On Sat, 13 Dec 2014 16:53:06 +0100 "Nicolas P. Rougier" Nicolas.Rougier@inria.fr wrote:
Does anyone has a simple 2D linear interpolation for resizing an image (without scipy) ?
Ideally, something like ```def zoom(Z, ratio): ...``` where Z is a 2D scalar array and ratio the scaling factor. (I'm currently using ```scipy.ndimage.interpolation.zoom``` but I would like to avoid the scipy dependency)
I have a self-contained cython class for that: https://github.com/kif/pyFAI/blob/master/src/bilinear.pyx
The formula for bilinear interpolation in implemented there but it needs some additionnal work for what you want to do.
Beside this I implemented an antialiased downscaler using Lanczos (order 1, 2 or 3) https://github.com/kif/imagizer/blob/qt/src/down_sampler.pyx.
Create a downscaler: ds = down_sampler.DownScaler() scaled_img = ds.scale(img, 4.5)
In this case the interpolation will be done on a vinicy of (2*4.5*3+1) pixel in the input image (and 2*3+1 in the output image) as it is doing Lanczos 3 by default. This implementation is 2x faster than the Antialiased downscaler in PIL.