Efficient Background subtraction with OpenCV

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I want to do background subtraction in a video file using OpenCV method. Right now I'm able to do background subtraction, but the problem is that I couldn't get the output in color mode. All the output after subtracting the background is coming in grayscale color mode :(. I want to get the color information to the foreground which is the resulting output after background got subtracted.

Can I do it using masking technique?? like the following procedure which I'm thinking about.

Capture Input -- InputFrame (RGB)
Process InputFrame
Subtract background, store foreground in TempFrame (which is coming in grayscale :( )
Create a mask using TempFrame
Apply the created mask to the InputFrame
Get colored foreground as OutFrame

I'm struck up with doing the masking using OpenCV. I'm just a very beginner in OpenCV. Please help me to overcome this.

Thanks in advance.

Measurement answered 8/1, 2010 at 9:59 Comment(0)

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Okay, I don't understand how TempFrame (your foreground) could be greyscale if you are using background subtraction. You must be using a very special algorithm. But assuming TempFrame is greyscale, then you would do this:

cv::Mat mask = tempFrame > 0.5;

cv::Mat outFrame;
capturedFrame.copyTo(outFrame, mask);

That is OpenCV 2.0 code above. The number 0.5 is a threshold, you'll need to set it to something appropriate. If you're not using floating-point images, you'd probably set it to 128 or something like that. This is the same thing in OpenCV 1.1 code:

CvMat* mask = cvCreateMat(tempFrame.rows, tempFrame.cols, CV_8UC1);
cvCmpS(tempFrame, 0.5, mask);

CvMat* outFrame = cvCreateMat(capturedFrame.rows, capturedFrames.cols, CV_32FC3);
cvCopy(capturedFrame, outFrame, mask);

Pottle answered 17/1, 2010 at 11:2 Comment(2)

Thank you, But i still wonder why all the examples and code for BGS i come across the internet generate only Grayscale output? Anyways.. Thanks again. – Measurement 19/1, 2010 at 6:59

Oh okay, I suppose it's just easier to do background subtraction with greyscale so maybe that's why. – Pottle 19/1, 2010 at 9:34

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http://vimeo.com/27477093

code is here

http://code.google.com/p/derin-deli-mavi/downloads/detail?name=denemeOpenCv23.zip&can=2&q=

to reach a colored foreground just copy image by using foreground mask

// image.copyTo(foreground,foreground);

Appease answered 14/8, 2011 at 22:45 Comment(0)

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Okay, I don't understand how TempFrame (your foreground) could be greyscale if you are using background subtraction. You must be using a very special algorithm. But assuming TempFrame is greyscale, then you would do this:

cv::Mat mask = tempFrame > 0.5;

cv::Mat outFrame;
capturedFrame.copyTo(outFrame, mask);

That is OpenCV 2.0 code above. The number 0.5 is a threshold, you'll need to set it to something appropriate. If you're not using floating-point images, you'd probably set it to 128 or something like that. This is the same thing in OpenCV 1.1 code:

CvMat* mask = cvCreateMat(tempFrame.rows, tempFrame.cols, CV_8UC1);
cvCmpS(tempFrame, 0.5, mask);

CvMat* outFrame = cvCreateMat(capturedFrame.rows, capturedFrames.cols, CV_32FC3);
cvCopy(capturedFrame, outFrame, mask);

Pottle answered 17/1, 2010 at 11:2 Comment(2)

Thank you, But i still wonder why all the examples and code for BGS i come across the internet generate only Grayscale output? Anyways.. Thanks again. – Measurement 19/1, 2010 at 6:59

Oh okay, I suppose it's just easier to do background subtraction with greyscale so maybe that's why. – Pottle 19/1, 2010 at 9:34

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