MATLAB: How to recognize the number

image processingImage Processing Toolbox

Hi everyone, I'm doing a project to recognize the speed limit traffic sign. I have a image like this:

http://nr0.upanh.com/b3.s33.d1/9d1e97d87c03b41f01e1693c726a410e_50164610.1.jpg

how to make it become like this picture:

http://nr5.upanh.com/b6.s33.d3/4ae3137747cb7510ea9723cf3b1cac17_50148075.2.jpg

My problem is: how to mark pixels at the border between object and background like in above image.

Can you help me? thanks in advance!

Best Answer

I don't know what pixels you're talking about. If you want all the pixels on the object's perimeter, you can use bwperim() or bwboundaries(). If you want the bounding box, you can use regionprops. If you want those "c" points, you're going to have to extract those lines from the image and use find().

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What is there to not understand?

The code uses logical indexing to set the pixels of the perimeter to 255 in the grayscale image.

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What if the blob is shaped like a C or a G? Is that roughly circular? If so, you'll need to call bwconvhull() first. If not, you can look at the ration of perimeters square to areas

measurements = regionprops(binaryImage, 'Area', 'Perimeter');
allAreas = [measurements.Area];
allPerimeters = [measurements.Perimeter];
circularities = 4*pi*allAreas ./ allPerimeters^2;

round objects will have circularity values more than around 0.8 or so, or whatever value you want to go with.

Best Answer

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