How to plot the brightness lines in Matlab, as this picture?

Higher dense the path, higher brighness shown on the figure.

Answer 1

[Image Analyst]

If you have an image, that starts out as all zeros, and a set of coordinates that define where the lines go, you can simply add 1 to the image everytime you encounter one of those coordinates. Like if you have a set of (x,y) coordinates of a line (perhaps use Bresenham's line algorithm ) then do this

heatmapImage = zeros(rows, columns)
for k = 1 : length(x)
    row = round(y(k));
    col = round(x(k));
    % Don't let go outside image.
    if row > rows
        row = rows;
    end
    if col > columns
        col = columns;
    end
    if row < 1
        row = 1;
    end
    if col < 1
        col = 1;
    end
    % Increment the value.
    heatmapImage(row, col) = heatmapImage(row, col) + 1;
end

Repeat that for every set of x,y data you have, then display the resulting image:

imshow(heatmapImage, []);
colormap(jet(256));
colorbar;

Answer 2

[Walter Roberson]

This style is sometimes called a "heat map"

http://www.mathworks.com/matlabcentral/answers/224454-creating-a-heatmap-to-visualize-denisity-of-2d-point-data#answer_183261

https://www.mathworks.com/matlabcentral/fileexchange/47165-heatscatter-plot-for-variables-x-and-y

https://www.mathworks.com/matlabcentral/fileexchange/31726-data-density-plot

https://www.mathworks.com/help/bioinfo/ref/heatmap.html