Creating Binary Image from Polygon Label in MATLAB

Hello,

I'm relatively new to MATLAB and I'm working on a project where I need to create a binary image from a PNG image. I've used the Image Labeler app to add a polygon label to the region of interest in my image, similar to what's shown in the attached image.

Now, I'm looking for guidance on the next steps to create a binary label. Specifically, I want the selected polygon area to be in white, while the rest of the image should be black. After creating this binary label, I'd like to export it as a PNG file.

I've searched extensively for a solution but haven't been able to figure it out yet. Can someone please provide me with step-by-step instructions or sample code on how to achieve this in MATLAB?

Any assistance would be greatly appreciated. Thank you!

Answer 1

[Image Analyst]

You have to click the Export button and then export to the workspace to a variable, like groundTruth. Then you can get the (x,y) coordinates from groundTruth.Labeldata.yourRegionm then use poly2mask and imwrite.

x = groundTruth.LabelData.yourRegion(:, 1);
y = groundTruth.LabelData.yourRegion(:, 2);
mask = poly2mask(x, y, rows, columns);
imwrite(mask, 'Mask.png');

I don't think there is a way to export it directly without writing some code like I did.

[Ahmad]

thank you!

[Image Analyst]

Thanks for accepting. You can email them and make the suggestion that the labeled image be able to be exported to a disk file.

Answer 2

[Sulaymon Eshkabilov]

Here is how it can be done:

I0 = imread('HVOF.png');
I = rgb2gray(I0);
% Polygon coordinates
XY=[50 150; 200 250; 300 350; 150 350; 100 350;50 150;]; % Close the loop polygon           
X = XY(:,1)';% Coordinates of the polygon along x axis
Y = XY(:,2)';% Coordinates of the polygon along y axis
[rows, columns, numberOfColorChannels] = size(I);
figure
imshow(I, []);
axis 'on';
title('ALPS (Original picture)')
hold on;
plot(X, Y, 'rd-', 'LineWidth', 2);

mask = poly2mask(X,Y, rows, columns);
% Beyond of the MASK (polygon) = black (0)
Inew = I;
Inew(~mask) = 0;
figure('name', 'Comparison')
subplot(221)
imshow(I), title ('Original'), axis on
subplot(222)
imshow(Inew), title('Changed')

figure ('Name', 'Changed Image')
imshow(Inew), title('Changed')
axis('on', 'image')

[Ahmad]

Thank you for responding. I want to make polygons through the image labeler and not using the code. Can you tell me how it can be done?