 2*pi) * 180/pi;
        d2 = pdist([ci ri; cl cr],'euclidean');
        if d2<=r
            if ceil(a2/a)==0
                a2 =1;
            end
            i2(ri,ci,ceil(a2/a)) = i(ri,ci);
        end
    end
end

figure;
for i=1:360/a
    subplot(2,180/a,i);
    imshow(mat2gray(i2(:,:,i)));
end

Sample output: