How to know the size and the pixel coordinates when drawing a bounding box on an image

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Nalini 2016-11-15

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https://ww2.mathworks.cn/matlabcentral/answers/312415-how-to-know-the-size-and-the-pixel-coordinates-when-drawing-a-bounding-box-on-an-image

回答： Image Analyst 2016-11-15

采纳的回答： Image Analyst

I am drawing bounding boxes on objects which are far and close to the camera in an image.
Object close to camera is larger in size and object farther from camera is smaller in size.
I will then train an object detector using these ground truthed data as positive data.
How can know the pixel coordinates and the size of a bounding box so i can train the detector differently for objects closer (larger bounding box) and farther from camera (smaller bounding box).

Thanks a lot!

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Answer 1

Image Analyst 2016-11-15

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The pixel coordinates and width and height of the bounding box(es) are returned from regionprops(). First you segment your objects to get a binary image of where your objects are, then label your binary image and send it in to regionprops() asking for the bounding box.

labeledImage = bwlabel(binaryImage);
props = regionprops(labeledImage, 'BoundingBox');

props is a structure array. Each structure in the array has a field called Bounding Box that contains an array, [leftColumn, topRow, width, height], with units of pixels.

See my Image Segmentation Tutorial for a full demo. http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862