OpenCV Q&A Forum - RSS feedhttp://answers.opencv.org/questions/OpenCV answersenCopyright <a href="http://www.opencv.org">OpenCV foundation</a>, 2012-2018.Wed, 24 Apr 2013 15:45:44 -0500How to find whether an image is blurry or not using fft ?http://answers.opencv.org/question/11910/how-to-find-whether-an-image-is-blurry-or-not-using-fft/How do I find out whether an image has been blurred using fft?Thu, 18 Apr 2013 13:59:17 -0500http://answers.opencv.org/question/11910/how-to-find-whether-an-image-is-blurry-or-not-using-fft/Answer by zerog80 for <p>How do I find out whether an image has been blurred using fft?</p>
http://answers.opencv.org/question/11910/how-to-find-whether-an-image-is-blurry-or-not-using-fft/?answer=12320#post-id-12320FFT works in *frequency domain*, blurriness is a *spatial characteristic* and it's better if you approximate it with the magnitude of horizontal and vertical derivatives as explained [here](http://answers.opencv.org/question/5395/calculate-blurness-and-sharpness-of-a-given-image/).Wed, 24 Apr 2013 09:48:59 -0500http://answers.opencv.org/question/11910/how-to-find-whether-an-image-is-blurry-or-not-using-fft/?answer=12320#post-id-12320Comment by Guanta for <p>FFT works in <em>frequency domain</em>, blurriness is a <em>spatial characteristic</em> and it's better if you approximate it with the magnitude of horizontal and vertical derivatives as explained <a href="http://answers.opencv.org/question/5395/calculate-blurness-and-sharpness-of-a-given-image/">here</a>.</p>
http://answers.opencv.org/question/11910/how-to-find-whether-an-image-is-blurry-or-not-using-fft/?comment=12324#post-id-12324Why should blurriness be a spatial characteristic? E.g. a simple Gauss-filter changes the frequency of the image (low pass filter). And of course blurriness can be computed in the frequency domain, see e.g. one of the first google hits: http://www.filiprooms.be/publications/accvpap.pdf .Wed, 24 Apr 2013 10:20:26 -0500http://answers.opencv.org/question/11910/how-to-find-whether-an-image-is-blurry-or-not-using-fft/?comment=12324#post-id-12324Answer by unxnut for <p>How do I find out whether an image has been blurred using fft?</p>
http://answers.opencv.org/question/11910/how-to-find-whether-an-image-is-blurry-or-not-using-fft/?answer=12333#post-id-12333If you have the original image available, you can compute the distribution of frequencies in both the original and "blurred" image. If the image has indeed been blurred, you will have fewer high frequency components.Wed, 24 Apr 2013 15:45:44 -0500http://answers.opencv.org/question/11910/how-to-find-whether-an-image-is-blurry-or-not-using-fft/?answer=12333#post-id-12333