How to include manual click control in imaging algorithm?

Hello, I am trying to create a program where after I load an image and display it, I can manually click on the image and return the pixel intensity values in a defined kernel. Please help me understand how to implement this click control and specify the shape of the kernel. cheers

Answer 1

[Bruno Pop-Stefanov]

You can use ginput to select a pixel from an image displayed in an axes. ginput returns the x and y coordinates of the location where the user clicked. You can use these coordinates to get the intensity value at that location.

For example:

1. Read image in

    I = imread('coins.png');

2. Display image

    figure
    imagesc(I)
    colormap(gray)

3. Ask the user to select 1 point

    [x,y] = ginput(1);

4. Round the coordinates to the nearest pixel

    x = round(x);
    y = round(y);

5. Return the intensity value at that location

    intensityValue = I(y,x)

As for defining kernels, I am not sure what you mean. Do you mean that you would like to define a region in an image using the mouse?

If yes, then you can use the roipoly function to draw a polygon in the image. The function returns the region as a binary mask. You can then use this mask to get the average intensity over the specified region.

For example:

1. Read image in

    I = imread('coins.png');

2. Display image

    figure
    imagesc(I)
    colormap(gray)

3. Ask the user to draw a polygon in the image

    mask = roipoly;

4. Get all the intensity values for the specified region

    intensityValues = I(mask);

5. Compute the mean of these values

    averageIntensityValue = mean(intensityValues);

Answer 2

[Image Analyst]

Try me freehand drawing demos. One of them gives you the mean in a region you traced out over the image.