Sum of Pixels in an image

Hi,

I have been trying to calculate the Vessel density which is the total image area occupied by the vasculature to the total image area in the binary vessel maps. Here's my code:

I=imread('VAD.png');
figure,imshow(image_read)
I_gray=rgb2gray(I);
figure,imshow(I_gray);
SumPixels = sum(I_gray(:));

T = adaptthresh(I_gray, 0.25);
BW = imbinarize(I_gray,T);
figure,imshowpair(I_gray, BW, 'montage')
Pixels = sum(BW(:));
VAD=Pixels/SumPixels

I am not sure if I am doing it the right way. How should I calculate the sum of pixel occupied by the vessel as the binary conversion gives a whole different value. Any help would be appreciated.

Answer 1

[Walter Roberson]

VAD = Pixels ./ numel(I_gray)