But isn't the fun of it doing it yourself? Well, I have a demo that does most of it for you. You just have to draw the box, resize to the box and figure out how to shift the mask. But this is a good place to start:
[ Edit] Now it does all that for you.
clc; % Clear the command window.
clearvars;
close all; % Close all figures (except those of imtool.)
imtool close all; % Close all imtool figures.
workspace; % Make sure the workspace panel is showing.
fontSize = 20;
format compact;
% Change the current folder to the folder of this m-file.
if(~isdeployed)
cd(fileparts(which(mfilename)));
end
% 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
% Read in a standard MATLAB color demo image.
folder = 'C:\Users\Light\Documents\Temporary';
baseFileName = 'awrdd5.jpg';
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
% Read image from disk.
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, 3, 1);
imshow(rgbImage, []);
axis on;
title('Original Color Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Read in second image.
baseFileName = 'man.jpg';
fullFileName = fullfile(folder, baseFileName);
rgbImage2 = imread(fullFileName);
% Display the second color image.
subplot(2, 3, 2);
imshow(rgbImage2, []);
axis on;
title('Second Color Image', 'FontSize', fontSize);
% Ask user for location using imrect() or rbbox().
subplot(2, 3, 2); % Switch back to first image.
promptMessage = sprintf('Draw a box over the original (first) image');
button = questdlg(promptMessage, 'Draw box', 'OK', 'Cancel', 'OK');
if strcmp(button, 'Cancel')
return;
end
k = waitforbuttonpress;
point1 = get(gca,'CurrentPoint'); % button down detected
finalRect = rbbox; % return figure units
point2 = get(gca,'CurrentPoint'); % button up detected
point1 = point1(1,1:2); % extract x and y
point2 = point2(1,1:2);
p1 = min(point1,point2); % calculate locations
offset = abs(point1-point2); % and dimensions
xCoords = [p1(1) p1(1)+offset(1) p1(1)+offset(1) p1(1) p1(1)];
yCoords = [p1(2) p1(2) p1(2)+offset(2) p1(2)+offset(2) p1(2)];
x1 = round(xCoords(1));
x2 = round(xCoords(2));
y1 = round(yCoords(5));
y2 = round(yCoords(3));
% Plot the mask as an outline over the image.
hold on;
plot(xCoords, yCoords, 'linewidth', 2);
% Resize rgbImage2
% Call to imresize()
% Here, I'll just resize to size of the box.
newRows = abs(y2-y1)+1;
newColumns = abs(x2-x1)+1
rgbImage2 = imresize(rgbImage2, [newRows newColumns]);
[rows2 columns2 numberOfColorBands2] = size(rgbImage);
% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
% Same, but this time for the second image.
redChannel2 = rgbImage2(:, :, 1);
greenChannel2 = rgbImage2(:, :, 2);
blueChannel2 = rgbImage2(:, :, 3);
% Get the mask - it's where the red channel is brighter than 55.
mask = greenChannel2 < 171; % A logical image.
% Fill in holes
mask = imfill(mask, 'holes');
% Display the mask image.
subplot(2, 3, 3);
imshow(mask, []);
title('Binary Mask', 'FontSize', fontSize);
axis on;
% Multiply the mask by the images to get just the football
% and not the background.
maskedRed = redChannel2 .* uint8(mask);
maskedGreen = greenChannel2 .* uint8(mask);
maskedBlue = blueChannel2 .* uint8(mask);
% Stack all the color channels back into the 3D true color image.
maskedRgbImage = cat(3, maskedRed, maskedGreen, maskedBlue);
% Display the masked second color image.
subplot(2, 3, 4);
imshow(maskedRgbImage, []);
axis on;
title('Masked Color Image', 'FontSize', fontSize);
% Make a large mask for the original picture.
bigMask = false(size(redChannel));
% Now insert the small mask into it.
bigMask(y1:y2, x1:x2) = mask;
% Insert rgbImage2 into rgbImage.
% Assign only image pixels, not background pixels.
redChannel(bigMask) = redChannel2(mask);
greenChannel(bigMask) = greenChannel2(mask);
blueChannel(bigMask) = blueChannel2(mask);
rgbImage3 = cat(3, redChannel, greenChannel, blueChannel);
% Display the second color image.
subplot(2, 3, 5);
imshow(rgbImage3, []);
axis on;
title('Output Color Image', 'FontSize', fontSize);
msgbox('Done with demo. Thanks ImageAnalyst!');
