regionprops Bounding box property returns values outside image dimensions

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Hi,
I am using Matlab R2022a. I am trying to draw bounding boxes to an image considering English alphabets. I am extremely new to Matlab so I apologize if my question or technique is wrong.
I considered using thresholding after binarizing the image and then using connected components to find the bounding boxes. Here is my code:
image = imread(image_path);
image = im2double(imcomplement(image));
image1 = imbinarize(image_comp);
connected = bwconncomp(image1);
imshow(image1);
props = regionprops(connected, 'BoundingBox');
for i = 1:connected.NumObjects
if(props(i).BoundingBox(1) > connected.ImageSize(1))
rectangle('Position', props(i).BoundingBox,'EdgeColor', [0, 1, 0], 'LineWidth', 2)
continue;
end
rectangle('Position', props(i).BoundingBox,'EdgeColor', [1, 0, 0], 'LineWidth', 2)
end
I noticed that some of the x values in the bounding boxes returned were outside the dimensions of the actual image (drawn in green colour). So I am unable to crop these regions of the image.
Here is the output I receive:
Please advice on what I am doing wrong.
  1 件のコメント
Image Analyst
Image Analyst 2022 年 9 月 21 日
Not sure what you mean. All boxes, red or green, completely contain one blob. None of the bounding box x values of the left edge should be outside the image (below a value of 1).
props = regionprops(connected, 'BoundingBox');
boundingBoxes = vertcat(props.BoundingBox); % List of [xLeft, yTop, width, height] values. Each row is a different blob.

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採用された回答

Image Analyst
Image Analyst 2022 年 9 月 22 日
Moved: Image Analyst 2022 年 9 月 23 日
OK @sarvan_keep you haven't answered either of us so I guess you must be having great difficulty. So attached is a full demo that identifies the letters, put boxes around them, and also crops out the bounding boxes into new sub images. You can then process each sub image (like do OCR on it) or save it to disk, whatever you want.
Another thing left to do is to merge bounding boxes of small blobs, like dots above the i, into the nearest other box. But I'm sure you can do that. There is a variety of ways to do that.
Please respond.
  5 件のコメント
sarvan_keep
sarvan_keep 2022 年 9 月 25 日
Thank you so much.

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その他の回答 (1 件)

Matt J
Matt J 2022 年 9 月 21 日
編集済み: Matt J 2022 年 9 月 21 日
You should be comparing BoundingBox(1) with ImageSize(2)
image = imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1132160/image.jpeg');
image_comp = im2gray(imcomplement(image));
image1 = imbinarize(image_comp);
connected = bwconncomp(image1);
imshow(image1);
props = regionprops(connected, 'BoundingBox');
for i = 1:connected.NumObjects
if(props(i).BoundingBox(1) > connected.ImageSize(2))
rectangle('Position', props(i).BoundingBox,'EdgeColor', [0, 1, 0], 'LineWidth', 2)
continue;
end
rectangle('Position', props(i).BoundingBox,'EdgeColor', [1, 0, 0], 'LineWidth', 2)
end
  3 件のコメント
Matt J
Matt J 2022 年 9 月 23 日
You're welcome, but please Accept-click the answer to indicate that it addressed your question.

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