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.

% Demo by Image Analyst.
% Initialization steps.
clc;    % Clear the command window.
fprintf('Beginning to run %s.m ...\n', mfilename);

Beginning to run LiveEditorEvaluationHelperEeditorId.m ...

close all;  % Close all figures (except those of imtool.)
clearvars;
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;

% Read in original image.
rgbImage = imread('lighthouse.png');     % READ IMAGE
[rows, columns, numberOfColorChannels] = size(rgbImage) % SIZE IS [ROWS COLUMNS NUMCOLORs]

rows =    640

columns =    480

numberOfColorChannels =      3

[redChannel, greenChannel, blueChannel] = imsplit(rgbImage);

meanRedValue = mean(redChannel, 'all');
meanGreenValue = mean(greenChannel, 'all');
meanBlueValue = mean(blueChannel, 'all');

sdRed = std(double(redChannel(:)));
sdGreen = std(double(greenChannel(:)));
sdBlue = std(double(blueChannel(:)));

subplot(2, 2, 1);
imshow(rgbImage);
title('Original Image');

subplot(2, 2, 2);
imshow(redChannel);
caption = sprintf('Red Channel.\nMean = %.2f, SD = %.2f', meanRedValue, sdRed);
title(caption);

subplot(2, 2,3);
imshow(greenChannel);
caption = sprintf('Green Channel.\nMean = %.2f, SD = %.2f', meanGreenValue, sdGreen);
title(caption);

subplot(2, 2,4);
imshow(blueChannel);
caption = sprintf('Blue Channel.\nMean = %.2f, SD = %.2f', meanBlueValue, sdBlue);
title(caption);

[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(:)))

[DGM]

inpict = imread('lighthouse.png');
inpict = reshape(inpict,[],size(inpict,3));
channelwisemean = mean(inpict,1)

channelwisemean = 1×3

106.4334 150.0902 171.3984

<mw-icon class=""></mw-icon>

<mw-icon class=""></mw-icon>

channelwisestd = std(double(inpict),0,1)

channelwisestd = 1×3

70.6482 66.4553 87.9043

<mw-icon class=""></mw-icon>

<mw-icon class=""></mw-icon>

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));

Answer 3

[Dimitrios]

can you help me with ghow to get the code for the lighthouse pic and also l,a,b code and pic?

[Walter Roberson]

Lighthouse.jpg appears to be available if you scroll down a little from https://www.mathworks.com/help/images/jpeg-image-deblocking-using-deep-learning.html#JPEGImageDeblockingUsingDeepLearningExample-8

[DGM]

What does "code for the lighthouse pic" mean?

Which lighthouse image is "the lighthouse pic"?

What exactly is the "l,a,b code and pic"?

Here's a lighthouse image and a "LAB code".

% this is the same image as attached by @ImageAnalyst above
rgbpict = imread('lighthouse.png'); % included with IPT
labpict = rgb2lab(rgbpict);

... but there are other standard images of lighthouses.

Either we could spend days guessing what you want, or you could just tell us.

[Dimitrios]

I would like to know where i can find the code for the l, a and b for the lighthouse picture

[Image Analyst]

@Dimitrios, @DGM pretty much already gave you the code. If you'd like a more fleshed out demo, then try this:

% Demo by Image Analyst.
% Initialization steps.
clc;    % Clear the command window.
fprintf('Beginning to run %s.m ...\n', mfilename);

Beginning to run LiveEditorEvaluationHelperEeditorId.m ...

close all;  % Close all figures (except those of imtool.)
clearvars;
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;

% Read in original image.
rgbImage = imread('lighthouse.png');     % READ IMAGE
[rows, columns, numberOfColorChannels] = size(rgbImage) % SIZE IS [ROWS COLUMNS NUMCOLORs]

rows =    640

columns =    480

numberOfColorChannels =      3

[redChannel, greenChannel, blueChannel] = imsplit(rgbImage);
meanRedValue = mean(redChannel, 'all');
meanGreenValue = mean(mean(greenChannel));
meanBlueValue = mean(mean(blueChannel));
sdRed = std(double(redChannel(:)));
sdGreen = std(double(greenChannel(:)));
sdBlue = std(double(blueChannel(:)));

subplot(2, 2, 1);
imshow(rgbImage);
title('Original Image');

subplot(2, 2, 2);
imshow(redChannel);
impixelinfo; % Let user mouse around and see values displayed on the figure.
caption = sprintf('Red Channel.\nMean = %.2f, SD = %.2f', meanRedValue, sdRed);
title(caption);

subplot(2, 2, 3);
imshow(greenChannel);
impixelinfo; % Let user mouse around and see values displayed on the figure.
caption = sprintf('Green Channel.\nMean = %.2f, SD = %.2f', meanGreenValue, sdGreen);
title(caption);

subplot(2, 2, 4);
imshow(blueChannel);
impixelinfo; % Let user mouse around and see values displayed on the figure.
caption = sprintf('Blue Channel.\nMean = %.2f, SD = %.2f', meanBlueValue, sdBlue);
title(caption);

% Convert RGB image into LAB image.
labImage = rgb2lab(rgbImage);
[lImage, aImage, bImage] = imsplit(labImage);

% Display them
figure; % Open up a new window.
subplot(2, 2, 1);
imshow(rgbImage);
title('Original Image');

subplot(2, 2, 2);
imshow(lImage, []);
impixelinfo; % Let user mouse around and see values displayed on the figure.
title('L Image');

subplot(2, 2, 3);
imshow(aImage, []);
impixelinfo; % Let user mouse around and see values displayed on the figure.
title('A Image');

subplot(2, 2, 4);
imshow(bImage, []);
impixelinfo; % Let user mouse around and see values displayed on the figure.
title('B Image');

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[DGM]

@Dimitrios Repeating it doesn't clarify anything. You haven't answered any of the questions I've asked you, so there's nothing new to tell you other than the same guesses. If that's not what you want, you have to explain why.

To repeat:

There are multiple standard images of lighthouses. Which one? Does it matter? If it doesn't matter, why does it even need to be a lighthouse?

If you're asking for "the l, a and b", I have to assume you're talking about CIELAB. If you are, then we've both given you examples. That much might seem obvious, but arguably the most common standard "lighthouse picture" is grayscale, so it's plausible that the request for the LAB image doesn't make sense in context.