hello all. I realy need help in coding with matlab. I try to built an object recognation with ANN and i need some value for the input node. the problem is I don't know how to extract it. here are some of my problem :
1. how can I get the RGB value from one pixel. and I want to get the each of value ( each value of R,G and B)

2. how can I change the color of pixel in image? my image was using a solid white background. and now I want to make change like this :
"all pixel with white color change to black and all pixel that not white color change to white". i use code like this but it failed

for c =1: 480000
if b (c) > 250
b(c) = 0;
else
b(c) = 255;
end
end;

3. As you can see in my code above I use an single looping. how can I change this code into matlab code

for i = 1 to 800
for j = 1 to 600
if b [i][j] > 250
b[i][j] = 0;
else
b [i][j] = 255;
in other word I want to know how to access array row and column in matlab.

thanks very much. sorry if my post is extremly long, but I'm desperate in need of help

please have a look in help of matlab

there is a function im2bw and imcomplement for the purpose

when the pixel is white there is no need of intensity having 255 it can be 1 as well that is BW