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POimage focus and FFT
 

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    <p>I am a new to Matlab and I have a project that involves image processing.</p> <p>I have a number of RGB images and I need to find a way to separate the out of focus from the in focus images. I do not need to correct the focus of the out of focus ones, I just need to find which are out of focus and remove them. I have done <code>FFT2</code> to the image and then used the radial average of the image of the power spectrum to see if there is a difference between the in focus or out of focus but I do not see a difference between the two.</p> <p>I decided to use the gradient of the image </p> <pre><code>[gradx,grady]=gradient(image) </code></pre> <p>and then take the magnitude </p> <pre><code>new_image=sqrt((gradx.^2)+(grady.^2)) </code></pre> <p>and try to do the <code>FFT2</code> using the <code>new_image</code> now instead of the <code>image</code>. The power spectrum does not look like what I expect so I am not sure if I should do the <code>FFT2</code> on the <code>new_image</code> of the <code>gradx</code> and <code>grady</code> separately. Has anyone have any thoughts about whether this is the right way to do this?</p> <p>I was also thinking that instead of using the gradient to use a Sobel mask</p> <pre><code>mask=fspecial('sobel') mask_x=imfilter(image,mask) mask_y=imfilter(image,mask') new_image=sqrt((mask_x.^2)+(mask_y.^2)) </code></pre> <p>and then do <code>FFT2</code> in the <code>new_image</code> but again the power spectrum is not right. I expect it to start from zero and instead it starts from the highest value and drops exponentially.</p> <p>Has anyone tried to classify images using this method? Thank you for reading.</p>
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    1. COIt's hard to visualize exactly what you mean by "the power spectrum is not right. I expect it to start from zero and instead it starts from the highest value and drops exponentially." But it suggests to me that you may be omitting to call FFTSHIFT before inspecting the results.
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    2. CO`fftshift` your spectrum!!
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    3. COSorry for the confusion, I left out that I was already using the FFTSHIFT.
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