René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Making an RGB image from pickled data throws error","articleBody":"### Bug summary\r\n\r\nGetting 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 https://github.com/matplotlib/matplotlib/pull/26275?\r\n\r\nThings I've tried:\r\n* Grayscale images (eg `data = np.random.rand(100, 100)`) work.\r\n* Numpy v1.26.4 and v2.0.0 show no difference in behavior\r\n* This shows up at least on WSL and Ubuntu  \r\n* In the debugger, both `data.dtype` and `out.dtype` are showing `'float64'` prior to the `_image.resample` call.\r\n    * However, if I re-cast the arrays with `data = data.astype('float64')`, `out = ...`, then the `_image.resample` call no longer fails! \r\n     * If I re-cast only one, then `out.dtype == data.dtype` returns `True`, but on the function call I get the error `ValueError: Input and output arrays have mismatched types`\r\n     * ... so something is up with the types, and the C++ code is bombing. But python is saying things line up.\r\n\r\n\r\nSee these parts of the source: \r\n\r\nhttps://github.com/matplotlib/matplotlib/blob/d7d1bba818ef36b2475b5d73cad6394841710211/lib/matplotlib/image.py#L205-L213\r\nhttps://github.com/matplotlib/matplotlib/blob/d7d1bba818ef36b2475b5d73cad6394841710211/src/_image_wrapper.cpp#L174-L199\r\n\r\n\r\n### Code for reproduction\r\n\r\n```Python\r\nimport io\r\nimport pickle\r\nimport numpy as np\r\nimport matplotlib.pyplot as plt\r\nfrom pathlib import Path\r\nfrom matplotlib.animation import FuncAnimation\r\n\r\ndir = Path(__file__).parent.resolve()\r\n\r\n# generate random rgb data\r\nfig, ax = plt.subplots()\r\nnp.random.seed(0)\r\ndata = np.random.rand(100, 100, 3)\r\nax.imshow(data)\r\n\r\n# pick the figure and reload\r\nbuf = io.BytesIO()\r\npickle.dump(fig, buf)\r\nbuf.seek(0)\r\nfig_pickled = pickle.load(buf)\r\n\r\n# Animate\r\ndef update(frame):\r\n    return ax,\r\n\r\nani = FuncAnimation(fig_pickled, update, frames=2)\r\n\r\n# Save the animation\r\nfilepath = dir / 'test.gif' \r\nani.save(filepath)\r\n```\r\n\r\n\r\n### Actual outcome\r\n\r\n```\r\nException has occurred: ValueError\r\narrays must be of dtype byte, short, float32 or float64\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py\", line 208, in _resample\r\n    _image.resample(data, out, transform,\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py\", line 567, in _make_image\r\n    output = _resample(  # resample rgb channels\r\n             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py\", line 952, in make_image\r\n    return self._make_image(self._A, bbox, transformed_bbox, clip,\r\n           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py\", line 653, in draw\r\n    im, l, b, trans = self.make_image(\r\n                      ^^^^^^^^^^^^^^^^\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/artist.py\", line 72, in draw_wrapper\r\n    return draw(artist, renderer)\r\n           ^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py\", line 132, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/axes/_base.py\", line 3110, in draw\r\n    mimage._draw_list_compositing_images(\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/artist.py\", line 72, in draw_wrapper\r\n    return draw(artist, renderer)\r\n           ^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/image.py\", line 132, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/figure.py\", line 3157, in draw\r\n    mimage._draw_list_compositing_images(\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/artist.py\", line 72, in draw_wrapper\r\n    return draw(artist, renderer)\r\n           ^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/artist.py\", line 95, in draw_wrapper\r\n    result = draw(artist, renderer, *args, **kwargs)\r\n             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/backends/backend_agg.py\", line 387, in draw\r\n    self.figure.draw(self.renderer)\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/backends/backend_agg.py\", line 432, in print_raw\r\n    FigureCanvasAgg.draw(self)\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/backend_bases.py\", line 2054, in \u003clambda\u003e\r\n    print_method = functools.wraps(meth)(lambda *args, **kwargs: meth(\r\n                                                                 ^^^^^\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/backend_bases.py\", line 2204, in print_figure\r\n    result = print_method(\r\n             ^^^^^^^^^^^^^\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/backends/backend_qtagg.py\", line 75, in print_figure\r\n    super().print_figure(*args, **kwargs)\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/figure.py\", line 3390, in savefig\r\n    self.canvas.print_figure(fname, **kwargs)\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/animation.py\", line 371, in grab_frame\r\n    self.fig.savefig(self._proc.stdin, format=self.frame_format,\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/lib/matplotlib/animation.py\", line 1109, in save\r\n    writer.grab_frame(**savefig_kwargs)\r\n  File \"/mnt/c/Users/Scott/Documents/Documents/Coding/matplotlib/_test_pybind11_error.py\", line 35, in \u003cmodule\u003e\r\n    ani.save(filepath)\r\nValueError: arrays must be of dtype byte, short, float32 or float64\r\n```\r\n\r\n### Matplotlib Version\r\n\r\n3.9.0","author":{"url":"https://github.com/scottshambaugh","@type":"Person","name":"scottshambaugh"},"datePublished":"2024-06-24T16:33:04.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/28448/matplotlib/issues/28448"}