Rectangle around the object, Bounding box,

Hello, I used this code to make rectangle around the object at binary image:

st = regionprops(BW, 'BoundingBox' );

figure, imshow('MY_IMAGE.jpg')

 rectangle('Position',[st.BoundingBox(1),st.BoundingBox(2),st.BoundingBox(3),st.BoundingBox(4)],...
'EdgeColor','r','LineWidth',2 )

but if I have more than one object, this code doesn't working How can I draw N rectangles for N objects on image? Thank you

[sukku]

I want to find out an region properties of below image

[Image Analyst]

Use regionprops(). See my Image Segmentation Tutorial where I cover all that code.

[Kimo Kalip]

The image segmentation strategy included in that tutorial works great for well defined, solid images on a relatively consistent background. However, what do you do when you're trying to work with objects that aren't perfectly defined or shaped? Like what if you had something with various holes like a slinky or spring?

[Image Analyst]

Well that's where the art of designing an image analysis algorithm comes in. You're right - it's not so straightforward and easy. That's what keeps people like me employed.

Answer 1

[Image Analyst]

Put it in a loop (untested)

for k = 1 : length(st)
  thisBB = st(k).BoundingBox;
  rectangle('Position', [thisBB(1),thisBB(2),thisBB(3),thisBB(4)],...
  'EdgeColor','r','LineWidth',2 )
end

[Felix]

It is good! thank you!

[Rupali]

thanks a lot

[Explorer]

INPUT IMAGE:

___________________________________________________________________________ MATLAB CODE: ___________________________________________________________________________ clear all; close all; clc image=imread('a_ASL3.jpg'); BW=binary_image(image); BW = ~BW; st = regionprops(BW, 'BoundingBox' ); for k = 1 : length(st) thisBB = st(k).BoundingBox; rectangle('Position', [thisBB(1),thisBB(2),thisBB(3),thisBB(4)],... 'EdgeColor','r','LineWidth',2 ) end ___________________________________________________________________________

OUTPUT IMAGE:

___________________________________________________________________________ Problem: I want bounding box just around hand so that I can crop it and do further operations but I am getting image as output in which there is bounding box around every object.

[Image Analyst]

Can you start your own thread so you'll get emails about updates instead of Felix?

[Explorer]

Sure

[Explorer]

Here it is http://www.mathworks.com/matlabcentral/answers/112917-how-to-detect-hand

[syhem samti]

does it work the same way as "vision.BlobAnalysis"? same results?

[Torkan]

Hi,

How can we define the length and width of these rectangles?

[DANIEL SYAFIQ]

THANK YOU SO MUCH IMAGE ANALYST.

Answer 2

[Tiago Almeida]

How can i draw the rectangles with the same size using this code?

labeledImage = bwlabel(A);
measurements = regionprops(labeledImage, 'BoundingBox', 'Area');
for k = 1 : length(measurements)
  thisBB = measurements(k).BoundingBox;
  rectangle('Position', [thisBB(1),thisBB(2),thisBB(3),thisBB(4)],...
  'EdgeColor','r','LineWidth',2 )
end

[Image Analyst]

Instead of having variable widths and heights, like this thisBB(3),thisBB(4), replace that with some fixed widths and heights.

rectangle('Position', [thisBB(1),thisBB(2), fixedWidth, fixedHeight],...
'EdgeColor','r','LineWidth',2 )

[Maham Khan]

how can we store/save the four values of bounding box for more than one images in a mat/text file calculated through following code

 for k = 1 : length(measurements)
  thisBB = measurements(k).BoundingBox;
  rectangle('Position', [thisBB(1),thisBB(2),thisBB(3),thisBB(4)],...
  'EdgeColor','r','LineWidth',2 )
 end

[Image Analyst]

Try this:

allBB = zeros(length(measurements), 4);
for k = 1 : length(measurements)
    thisBB = measurements(k).BoundingBox;
    rectangle('Position',  [thisBB(1),thisBB(2),thisBB(3),thisBB(4)],...
    'EdgeColor', 'r', 'LineWidth', 2)
    allBB(k, :) = thisBB;
end

[Maham Khan]

Thanks @Image Analyst

Answer 3

[Hafsa Asad]

Here is an even simpler way to do it if you have the binary image with white blobs

    st = regionprops(my_binary_image, 'BoundingBox', 'Area' );

    for ii= 1 : length(st)
        Areai(ii)= st(ii).Area;
    end
    largest_blob_id= find(Areai==max(Areai)); 
imshow(my_binary_image) 
rectangle('Position'[st(largest_blob_id).BoundingBox(1),st(largest_blob_id).BoundingBox(2),st(largest_blob_id).BoundingBox(3),st(largest_blob_id).BoundingBox(4)], 'EdgeColor','r','LineWidth',2 )

[Image Analyst]

That would be good if he wanted to draw the box around only the largest blob instead of drawing "N rectangles for N objects". An even shorter way would be to get rid of the for loop like this:

st = regionprops(my_binary_image, 'BoundingBox', 'Area' );
[maxArea, indexOfMax] = max([st.Area]);
rectangle('Position'[st(indexOfMax).BoundingBox(1),st(indexOfMax).BoundingBox(2),st(indexOfMax).BoundingBox(3),st(indexOfMax).BoundingBox(4)], 'EdgeColor','r','LineWidth',2 )

[Hafsa Asad]

Image Analyst, you are right. thanks.

Answer 4

[sidraa Aleem]

@Image Analyst I am trying to use the following code to do exactly what Felix wanted,but I am having error.

for k = 1 : length(st)
    thisBB = st(k).BoundingBox;
    rectangle('Position', [thisBB(1),thisBB(2),thisBB(3),thisBB(4)],...
    'EdgeColor','r','LineWidth',2 )
  end

Error using rectangle Value not a numeric scalar Please help me to resolve it.

Answer 5

[Masar Uthaib]

Hello

rectangle('Position',[st.BoundingBox(1),st.BoundingBox(2),st.BoundingBox(3),st.BoundingBox(4)],...
    'EdgeColor','r','LineWidth',2 )

does not operate with me. Can anyone clarify to me what is wrong?

[Image Analyst]

No one, except you, did that. This should work if you have a single blob:

rectangle('Position', st.BoundingBox, 'EdgeColor','r','LineWidth',2 )

If you have multiple blobs, try this:

measurements = regionprops(mask, 'BoundingBox');
allBB = vertcat(props.BoundingBox);
hold on;
for k = 1 : length(measurements)
    thisBB = measurements(k).BoundingBox; % Or allBB(k, :)
    rectangle('Position',  thisBB, 'EdgeColor', 'r', 'LineWidth', 2);
end
hold off;

Answer 6

[Muhammad Zulkifli]

How can i get bounding box ?

[Image Analyst]

It has been explained about how to use regionprops to get the bounding box of blobs in your binary image. In short:

props = regionprops(binaryImage, 'BoundingBox');
allBoundingBoxes = vertcat(props.BoundingBox)