How “size(x,3)>1” works on an image?

 x=imread('a.jpg');

 if (size(x,3)>1)%if RGB image make gray scale

 try

 x=rgb2gray(x);%image toolbox dependent

 catch

 x=sum(double(x),3)/3;%if no image toolbox do simple sum

 end

 end

I don’t understand the if condition. How “size(x,3)>1” works on an image? Can anyone please help me?

Answer 1

[Thomas]

size(x,3) - if it is greater than 1 than it is a color RGB image.

try size(x) and see - if you get two dimensions its grayscale if you get three dimensions its RGB and that is exactly what your code is looking for ( if its color RGB convert to grayscale)

Answer 2

[Image Analyst]

I prefer the more explicit:

% Get the dimensions of the image.  
% numberOfColorBands should be = 1 or 3 depending if image is grayscale or RGB.
[rows, columns, numberOfColorBands] = size(grayImage);
if numberOfColorBands > 1
  % It's not really gray scale like we expected - it's color.
  % Convert it to gray scale by taking only the green channel.
  grayImage = grayImage(:, :, 2); % Take green channel.
end

Here is how to check if you have the Image Processing Toolbox installed:

% Check that user has the Image Processing Toolbox installed.
hasIPT = license('test', 'image_toolbox');
if ~hasIPT
  % User does not have the toolbox installed.
  message = sprintf('Sorry, but you do not seem to have the Image Processing Toolbox.\nDo you want to try to continue anyway?');
  reply = questdlg(message, 'Toolbox missing', 'Yes', 'No', 'Yes');
  if strcmpi(reply, 'No')
    % User said No, so exit.
    return;
  end
end