It definitely DOES work, but you need to make your mask in the range 0-1. Here's proof:
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clearvars;
workspace; % Make sure the workspace panel is showing.
fontSize = 20;
format compact;
% Read in a standard MATLAB color demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'peppers.png';
fullFileName = fullfile(folder, baseFileName);
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
% Didn't find it there. Check the search path for it.
fullFileName = baseFileName; % No path this time.
if ~exist(fullFileName, 'file')
% Still didn't find it. Alert user.
errorMessage = sprintf('Error: %s does not exist.', fullFileName);
uiwait(warndlg(errorMessage));
return;
end
end
rgbImage = imread(fullFileName);
% Get the dimensions of the image. numberOfColorBands should be = 3.
[rows columns numberOfColorBands] = size(rgbImage);
% Display the original color image.
subplot(2, 2, 1);
imshow(rgbImage, []);
title('Original Color Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]); % Maximize figure.
mask = zeros(rows, columns, 'uint8');
mask(30:300, 50:150) = 1;
% Normalize to 0 - 1.
mask = mask / 255;
% Display the mask.
subplot(2, 2, 2);
imshow(mask, []);
title('Mask', 'FontSize', fontSize);
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask,class(rgbImage)));
% Display the mask.
subplot(2, 2, 3);
imshow(maskedRgbImage, []);
title('MaskedImage', 'FontSize', fontSize);
