How to make a select-able grid

I need some guidance on how to make a selectable grid. I need to make a GUI that allows people to select a box on a grid over an image and make it change colors. So say I have a 25x25 grid over an image. if a person clicks on box 13,20 that box should change to blue. How do i do that?

Answer 1

[KSSV]

    N = 25 ;
    x = linspace(0,1,N) ;
    y = linspace(0,1,N) ;
    [X,Y] = meshgrid(x,y) ;
    coor = [X(:) Y(:)] ;

I = imread('cameraman.tif');
image([0 1],[0 1],I) 
hold on
plot(X,Y,'k') ; 
plot(X',Y','k') ;

    count = 0 ;
    while count == 0
        [x,y] = ginput(1) ;

        idx = knnsearch(coor,[x y],'k',4) ;
        % form bounding box
        x0 = min(coor(idx,1)) ;x1 = max(coor(idx,1)) ;
        y0 = min(coor(idx,2)) ;y1 = max(coor(idx,2)) ;
        % square points
        coori = [x0 y0 ; x0 y1 ; x1 y1 ; x1 y0 ; x0 y0] ;
        patch(coori(:,1),coori(:,2),'b') ;

    end

[Anonymous Matrix]

Thanks! that's exactly what i need. But one more question... How do I get the background to be my image? because right now it's a white background but i need to color boxes to cover my image.

[KSSV]

Code edited...check it..

[Anonymous Matrix]

thanks!

[Matus Drexler]

Hi.

Is it possible to select possition by e.g. mouse moving with left click?

[Mauricio Pereira]

Hello. How could I code for selecting multiple boxes of the grid at once? For example, click one box of the grid while leaving pressed down the mouse, and finally releasing it.