hi,, i'm new in matlab.. i want to draw using the mouse with this code, but this code can only make one line,, i want to make it more..,

hFH = imfreehand (); % Get the xy coordinates of where they drew.

xy = hFH.getPosition; % get rid of imfreehand remnant.

delete(hFH); % Overlay what they drew onto the image.

hold on; % Keep image, and direction of y axis.

x = xy(:, 1);

y = xy(:, 2);

% X = [X x];

% Y = [Y y];

line(x, y, 'Color','k','LineWidth', 4);

Answer 1

[Kan-Hua]

Hi,

The simplest way is initialising an axes object that imfreehand() function can draw on to, and put your function into an infinite loop, like this:

ax=axes();

while true
    hFH = imfreehand(ax); % Get the xy coordinates of where they drew. 
    xy = hFH.getPosition; % get rid of imfreehand remnant.
    delete(hFH); % Overlay what they drew onto the image.
    hold on; % Keep image, and direction of y axis.
    x = xy(:, 1);
    y = xy(:, 2);
    % X = [X x];
    % Y = [Y y];
    line(x, y, 'Color','k','LineWidth', 4);
end

Is this what you are looking for?

[Hendri Setiawan]

thank you, sir...

right, like that,,

but.., when I close the figure, there is an error message like this:

??? Too many outputs requested. Most likely cause is missing [] around left hand side that has a comma separated list expansion.

Error in ==> imfreehand>imfreehand.getPosition at 95 pos = obj.api.getPosition();

Error in ==> Untitled at 5 xy = hFH.getPosition; % get rid of imfreehand remnant.

how i can fix this error??

[Image Analyst]

Why'd you accept it then? With my demo there is no such error. Check out my demos to see how it should be done.

[Kan-Hua]

The error message happens because the function iamfreehand() is waiting for your response, but the user close the figure to end the program, so iamfreehand() function cannot return any output to hFH. This does not affect the program itself, but if you are really bothered by the error message, you can add a try/catch to catch that error message, like this:

close all;
ax=axes();

while true
    try
    hFH = imfreehand(ax); % Get the xy coordinates of where they drew. 
    xy = hFH.getPosition; % get rid of imfreehand remnant.
    catch err
        if strcmp(err.identifier,'images:roiParseInputs:invalidHandle');
            disp('program exit');
            break;
        end
    end

    delete(hFH); % Overlay what they drew onto the image.
    hold on; % Keep image, and direction of y axis.
    x = xy(:, 1);
    y = xy(:, 2);
    % X = [X x];
    % Y = [Y y];
    line(x, y, 'Color','k','LineWidth', 4);
end

In Image Analyst's code, he set a dialog to ask whether the user want to continue in his main loop, so he can avoid this error message.

To Image Analyst: Thank you for your code though. I actually learned a lot from your code. :)

Answer 2

[Image Analyst]

See my demos of imfreehand, attached.