How to get onclick coordinate pixel value and location from an image in Matlab?

Question

I want to get some location(x,y) and corresponding pixel value after clicking on image (out of multiple images) and store it in an array . Any ideas how i can achieve this in Matlab ? For example I click on 231,23 (X,Y) coordinates and it has pixel value of 123 and image is 1.jpg. my first three elements of array would be 231 , 23 , 123 , 1

Answer 1

You could either use ginput or specify a ButtonDownFcn

The following will record points until you hit enter.

fig = figure();
img = rand(50);

imshow(img)

[x,y] = ginput();

% Get the pixel values
data = img(sub2ind(size(img), round(y), round(x)));

Below is an example using the ButtonDownFcn callback

fig = figure();
img = rand(50);

hax = axes('Parent', fig);
him = imshow(img, 'Parent', hax);

% Specify the callback function
set(him, 'ButtonDownFcn', @(s,e)buttonDown(hax, img))

function buttonDown(hax, img)
    % Get the location of the current mouse click
    currentPoint = get(hax, 'CurrentPoint');
    currentPoint = round(currentPoint(1,1:2));

    % Retrieve the pixel value at this point
    data = img(sub2ind(size(img), currentPoint(2), currentPoint(1)));

    % Print the data to the command window.
    fprintf('x: %0.2f, y: %0.2f, pixel: %0.2f\n', ...
            currentPoint(1), currentPoint(2), data);
end