Get interpolated data from imshow

Question

I use matpotlib's imshow() to interpolate and plot some data. Here is a 2D array.

im = ax.imshow(data2D,interpolation='sinc')

I would like to get the 'sinc' interpolated data after imshow. I haven't been able to find any method to do so. Any idea? Thanks, Nicolas

The data is the image itself. I don't think it's available outside the rendering context. But maybe you would rather apply some filter to the data before plotting it? — ImportanceOfBeingErnest, Sep 20 '18 at 10:47
I know but I couldn't find an equivalent method to get the 'sinc' 2D interpolation. — Begbi, Sep 26 '18 at 02:30
Does this work? https://numpy.org/doc/stable/reference/generated/numpy.sinc.html — smerkd, Oct 09 '21 at 13:58

score 0 · Answer 1 · answered Nov 04 '21 at 16:26

0

The matplotlib C++ resampling code is interfaced in the matplotlib.image.resample function, which you can import and call on your own.

answered Nov 04 '21 at 16:26

Yannick Copin

76
9

Please give an example of using this method to interpolate an array. Currently it is unclear how the function should be utilized. – Lupilum May 05 '23 at 14:01

score 0 · Answer 2 · answered May 06 '23 at 09:59

As an addendum to Yannick Copin's answer which reads

The matplotlib C++ resampling code is interfaced in the matplotlib.image.resample function, which you can import and call on your own.

Here is a visual demo of interpolation using the private function matplotlib.image._resample

import matplotlib.pyplot as plt
import numpy as np
from matplotlib.image import _resample
from matplotlib.transforms import Affine2D

np.random.seed(19680801)

grid = np.random.rand(4, 4)
scale_factor = 10
out_dimensions = (grid.shape[0]*scale_factor, grid.shape[1]*scale_factor)

fig, axs = plt.subplots(nrows=3)

transform = Affine2D().scale(scale_factor, scale_factor)
# Have to get an image to be able to resample
# Resample takes an _ImageBase or subclass, which require an Axes
img = axs[0].imshow(grid, interpolation='spline36', cmap='viridis')
interpolated = _resample(img, grid, out_dimensions, transform=transform)

axs[0].imshow(grid, cmap='viridis')
axs[1].imshow(grid, interpolation='spline36', cmap='viridis')
axs[2].imshow(interpolated, cmap='viridis')

Get interpolated data from imshow

2 Answers2