Trying to find the Area of the boundary box? Help thanks~

As stated in the title, I require help on trying to find the area of the boundary which I will be using to compare with several condition to obtain my result.

Here is a sample of my processed image which have the boundary box and the centroid.

If possible, if anyone could, finding the area of the white region is much appreciated too as it is more accurate than calculating the area of the boundary box.

Thank you.

Regards, Akira

Answer 1

[Walter Roberson]

regionprops() 'Area' will find the number of non-zero pixels in the region. If you regionprops() 'BoundingBox' then the area of the bounding box is the product of the last two values. Bounding box is of the form

[x y width height]

so multiply the last two values.

[Akira Chan]

Thank you very much for your quick reply Mr Walter, but I am still not very sure on how to do that, is there a place where I can see some example of this implementation? Thank you.

I found some example from the matlab code itself but I need a deeper understanding.

[Walter Roberson]

stats = regionprops(YourBinaryImage, 'Area', 'BoundingBox');
for K = 1  : length(stats)
  bb = stats(K).BoundingBox;
  barea = bb(3) * bb(4);
  fprintf('Area #%d x = %d y = %d width = %d height = %d true area %d region area %d\n', K, bb(1), bb(2), bb(3), bb(4), stats(K).Area, barea);
end

[Akira Chan]

Thank you very much, sir Walter. This is exactly what I needed!! Thank you again! :) It seems I just missed the printf function, no wonder I don't see the width and height, oh silly me. xD

[oza san]

Dear walter Roberson i use open source code in the following link https://www.mathworks.com/help/vision/examples/automatically-detect-and-recognize-text-in-natural-images.html and i get the figure below i need to extract those regions in the bounding box and save each with different name mind you if you can help me?

[Walter Roberson]

Use the bounding box returned by regionprops as information for imcrop() of the color region.

Do not save each of them as a different workspace variable; http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

At worst save them as different field names of a struct and then use save() with the -struct option to write the fields to separate variables in a .mat file.

[oza san]

ok thank you

[oza san]

dear walter hope all id fine with u!!!here i am again I have to detect text from images and i have to compare the results found with the ground truth. How i can prepare aground truth for text regions in the image?the coordinates need are x,y,width and height of the text regions in the image?