I'm trying to transform a colored imaged to gray scale without using the function rgb2gray?

I am having difficulties with N and M because when it runs through the loop, it cannot read since the index is out of bounds. What does N and M represent instead? Thanks in advance!

function [img_out] = myGreyScale(img_in)

img=double(imread(img_in))/255;

N= 1:255;

M=1:255;

for i = 1:N

    for j= 1:M

        a=img_in(i,j,1);

        b=img_in(i,j,2);

        c=img_in(i,j,3);

        d=(a+b+c)/3;

        img_out(i,j,1)=d;

        img_out(i,j,2)=d;

        img_out(i,j,3)=d;

    end

end

end

Answer 1

[Image Analyst]

Change the lines to

a=img_in(i,j,1);
b=img_in(i,j,2);
c=img_in(i,j,3);
d=(a+b+c)/3;
img_out = uint8(d);

No loops needed.

[Christopher]

what is i and j then?

[Image Analyst]

Sorry - I forgot to delete them

a=img_in(:,:,1);
b=img_in(:,:,2);
c=img_in(:,:,3);
d=(a+b+c)/3;
img_out = uint8(d);

Use : (meaning "all") instead.