lighthouse.jpg imread into matrix and calculate mean and std? - Homework

Attached it the lighthouse.jpg. I am trying to use imread to load this picture onto a matrix. Then I am trying to calculate and print the mean separately of the red, green, and blue components in the matrix and also the standard deviation for each. I am having trouble getting the mean and std to work.

This is my script.

im1 = imread('Lighthouse.jpg');     % READ IMAGE
imshow(im1);                        % SHOW IMAGE
size(im1);                          % SIZE BY [ROW COLUM COLORMATRIX]
                                    % COLORMATRIX USUALLY 3 WHICH IS FOR
                                    %  RGB, AND SHOWS 3 MATRIXES OF  
                                    % [ROW COLUM] DIMENTIONS.

imr = im1(:,:,1);                   % SHOW TRUE COLOR IMAGING FOR RGB IN SUBPLOTS
img = im1(:,:,2);
imb = im1(:,:,3);
immr = mean(mean(imr));
immg = mean(mean(img));
immb = mean(mean(imb));
imsr = std(std(imr));
imsg = std(std(img));
imsb = std(std(imb));
subplot(3,3,1);
imshow(im1);
subplot(3,3,2);
imshow(immr);
subplot(3,3,3);
imshow(immg);
subplot(3,3,4);
imshow(immb);
subplot(3,3,5);

What happens to be the problem?

[Walter Roberson]

The image did not get attached it appears.

Answer 1

[Image Analyst]

The standard deviation of the standard deviation of the columns is not the standard deviation of the entire image! It's not like the max, min, and mean functions. Try a simple example and you'll see. Just do

imsr = std(imr(:));

to get the standard deviation of an entire array (a single color channel). imr(:) converts the 2D array into a 1D array.

[Nora]

Now I got this error: ?

EDU>> lighthouse
Error using var (line 59)
First argument must be single or double.
Error in std (line 32)
y = sqrt(var(varargin{:}));
Error in lighthouse (line 17)
imsr = std(imr(:,:));

[Nora]

Error:

SuperImpose('lighthouse.jpg','Tulips.jpg','Desert.jpg')
  Undefined function 'resize' for input arguments of type 'uint8'.
  Error in SuperImpose (line 33)
    theSum = theSum + double(resize(thisImage, [smallestRows,
    smallestColumns]));

[Image Analyst]

You need to case varargin to double because var() needs doubles. Use imresize() instead of resize().

[Nora]

Sorry, I answered for a different question. I was still having trouble with the std.

EDU>> lighthouse
Error using var (line 59)
First argument must be single or double.
Error in std (line 32)
y = sqrt(var(varargin{:}));
Error in lighthouse (line 17)
imsr = std(imr(:,:));

[Walter Roberson]

std(double(imr(:)))

Answer 2

[Walter Roberson]

The mean and standard deviations are scalar values; you would not show a scalar value as an image. You might fprintf() the values out on a single line (or two) though.

[Nora]

What does this error mean?

Error in lighthouse (line 17)
imsr = std(std(imr));