Drawing a boundary box around an image?

Question

Warid Islam 2022-9-29

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1814260-drawing-a-boundary-box-around-an-image

评论： Warid Islam 2022-9-30

bb.png

I want to draw a boundary box around an image. I tried the code below, but it is throwing me an error. Any suggestions would be appreciated.

m=imread('bb.png')
props = regionprops(m, 'BoundingBox');
bbx = rectangle('Position',props.BoundingBox,'EdgeColor','b','LineWidth',3);

I am getting the following error message.

Error using rectangle

Input arguments must be parameter-value pairs. Each parameter name must be followed by a corresponding value.

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KSSV 2022-9-29

props is a structire....you cannot use that like you have used. What exactly you want to do?

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Answer 1

Walter Roberson 2022-9-29

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1814260-drawing-a-boundary-box-around-an-image#answer_1063635

在 MATLAB Online 中打开

My goal is to create a bounding box around the non-zero pixel value region of my image.

filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/1140570/box.png';

I = imread(filename);

BW = imbinarize(I);

hmask = any(BW,1);

vmask = any(BW,2);

firstrow = find(hmask, 1); lastrow = find(hmask, 1, 'last');

firstcol = find(vmask, 1); lastcol = find(vmask, 1, 'last');

imshow(I);

rectangle('Position', [firstrow, firstcol, lastrow-firstrow, lastcol-firstcol], 'EdgeColor', 'r');

What happened? Well... it turns out that your image has a white border around it. White borders are non-zero so the entire image needs to be enclosed in the border according to your stated requirements.

BW = any(I < 240, 3) & any(I > 10,3);

hmask = any(BW,1);

vmask = any(BW,2);

firstrow = find(hmask, 1); lastrow = find(hmask, 1, 'last');

firstcol = find(vmask, 1); lastcol = find(vmask, 1, 'last');

imshow(I);

rectangle('Position', [firstrow, firstcol, lastrow-firstrow, lastcol-firstcol], 'EdgeColor', 'r');

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Warid Islam 2022-9-30

Hi @Walter Roberson,

Thank you very much.

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Answer 2

KSSV 2022-9-29

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1814260-drawing-a-boundary-box-around-an-image#answer_1062970

在 MATLAB Online 中打开

I = imread('https://in.mathworks.com/matlabcentral/answers/uploaded_files/1139790/bb.png');

props = regionprops(rgb2gray(I), 'BoundingBox');

imshow(I)

hold on

for i = 1:length(props)

rectangle('Position',props(i).BoundingBox,'EdgeColor','b','LineWidth',3);

end

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Warid Islam 2022-9-29

Hi @KSSV,

Thank you for your response. I don't get any error message. However, after using imcrop, the size of my image reduces which may not be the ideal case. I am using images of the same size which I would multiply later. If the above image size decreases, then the later operations would give me an error message. My goal is to create a bounding box around the non-zero pixel value region of my image.I would perform some algorithm later on which I would like to restrict within the bounding box. I was wondering if it is possible to create a bounding box without reducing the size of the image.

Warid Islam 2022-9-29

在 MATLAB Online 中打开

box.png

Hi @KSSV,

I tried to implement your code above.

I = imread('https://in.mathworks.com/matlabcentral/answers/uploaded_files/1139790/bb.png');
props = regionprops(rgb2gray(I), 'BoundingBox');
imshow(I)
hold on
for i = 1:length(props)
    rectangle('Position',props(i).BoundingBox,'EdgeColor','b','LineWidth',3);
end

The region inside the box is filled with Blue color. I just want the boundary to be Blue and the inside region remain visible to me. I would implement some algorithms later which would be limited inside the box.

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