MATLAB: How to obtain image intensity values of images

Question

I want to obtain image intensity values at any three selected points of the original eight.tif image.

Answer 1

Try impixel() or just indexing

intensity1 = grayImage(y1, x1);
intensity2 = grayImage(y2, x2);
intensity3 = grayImage(y3, x3);

x and y are any INTEGER values that you want inside the boundaries of the image. If you need to user to select them, use ginput(3);

[x,y] = ginput(3); % User to select 3 points.
x = int32(x); % Round and cast to integer.
y = int32(y);
intensity1 = grayImage(y(1), x(1));
intensity2 = grayImage(y(2), x(2));
intensity3 = grayImage(y(3), x(3));