Exclude from plotting some coordinates (born from blank .png images)

Hello! Maybe the title will not be well clear but I hope I am clear in my goal.

I have the attached code along with some .png figures.

What I want to achieve is the figure below though with the exclusion of those nodes that are created when a "white" .png image is read (.png image with no black curve).

I also want to keep the position of the white .png image with that Y coordinate (z in the code).

I had thought about the "isempty" command but I am not clear where and how to use it in my code (and also if it is suitable to use it).

I hope I have been clear. I thank to those who can help me.

[Fifteen12]

Hi Alberto, I'm not sure I know what you're trying to do--are you trying to parse PNGs? How are these nodes arising? Can you share more information about what is causing these nodes to occur?

Answer 1

[DGM]

One simple way to skip plotting those cases would be to just do this modification:

for k = 1:length(imageFiles)
    baseFileName = imageFiles(k).name;
    fullFileName = fullfile(myFolder, baseFileName);
    fprintf('Now reading %s\n', fullFileName);
    imageArray = imread(fullFileName);
    
    binaryImage = imageArray;
    binaryImage = ~binaryImage;
    M1 = function_verification_code(binaryImage);
    
    % only plot if there's more than one point
    if size(M1,1)>1
        % Switch to the figure for the 3-D plotting:
        figure(hFig3);
        
        current_z = z(k) * ones(size(M1, 1), 1);
        plot3(M1(:, 2), current_z, M1(:, 1), 'b.');
        
        hold on
        drawnow;   
    end
end