How to make continuous contour line discrete?

Dear all,

I have a contour of a circle. I want to decimate (downsample) it to 50 samples of original contour. What is the best way of doing it. Right now I have 51 sample instead of 50 due to ' floor ' function.

Here is the code I'm using right now:

    close all; clear all;clc;
    o_circ = imread('circle.jpg');
    bw_circ = im2bw(o_circ, graythresh(o_circ));
    cont = contour(bw_circ, [0,0], 'r.',...
                    'LineWidth',2); close;
    [row, col]=size(cont);

    down_cont1=downsample(cont(1,:),floor(col/50),1); down_cont2=downsample(cont(2,:),floor(col/50),1);

    figure; ax1=subplot(1,2,1); imshow(o_circ); hold on; cont = contour(bw_circ, [0,0], 'r.',...
        'LineWidth',2);  title('Original contour');
    ax2=subplot(1,2,2); imshow(o_circ); hold on; plot(down_cont1, down_cont2, 'r*',... 
        'LineWidth',2); title('Downsampled contour'); axis([ax1 ax2],'tight');

And here is the result:

Thanks in advance for any help!