Intensity Profile of a specific line

Hello,

I want to build an app that lets the user upload an image then draw a line on that image. Then with a press of a button an intensity profile of the specified line will show up next to it.

I'm able to uplad an image but I'm stuck on how to draw a line on top of the image, then just save the location and then intensity afterwards.

Here is a thread of basically what I want to do: https://www.mathworks.com/matlabcentral/answers/389889-how-to-plot-intensity-profile-of-an-image?s_tid=srchtitle

Here's what I have so far:

classdef Intensity_Analysis < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure      matlab.ui.Figure
        PlotButton    matlab.ui.control.Button
        UploadButton  matlab.ui.control.Button
        UIAxes2       matlab.ui.control.UIAxes
        UIAxes        matlab.ui.control.UIAxes
    end

    % Callbacks that handle component events
    methods (Access = private)

        % Button pushed function: UploadButton
        function UploadButtonPushed(app, event)
            global a;
            [filename, pathname] = uigetfile('*.*', 'Pick an Image');
            filename = strcat(pathname,filename);
            a = imread(filename);
            imshow(a,'Parent',app.UIAxes);
        end
    end

    % Component initialization
    methods (Access = private)

        % Create UIFigure and components
        function createComponents(app)

            % Create UIFigure and hide until all components are created
            app.UIFigure = uifigure('Visible', 'off');
            app.UIFigure.Position = [100 100 640 480];
            app.UIFigure.Name = 'MATLAB App';

            % Create UIAxes
            app.UIAxes = uiaxes(app.UIFigure);
            title(app.UIAxes, 'Original Image')
            zlabel(app.UIAxes, 'Z')
            app.UIAxes.Position = [15 173 300 185];

            % Create UIAxes2
            app.UIAxes2 = uiaxes(app.UIFigure);
            title(app.UIAxes2, 'Intensity')
            zlabel(app.UIAxes2, 'Z')
            app.UIAxes2.Position = [314 173 300 185];

            % Create UploadButton
            app.UploadButton = uibutton(app.UIFigure, 'push');
            app.UploadButton.ButtonPushedFcn = createCallbackFcn(app, @UploadButtonPushed, true);
            app.UploadButton.Position = [115 134 100 22];
            app.UploadButton.Text = 'Upload';

            % Create PlotButton
            app.PlotButton = uibutton(app.UIFigure, 'push');
            app.PlotButton.Position = [414 134 100 22];
            app.PlotButton.Text = 'Plot';

            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
    end

    % App creation and deletion
    methods (Access = public)

        % Construct app
        function app = Intensity_Analysis

            % Create UIFigure and components
            createComponents(app)

            % Register the app with App Designer
            registerApp(app, app.UIFigure)

            if nargout == 0
                clear app
            end
        end

        % Code that executes before app deletion
        function delete(app)

            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
    end
end

Answer 1

[Matt J]

You could just use improfile()

https://www.mathworks.com/help/images/ref/improfile.html

[Omor Khan]

Hello Matt,

Thank you for the help. Yes, I do want to use improfile to get the intensity of the image but I want to get the intensity of a specific line/drawing from the user. I found that I can use imfreehand or drawfreehand to have the user draw a line and also see methods that I can store the position in a variable. The issue I'm having is with this current code it won't draw on the image

Updated code below:

% Button pushed function: UploadButton
        function UploadButtonPushed(app, event)
            global a hfH;
            [filename, pathname] = uigetfile('*.*', 'Pick an Image');
            filename = strcat(pathname,filename);
            a = imread(filename);
            imshow(a,'Parent',app.UIAxes);
            hfH = imfreehand();
        end

        % Button pushed function: DrawButton
        function DrawButtonPushed(app, event)
            global x y a hFH;
            binaryImage = hFH.createMask();
            xy = hfH.getPosition;
            structBoundaries = bwboundaries(binaryImage);
            xy=structBoundaries{1}; % Get n by 2 array of x,y coordinates.
            x = xy(:, 2); % Columns.
            y = xy(:, 1); % Rows.
        end

[Matt J]

But improfile does let the user draw the line. Are you saying that non-straight lines need to be supported?

[Image Analyst]

I think he was saying he wants the line to be drawn with drawline() instead of improfile(). I think you could do something like (untested so no guarantees)

hfH = imfreehand();
pos = hfH.Position
delete(hfH); % Delete ROI objects.
hold on;
plot(pos(:, 1), pos(:, 2), 'b-'); % Draw line

[Omor Khan]

Thank you both for the help. I think I'm not explaining it very well, sorry.

I want to make a MATLAB app that lets the user upload the image, then lets the user draw a line on top of the image to specify a location for intensity profile, then plot the intensity profile of the saved location.

Like this image below. There's a line over the image made by the user then with a press of a button the intensity plot will show up.

I undertand that I will be using improfile like this to pass in a line:

improfile(I,x,y);

So the next task is the imfreehand to have the user draw a line then save that position in x and y like this:

hfH = imfreehand();
binaryImage = hFH.createMask();
xy = hfH.getPosition;
structBoundaries = bwboundaries(binaryImage);
xy=structBoundaries{1}; % Get n by 2 array of x,y coordinates.
x = xy(:, 2); % Columns.
y = xy(:, 1); % Rows.

But this step is not going very well for me. Because as soon as I upload the image, once it gets to the hfH part of the code it opens a new figure and have me draw there and not on top of the image :(

@Matt J - From what you explained improfile allows me to do this? I don't know how. This is all new to me. Would you mind showing me how to use it like what you were thinking?

Thanks!

[Image Analyst]

@Omor Khan, bwboundaries returns a cell array (not a structure). First you get xy as the freehand boundary you drew, but then you call bwboundaries() which is totally not necessary because it will just return the same xy you drew with imfreehand.

Not sure why or when your new figure gets opened. You must be calling figure(). Set a breakpoint early and step through it to find out when that extra image gets created.

[Omor Khan]

@Image Analyst, Thank you. I was able to point myself into the right direction and finally understood how to use it. I also changed to drawline() since I only want a line anyway. The issue I'm having now is how to get the position of that drawline to pass into improfile('Image',x,y)

[Matt J]

@Omor Khan From the improfile documentation:

c = improfile lets you select line segments interactively from the image in the current axes. When you finish selecting line segments, improfile returns sampled pixel values along the line segments in c.

[Omor Khan]

@Matt J would you mind showing me a demo of what you mean? I don't think I understand it and how to implement it. Thank you!

[Matt J]

I can't demo it because it is interactive. Just issue the command improfile() at the command line or in a function, while an image axis is current. Then start drawing the profile line on the image.