Fix bounding box in a image and save it

Hi there,

I am trying to fix a Bounding Box permanently in a image because to save it.

I used as usual hold on for graphic the bounding box, but I want to fix it in a image for then save it.

As example:

% Obtain image
krillin = imread("https://es.mathworks.com/responsive_image/150/150/0/0/0/cache/matlabcentral/profiles/22817879_1627284404454.jpg");

% Process it
krillin_grey = im2gray(krillin);
krillin_grey_imadj = imadjust(krillin_grey);
krillin_BW = imbinarize(krillin_grey_imadj);
krillin_BW_2 = imclearborder(~krillin_BW);
% Boca
krillin_BW_2_largest_fin = bwpropfilt(krillin_BW_2, "Area", 1, "largest");

% Obtain the Bounding box
BB_krillboca=regionprops(krillin_BW_2_largest_fin,'BoundingBox');  %<--- rellevant

% Show in the image
imshow(krillin)
hold on
rectangle('Position', BB_krillboca.BoundingBox+[-1 -1 +1 +1], 'EdgeColor','b', 'LineWidth', 1)
hold off

And I want to save just the bounding box in a zeros image:

zeros_krillin = zeros(size(krillin_BW_2_largest_fin));
imshow(zeros_krillin)
hold on
rectangle('Position', BB_krillboca.BoundingBox+[-1 -1 +1 +1], 'EdgeColor','b', 'LineWidth', 1)
hold off

I tried exportgraphics but the size is not the same when it is saved.

Thank you so much

[Josep Llobet]

In this post there was the same question

https://es.mathworks.com/matlabcentral/answers/130657-how-to-save-bounding-box-image

Answer 1

[Saffan]

I understand that you want to save an image along with the bounding box without changing its size. This can be accomplished in the following way:

• Get the figure using “getframe” function.
• Convert it to an image using “frame2im” function.
• Save it using “imwrite” function in the desired format.

Below is an example code snippet that demonstrates how to achieve this:

% Capture the figure with the drawn rectangle
f = getframe(gca);

% Convert it to an image
bounding_box_image = frame2im(f);

% Save the image with the bounding box
imwrite(bounding_box_image, 'bounding_box_image.png');

Refer to these links for more information:

• Write image to graphics file - MATLAB imwrite (mathworks.com)
• Capture axes or figure as movie frame - MATLAB getframe (mathworks.com)
• frame2im - Search - Help Center - MATLAB & Simulink (mathworks.com)