Sequel of a Specified Region

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Tricky 2011-10-28

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https://ww2.mathworks.cn/matlabcentral/answers/19686-sequel-of-a-specified-region

sorry ImageAnalyst...

Unfortunately I deleted a question answered by ImageAnalyst and accepted by Me.

ImageAnalyst after doing filtering for particular portion is it possible to apply Fourier transform for that portion only to extract frequencies.

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Image Analyst 2011-10-28

Par for the course. Not only do accepted (or unaccepted) questions I've answered get deleted, but it's been noted that sometimes people accept worse or wrong answers in preference to my better or "right" answers. I'm sure it happens to others also. You weren't the first and you won't be the last.

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Image Analyst 2011-10-28

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Yes, of course. You should know however that since your "infinite" image is multiplied by a mask (whatever region zeros out and crops stuff out) your spectrum will be convolved with the FT of the mask shape. Recall that multiplication in the spatial domain corresponds to convolution in the spectral domain.

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Tricky 2011-10-30

Thanks for the Information.....

But In your *Demo Of Filtering a particular portion of Image* I created the binary image by cropping the image in a polygon shape instead of selecting it with mouse as your code does because the polygon selected region contains EDGES so I thought to do highpass filtering for that portion and finally extracting frequencies of that region.

here vertex_x and vertex_y are coordinates of that polygon in binaryimage.

Please explain something about how to extract frequencies in the frequency domain image(FT) by multiplying by a mask.

Thanks In Advance

Image Analyst 2011-10-30

Yes, but the high pass filtered image was on the original image. I didn't crop it like you did. When you did that, your polygon now fell outside of your new cropped region, unless you take care to subtract an offset from your polygon coordinates. So do that subtraction and then your polygon will now lie over your cropped image, and you can do the masking. Then take the FT and you'll have it. I'd have all the images be single or double so you don't have any problems due to integer quantization.

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