How to add a point on an image?

Hello,

So i have the following code:

clear all

clc

% Creating Tabs and properties

fig = uifigure("Name", "BISC");

fig.Resize = 'off'; % Disable resizing

fig.WindowState = 'normal'; % Ensure the window is in normal state (not maximized or minimized)

set(fig, 'Units', 'normalized', 'Position', [0.1, 0.1, 0.8, 0.8]);

tg = uitabgroup(fig, 'Units', 'normalized', "Position", [0, 0, 1, 1]);

t1 = uitab(tg, "Title", "To be added");

t1.Scrollable = "on";

% Adding a button to load the floor plan image

b_loadImage = uibutton(t1, 'Position', [650 550 140 22], 'Text', 'Load Floor Plan');

ax = uiaxes(t1, 'Position', [30 130 600 450]); % Axes to display the floor plan

% Adding a button to detect walls

b_detectWalls = uibutton(t1, 'Position', [650 525 140 22], 'Text', 'Detect Walls');

b_detectWalls.Enable = 'off'; % Disable until an image is loaded

% Adding a button to add points

b_addPoint = uibutton(t1, 'Position', [650 500 140 22], 'Text', 'Add Point');

b_addPoint.Enable = 'off'; % Disable until an image is loaded

% Callback to load image

b_loadImage.ButtonPushedFcn = @(btn, event) loadImage(ax, b_detectWalls, b_addPoint);

% Callback to detect walls

b_detectWalls.ButtonPushedFcn = @(btn, event) detectWalls(ax);

% Callback to add points

b_addPoint.ButtonPushedFcn = @(btn, event) enablePointAdding(ax);

% Functions

% Function to load an image

function loadImage(ax, b_detectWalls, b_addPoint)

% Let user select an image file

[file, path] = uigetfile({'*.jpg;*.jpeg;*.png;*.bmp;*.tif', 'All Image Files'}, 'Select Floor Plan');

if isequal(file, 0)

return;

end

% Display the image on the axes

img = imread(fullfile(path, file));

imshow(img, 'Parent', ax);

% Enable the detect walls and add point buttons

b_detectWalls.Enable = 'on';

b_addPoint.Enable = 'on';

end

% Function to detect walls in the image

function detectWalls(ax)

% Retrieve the image from the axes

imgHandle = findobj(ax, 'Type', 'image');

if isempty(imgHandle)

return;

end

img = imgHandle.CData; % Extract image data

% Convert to grayscale if it's a color image

if size(img, 3) == 3

grayImg = rgb2gray(img);

else

grayImg = img;

end

% Threshold the image to create a binary image

bw = imbinarize(grayImg, 'adaptive', 'ForegroundPolarity', 'dark', 'Sensitivity', 0.4);

% Apply morphological operations

se = strel('rectangle', [5, 5]);

bw = imclose(bw, se); % Close small gaps

bw = imopen(bw, se); % Remove small noise

% Display the processed binary image

imshow(bw, 'Parent', ax);

end

% Function to enable adding points on the image

function enablePointAdding(ax)

% Reset any previous button-down functions

ax.ButtonDownFcn = [];

% Set the ButtonDownFcn of the axes to allow point addition

ax.ButtonDownFcn = @(src, event) addPoint(src, event);

end

% Function to add a point on the image

function addPoint(src, event)

% Get the current point coordinates

cp = event.IntersectionPoint(1:2);

% Plot the point on the axes

hold(src, 'on'); % Keep existing image

plot(src, cp(1), cp(2), 'ro', 'MarkerSize', 10, 'LineWidth', 2);

hold(src, 'off');

% Display the coordinates in the command window (or use for further processing)

disp(['Point added at: X=', num2str(cp(1)), ', Y=', num2str(cp(2))]);

end

But it seems that the point button does not work. Does anyone have a solution to this, i have been trying for quite a while now and can not manage adding a point on my floor plan.

Thank you in advance.

Answer 1

[Ronit]

Hello @ALEXANDROS,

The issue you're experiencing with the point addition feature in MATLAB GUI might be due to how the ButtonDownFcn is being set. The ButtonDownFcn for an axes object can sometimes be overridden by child objects like images. To ensure that clicking on the image triggers the ButtonDownFcn, you need to set the HitTest property of the image to 'off' and ensure the PickableParts property of the axes is set to 'all'.

Modify the loadImage function as follows:

% Set HitTest of the image to 'off' to ensure clicks are registered by the axes
imgHandle = findobj(ax, 'Type', 'image');
set(imgHandle, 'HitTest', 'off');

Additionally, ensure your axes are set to be pickable:

ax.PickableParts = 'all';

Please go through the documentation of Capturing Mouse Clicks for better understanding: https://www.mathworks.com/help/matlab/creating_plots/capturing-mouse-clicks.html

I hope this works for you!

[ALEXANDROS]

Hello @Ronit

Thank you very much for your help!

I followed what you said but as i wanted to be able to add the point after the wall detection, i added

% Set HitTest of the image to 'off' to ensure clicks are registered by the axes
imgHandle = findobj(ax, 'Type', 'image');
set(imgHandle, 'HitTest', 'off');

ax.PickableParts = 'all';

inside the detectWalls(ax) function.

[Ronit]

Yes that will help in selecting points after the wall detection.