Plot intensity minima with improfile

I currently have code that calculates the gradient along line segments I've drawn on an image and plots them using improfile. How can I retrieve the coordinates of the improfile minima? Even better, how can I also plot them on the graph as points? Any help would be greatly appreciated!

for j = 1:10
             points_x(j) = (x(1) * j + x(2) * (11 - j))/11;
           points_y(j) = (y(1) * j + y(2) * (11 - j))/11;

             line_x(j) = points_x(j) - x(1);
             line_y(j) = points_y(j) - y(1);
             v = [line_x(j), line_y(j)];

             normal_x = linspace(points_x(j) + v(2), points_x(j) - v(2), 200);
             normal_y = linspace(points_y(j) - v(1), points_y(j) + v(1), 200);

             subplot(5, 2, j);
             improfile(I, normal_x, normal_y), grid on;
             title(['Voxel Gradients along Ray ' num2str(j) ' '])
             xlabel('x')
             ylabel('y')
             zlabel('Intensity')

        end