MATLAB: What is the difference between bilinear image resizing and averaged downsampling

image analysis

I note imresize has the method option 'bilinear'. Does this method have the same effect as averaged downsampling? For example, given an image A, imresize(A,0.5,'bilinear'), is this equivalent to 2*2 averaged binning? How is the bilinear resizing implemented by Matlab?

Best Answer

I would suggest you refer imresize which states that "Bilinear interpolation; the output pixel value is a weighted average of pixels in the nearest 2-by-2 neighborhood".

You may also refer to interpolation methods for further details about implementation.

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MATLAB: Help with Cubic spline interpolation

You can use interp2 with the 'spline' input option. You could also use griddedInterpolant in a similar way, and that would be better if you're going to be doing interpolations of the same image multiple times.

MATLAB: Downsampling image

Hi, You can use dyaddown() from the Wavelet Toolbox.

    x = randn(8,8);
    % this gives you 1st row, 1st column, 3rd row, 3rd colum, etc
    y = dyaddown(x,'m',1);
    % now this gives you 2nd row, 2nd column, etc
    y = dyaddown(x,'m',0);

Or you can use downsample() from the Signal Processing Toolbox. This gives you one polyphase matrix.

     Y = downsample(x,2,0);
     Y = (downsample(Y',2,0))';

This gives you the other:

       Y1 = downsample(x,2,1);
       Y1 = (downsample(Y1',2,1))';

Hope that helps,

Wayne

Best Answer

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MATLAB: Downsampling image

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