Try this:
grayImage = imread('moon.tif');
[rows, columns, numberOfColorChannels] = size(grayImage);
% Get the dimensions of the image.
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(grayImage)
if numberOfColorChannels > 1
% It's not really gray scale like we expected - it's color.
% Use weighted sum of ALL channels to create a gray scale image.
grayImage = rgb2gray(grayImage);
% ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
% which in a typical snapshot will be the least noisy channel.
% grayImage = grayImage(:, :, 2); % Take green channel.
end
imshow(grayImage, []);
axis on;
verticalProfile = mean(grayImage, 2);
horizontalProfile = mean(grayImage, 1);
hold on;
% Plot horizontal profile.
x = 1 : columns;
amplitude = 2; % Scaling factor
y = rows - amplitude * horizontalProfile;
plot(x, y, 'r-', 'LineWidth', 2);
% Plot vertical profile.
y = 1 : rows;
amplitude = 1; % Scaling factor
x = columns - amplitude * verticalProfile; % To plot on RIGHT side
x = amplitude * verticalProfile; % To plot on LEFT side
plot(x, y, 'm-', 'LineWidth', 2);
If you'd rather, you can do
verticalProfile = grayImage(:, columnIndex);
horizontalProfile = grayImage(rowIndex, :);
where you specify the row and column where you want the profile to go through.
