spot red object in a image

Question

Emmanuel 2014-5-13

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https://ww2.mathworks.cn/matlabcentral/answers/129439-spot-red-object-in-a-image

回答： Image Analyst 2014-5-13

Hello!

Can You please tell me as to how to spot red markers in an image. here is my code:

I = imread('pic', 'png'),
data = imsubtract((:,:,1) , rgb2gray(I));

I am getting an array cause image is a 2D array. How do I change this code?

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Walter Roberson 2014-5-13

What were you hoping for instead of an array ?

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Answer 1

Image Analyst 2014-5-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/129439-spot-red-object-in-a-image#answer_136652

Your first argument to imsubtract is nonsense. It's not even an image, it's just (:,:,1). I'm surprised it didn't throw an error. Even if it were an image, subtracting it from the gray scale version of the image will not be very good or robust except for high contrast images.

See my color segmentation demos: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862

That's from the Delta E method where I found red, but you'll probably want to use the HSV method: http://www.mathworks.com/matlabcentral/fileexchange/28512-simple-color-detection-by-hue