[Bug]: Making an RGB image from pickled data throws error #28448
Description
Bug summary
Getting an error when saving an animated RGB image that was loaded from a pickled figure. I've isolated the error to matplotlib 3.9.0, with this code working in 3.8.3, which makes me think that this is to do with the pybind11 upgrade in #26275?
Things I've tried:
- Grayscale images (eg
data = np.random.rand(100, 100)) work. - Numpy v1.26.4 and v2.0.0 show no difference in behavior
- This shows up at least on WSL and Ubuntu
- In the debugger, both
data.dtypeandout.dtypeare showing'float64'prior to the_image.resamplecall.- However, if I re-cast the arrays with
data = data.astype('float64'),out = ..., then the_image.resamplecall no longer fails! - If I re-cast only one, then
out.dtype == data.dtypereturnsTrue, but on the function call I get the errorValueError: Input and output arrays have mismatched types - ... so something is up with the types, and the C++ code is bombing. But python is saying things line up.
- However, if I re-cast the arrays with
See these parts of the source:
matplotlib/lib/matplotlib/image.py
Lines 205 to 213 in d7d1bba
matplotlib/src/_image_wrapper.cpp
Lines 174 to 199 in d7d1bba
Code for reproduction
import io
import pickle
import numpy as np
import matplotlib.pyplot as plt
from pathlib import Path
from matplotlib.animation import FuncAnimation
dir = Path(__file__).parent.resolve()
# generate random rgb data
fig, ax = plt.subplots()
np.random.seed(0)
data = np.random.rand(100, 100, 3)
ax.imshow(data)
# pick the figure and reload
buf = io.BytesIO()
pickle.dump(fig, buf)
buf.seek(0)
fig_pickled = pickle.load(buf)
# Animate
def update(frame):
return ax,
ani = FuncAnimation(fig_pickled, update, frames=2)
# Save the animation
filepath = dir / 'test.gif'
ani.save(filepath)Actual outcome
Exception has occurred: ValueError
arrays must be of dtype byte, short, float32 or float64
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py", line 208, in _resample
_image.resample(data, out, transform,
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py", line 567, in _make_image
output = _resample( # resample rgb channels
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py", line 952, in make_image
return self._make_image(self._A, bbox, transformed_bbox, clip,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py", line 653, in draw
im, l, b, trans = self.make_image(
^^^^^^^^^^^^^^^^
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/artist.py", line 72, in draw_wrapper
return draw(artist, renderer)
^^^^^^^^^^^^^^^^^^^^^^
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py", line 132, in _draw_list_compositing_images
a.draw(renderer)
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/axes/_base.py", line 3110, in draw
mimage._draw_list_compositing_images(
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/artist.py", line 72, in draw_wrapper
return draw(artist, renderer)
^^^^^^^^^^^^^^^^^^^^^^
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py", line 132, in _draw_list_compositing_images
a.draw(renderer)
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/figure.py", line 3157, in draw
mimage._draw_list_compositing_images(
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/artist.py", line 72, in draw_wrapper
return draw(artist, renderer)
^^^^^^^^^^^^^^^^^^^^^^
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/artist.py", line 95, in draw_wrapper
result = draw(artist, renderer, *args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/backends/backend_agg.py", line 387, in draw
self.figure.draw(self.renderer)
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/backends/backend_agg.py", line 432, in print_raw
FigureCanvasAgg.draw(self)
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/backend_bases.py", line 2054, in <lambda>
print_method = functools.wraps(meth)(lambda *args, **kwargs: meth(
^^^^^
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/backend_bases.py", line 2204, in print_figure
result = print_method(
^^^^^^^^^^^^^
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/backends/backend_qtagg.py", line 75, in print_figure
super().print_figure(*args, **kwargs)
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/figure.py", line 3390, in savefig
self.canvas.print_figure(fname, **kwargs)
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/animation.py", line 371, in grab_frame
self.fig.savefig(self._proc.stdin, format=self.frame_format,
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/animation.py", line 1109, in save
writer.grab_frame(**savefig_kwargs)
File "/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/_test_pybind11_error.py", line 35, in <module>
ani.save(filepath)
ValueError: arrays must be of dtype byte, short, float32 or float64
Matplotlib Version
3.9.0