Not understanding a simple code.

I am new in image processing and matlab as well. After searching for hours, I have failed to find what this code actually does.

I = imread('6.tif');
I = I(1:200,1:200,:);

I understand the first line is reading the image file. but the next one is confusing to me.

Please any one help me to get this. any broad explanation will be helpful for me.

Answer 1

[Image Analyst]

It gets rows 1 to 200, and columns 1 to 200, and all 3 color channels (the third index, that's what the : means. It means "all").

[Image Analyst]

Basically it's cropping the image.

[Abdur Rahim]

Great! Thanks. I understood the fact. But when I try to make it gray(rgb2gray), an error occurred.

| |RGB must be a m x n x 3 array.| |

Is not my image is RGB? i am using a black and white image.

[Image Analyst]

Here is more robust code:

I = imread('6.tif');
[rows, columns, numberOfColorChannels] = size(I);
if numberOfColorChannels == 3
  I = rgb2gray(I);
  if rows > 200 && columns > 200
    I = I(1:200,1:200,:); % Crop all 3 channels.
  end
else
  if rows > 200 && columns > 200
    I = I(1:200,1:200); % Crop single channel.
  end
end

[Abdur Rahim]

Great work! I have got what is going on!!