interpolation done without imresize

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P
P 2013-1-24
How to do nearest neighbor interpolation and bilinear interpolation on a gray scale image without using imresize? The code is supposed to mimic the operation of imresize but should not use any functions available on matlab.
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Matt J
Matt J 2013-1-24
should not use any functions available on matlab
I don't see how you're going to do nearest neighbor interpolation without MATLAB's round() function. You might want to clarify the scope of that restriction.
P
P 2013-1-24
You are right. There is no way to do nearest without round(). The objective is to stay away from imresize, interp where you can enter the method as nearest, bilinear and get the answer. other functions are permissible.

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Image Analyst
Image Analyst 2013-1-24
You can find the formulas here: http://en.wikipedia.org/wiki/Bilinear_interpolation
You'll have to scan your output image, figure out where the input pixel lies on your input pixel - it will be located somewhere in a square between 3 original input pixels. Then use the bilinear interpolation formula on Wikipedia to get the output pixel value. You can use a pair of for loops for this - one over rows and one over columns.
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P
P 2013-1-24
frow=min(round(((1:fscale(1))-1)./fs(1)+1),fim(1)); fcol=min(round(((1:fscale(2))-1)./fs(2)+1),fim(2));
this what I used for nearest neighbor but I am having difficulty in figuring out what should replace frow and fcol for bilinear.
Image Analyst
Image Analyst 2013-1-24
The formula for weighting the value according to how close it is to the different corners is in Wikipedia.

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Sean de Wolski
Sean de Wolski 2013-1-24
I would use interp2 or griddedInterpolant.
doc interp2
doc griddedInterpolant
  2 个评论
Image Analyst
Image Analyst 2013-1-24
"should not use any functions available on matlab."
Sean de Wolski
Sean de Wolski 2013-1-24
Well technically griddedInterpolant is a class with methods ;)

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