Help with regionprops and centroid parts of an image

Hi. I have an image called ROI. I also have the location of the maximum intensity values on a line across the image (shown by red dots)

I wanted to then use these x,y locations to seed a centroid based calculation using region props. I have attempted this, but the values i get are shown by the blue crosses. I can't see my error.

I call my centroid funcion via:

[cenX,cenY,val]=getCentroid(handles,cx(xxx),cy(xxx),ROI);

where cx(xxx) and cy(xxx) are the coordinates of the red dots. My function is:

function [cenX,cenY,val]=getCentroid(handles,xguess,yguess,img)

    %Calculates the centroid by creating a matrix around the guess values
    %on the image img. Also returns intensity at that location
    %n must be odd. Then applies regionprops to calc centroid

    xc=xguess
    yc=yguess
    n=1;  %number of pixels surounding current location (xguess,yguess) to calc centroid
    ROI = img(yc-n:yc+n, xc-n:xc+n)    % This is the ROI (indexing is (ymin:ymax, xmin:xmax)
    C=regionprops(true(size(ROI)), ROI,  'WeightedCentroid');
    CN=C.WeightedCentroid
    cenX=CN(1)+xc
    cenY=CN(2)+yc
    val=ROI(round(CN(1)),round(CN(2)))

(I then want to pass the first and last values of these centroided locations to improfile to obtain a linescan thru the image.)

Answer 1

[Walter Roberson]

      val=ROI(round(CN(2)),round(CN(1)))

It slipped your mind that x is columns not rows.

[Jason]

Thankyou, but also the actual locations seem to be wrong. I have changed them:

CN=C.WeightedCentroid
cenX=CN(2)+xc-1
cenY=CN(1)+yc-1

..but still apear way off.