Plotting Rectangles Within For Loops

Hello,

I am trying to run a color detection algorithm. To do this, I used the regionprops command and detected the center of N number of flowers within an image. I then used the impixel command to detect the RGB values on this centroid. The program works by detecting the boundaries of all flowers found within the image. This number is denoted N.

What I wish to do is generate a square around this centroid point of the square (circle will also work) where I can take the average of all the RGB values. Once I have this average, I can compute what color the square is. Here is where I am having trouble:

Although I have detected the flowers and their centroid, I am unable to generate a square around each individual flower. Here is the code I am using: range_x = range(boundary_matrix(:,1)); range_y = range(boundary_matrix(:,2));

        range_boundary_x = range_x/4;
        range_boundary_y = range_y/4;
        for N = 1:N

            %FOR X

            outer_range_x = round(range_boundary_x + centroid_matrix(N,1));
            inner_range_x = round(-range_boundary_x + centroid_matrix(N,1));

            %FOR Y

            outer_range_y = round(range_boundary_y + centroid_matrix(N,2));
            inner_range_y = round(-range_boundary_y + centroid_matrix(N,2));

            centroid_point = impixel(cam_image_rgb,centroid_matrix(N,1),...
                centroid_matrix(N,2));
            Red = centroid_point(1);
            Green = centroid_point(2);
            Blue = centroid_point(3);
            color_matrix(N,:) = [Red, Green, Blue];
            hold on;
            rectangle('Position', [inner_range_x,inner_range_y,...
                outer_range_x - inner_range_x,...
                outer_range_y - inner_range_y])
            hold on;

        end
end

Currently, what is happening is that the code is plotting the individual rectangles around each flower; however, since each flower is a different size - I want to make it so that each flower has its own rectangle. What is happening right now is that each flower is getting N rectangles (with each rectangle being a different size).

[Walter Roberson]

Is your mention of range() there, the Stats Toolbox range function,

http://www.mathworks.com/help/toolbox/stats/range.html

Using

for N=1:N

is probably not a good idea: inside the loop, which value should N refer to?

[Jake Bolanski]

Right, range is the statistical toolbox function which gives me X_max - X_min or Y_max - Y_min.

The reason I am using a loop inside the loop, like I have set up, is so that I can plot the centroids for each flower. While this makes no sense, it doesn't work when it is not inside its own nested loop. Any ideas on how I would go about making a square around the centroid as explained earlier?

Current set up is:

for weeds_detected = 1:N

...

...

...

for N = 1:N

%FOR X

outer_range_x = round(range_boundary_x + centroid_matrix(N,1));

inner_range_x = round(-range_boundary_x + centroid_matrix(N,1));

%FOR Y

outer_range_y = round(range_boundary_y + centroid_matrix(N,2));

inner_range_y = round(-range_boundary_y + centroid_matrix(N,2));

centroid_point = impixel(cam_image_rgb,centroid_matrix(N,1),...

centroid_matrix(N,2));

Red = centroid_point(1);

Green = centroid_point(2);

Blue = centroid_point(3);

color_matrix(N,:) = [Red, Green, Blue];

hold on;

plot(centroid_matrix(N,1),centroid_matrix(N,2),...

'--rs','LineWidth',2,...

'MarkerEdgeColor','k',...

'MarkerFaceColor','g',...

'MarkerSize',10)

hold on;

centroid_rect = rectangle('Position', ...

[inner_range_x,inner_range_y,...

outer_range_x - inner_range_x,...

outer_range_y - inner_range_y]);

get(centroid_rect)

hold on;

end

end

[Walter Roberson]

If you have a nested "for" loop then we are going to need to see all relevant code.

You should not use

for N=1:N

as that is plain confusing. Notice you are using the same name on the left side as you are using as the boundary condition on the right side. Inside the loop, it becomes ambiguous to readers as to whether N should refer to the current iteration or should refer to the number of items.

Answer 1

[Jake Bolanski]

Thanks Walter, it turns out that the nested for loop, indeed, was causing the triple printing of the rectangles. Having removed it, the code seems to work flawlessly in this regard :)