test1

rgb1 = imread('test.png');
v = rgb1(60,60:120:360,1:3)
imshow(rgb1);

v(:,:,1) =

  200    0    0


v(:,:,2) =

    0  200    0


v(:,:,3) =

    0    0  200

rgb2 = imread('gray.png');
v = rgb2(60,60:120:360)
imshow(rgb2);

v =

   33  105    9

% from Java getRGB function
v = [ 101  173  53 ]

v =

   101   173    53

rgb3 = imread('test2.png');
v3 = rgb3(60,15:30:360)
imshow(rgb3);

v3 =

    0   21   42   63   85  106  127  148  170  191  212  233

rgb4 = imread('gray2.png');
v4 = rgb4(60,15:30:360)
imshow(rgb4);

v4 =

    0    2    6   13   23   37   54   75  103  133  168  208

plot(v3,v4);
xlabel('color png');
ylabel('Java converted grayscale');

v = [0.2989 0.5870 0.1140];
sum(v)
nv = round(v*1024)
sum(nv)

% imageinfo('gray2.png')

ans =

    0.9999


nv =

   306   601   117


ans =

        1024