Scale up an image without interpolation

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Valentin Magidson
评论： Patryk Trybalski 2021-6-7
I have 3D image, which I need to scale up with integer scaling coefficient (e.g. x3, x5). ImageJ have an interpolation option "None", alongside with "Bilinear" and "Bicubic", but Matlab functions (like resize, imresize) do not include "none" option. It is useful for overlaying high resolution image over original low resolution one. I need to replace each voxel with a volume of identical value pixels. Can I do something smarter then nested FOR loops?

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采纳的回答

Image Analyst
Image Analyst 2016-1-6
The option is not called 'none', it's called 'nearest'. This will basically replicate voxels, not interpolate them. I'm sure your ImageJ is doing it the same way.
bigArray = imresize(smallArray, 3.456, 'nearest');
  2 个评论
Valentin Magidson
Valentin Magidson 2016-1-6
Thanks, it works great for 2D images. For 3D it operates on each 2D slice separately, but repmat(Matrix2D,1,1,scale) can expand each slice.
Patryk Trybalski
Patryk Trybalski 2021-6-7
Ain't 'nearset' the nearest neightbor interpolation?

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更多回答（1 个）

Adam
Adam 2016-1-6
编辑：Adam 2016-1-6
Something like this should work I think, with a single for loop. I'm not sure if it could be done without a for loop at all. Probably some combination of repmat and reshape may work to do the whole thing at once rather than a row at a time.
scaleFactor = 3;
inputImage = rand( 3, 4 );
outputImage = zeros( size( inputImage ) * scaleFactor );
nOutputColumns = size( outputImage, 2 );
outputRowIndices = 1:scaleFactor:size( outputImage, 1 );
for i = 1:size( inputImage, 1 )
idx = outputRowIndices(i);
outputImage( idx:idx+2, : ) = reshape( repmat( inputImage(i,:), scaleFactor^2 , 1 ), scaleFactor, nOutputColumns );
end

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