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Update image tutorial. by anntzer · Pull Request #23889 · matplotlib/matplotlib · GitHub

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Update image tutorial. - #23889

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timhoffm merged 1 commit into
matplotlib:mainfrom
anntzer:imtut
Sep 15, 2022
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Update image tutorial.#23889
timhoffm merged 1 commit into
matplotlib:mainfrom
anntzer:imtut

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anntzer commented Sep 14, 2022

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  • Use Pillow to load the image rather than the discouraged plt.imread.
  • Remove discussion about rescaling to 0-1 as dropping the use of plt.imread also gets rid of that (not so nice) behavior. Also drop the lengthy discussion about uint8 and float32, which seems out of place here (if anything it should be in the Pillow docs). Make corresponding fixes to code to use 0-255 instead of 0-1.
  • Fix subplot management to go full pyplot (the local switch to OO-style is a bit weird).
  • Fix interpolation discussion as the default is now "nearest" (actually it's now "antialiased", but let's sweep that under the rug for this tutorial for now).

See #22790. Probably the tutorial could be further improved, but let's consider this a small step in that direction.

PR Summary

PR Checklist

Tests and Styling

  • Has pytest style unit tests (and pytest passes).
  • Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

  • New features are documented, with examples if plot related.
  • New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
  • API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
  • Documentation is sphinx and numpydoc compliant (the docs should build without error).

story645 reviewed Sep 14, 2022
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Comment thread tutorials/introductory/images.py Outdated
Comment on lines +82 to +84
# Here, we used Pillow to open an image (with `PIL.Image.open`), and
# immediately converted the `PIL.Image.Image` object into a 8-bit
# (``dtype=uint8``) numpy array.

story645 Sep 14, 2022

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality
Suggested change
# Here, we used Pillow to open an image (with `PIL.Image.open`), and
# immediately converted the `PIL.Image.Image` object into a 8-bit
# (``dtype=uint8``) numpy array.
# We use Pillow to open an image (with `PIL.Image.open`), and
# immediately convert the `PIL.Image.Image` object into an 8-bit
# (``dtype=uint8``) numpy array.

And this should maybe be before the code instead of and here we go

Comment thread tutorials/introductory/images.py Outdated
@@ -205,20 +199,19 @@
#
# You can specify the clim in the call to ``plot``.

story645 Sep 14, 2022

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# You can specify the clim in the call to ``plot``.
# You can specify the clim (colormap limits) in the call to ``plot``.

I think clim is colormap limits?

Comment thread tutorials/introductory/images.py Outdated
Comment on lines +213 to +214
ax = fig.add_subplot(1, 2, 1)
plt.subplot(1, 2, 1)
imgplot = plt.imshow(lum_img)
ax.set_title('Before')
plt.colorbar(ticks=[0.1, 0.3, 0.5, 0.7], orientation='horizontal')
ax = fig.add_subplot(1, 2, 2)
plt.title('Before')
plt.colorbar(orientation='horizontal')
plt.subplot(1, 2, 2)
imgplot = plt.imshow(lum_img)
imgplot.set_clim(0.0, 0.7)
ax.set_title('After')
plt.colorbar(ticks=[0.1, 0.3, 0.5, 0.7], orientation='horizontal')
imgplot.set_clim(0, 175)
plt.title('After')
plt.colorbar(orientation='horizontal')

story645 Sep 14, 2022

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I think this should stay OO since that's what we usually recommend, but with an fig, (ax1m ax2) = plt.subplots( ncols=2)

all the other examples are pyplot 'cause it's only a line of code and I think that's a fairly clear distinction?

anntzer Sep 15, 2022

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I just got rid of the subplots, keeping only the second plot seems good enough.

Comment thread tutorials/introductory/images.py Outdated

###############################################################################
# Here we have the default interpolation, bilinear, since we did not
# Here we have the default interpolation ("nearest"), since we did not

story645 Sep 14, 2022

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# Here we have the default interpolation ("nearest"), since we did not
# Here we use the default interpolation ("nearest"), since we did not

tacaswell added this to the v3.7.0 milestone Sep 14, 2022
timhoffm reviewed Sep 14, 2022
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Comment thread tutorials/introductory/images.py Outdated
@@ -205,20 +199,19 @@
#
# You can specify the clim in the call to ``plot``.

timhoffm Sep 14, 2022

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

And its imshownotplot`, we are talking about.

Then maybe:

Suggested change
# You can specify the clim in the call to ``plot``.
# You can specify the colormap limits using ``imshow(..., clim=...)``.

Sorry, to comment on code you're not responsible for, but this is too glaringly wrong.

oscargus reviewed Sep 15, 2022
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Comment thread tutorials/introductory/images.py
from PIL import Image

img = Image.open('../../doc/_static/stinkbug.png')
img.thumbnail((64, 64), Image.ANTIALIAS) # resizes image in-place

oscargus Sep 15, 2022

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img.thumbnail((64, 64), Image.ANTIALIAS) # resizes image in-place
img.thumbnail((64, 64)) # resizes image in-place

May just as well put that here instead of #23881 (which can be closed then).

anntzer Sep 15, 2022

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I merged yours.

anntzer commented Sep 15, 2022

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Thanks, handled all comments (got rid of the subplots, as noted re: @story645's suggestion).

Update image tutorial.
cb71f65 
- Use Pillow to load the image rather than the discouraged plt.imread.
- Remove discussion about rescaling to 0-1 as dropping the use of
  plt.imread also gets rid of that (not so nice) behavior.  Also drop
  the lengthy discussion about uint8 and float32, which seems out of
  place here (if anything it should be in the Pillow docs).  Make
  corresponding fixes to code to use 0-255 instead of 0-1.
- Fix subplot management to go full pyplot (the local switch to
  OO-style is a bit weird).
- Fix interpolation discussion as the default is now "nearest" (actually
  it's now "antialiased", but let's sweep that under the rug for this
  tutorial for now).
timhoffm merged commit 2ff4dc9 into matplotlib:main Sep 15, 2022
anntzer deleted the imtut branch September 15, 2022 12:36
melissawm pushed a commit to melissawm/matplotlib that referenced this pull request Dec 19, 2022
Update image tutorial. (matplotlib#23889)
90b5e3e 
- Use Pillow to load the image rather than the discouraged plt.imread.
- Remove discussion about rescaling to 0-1 as dropping the use of
  plt.imread also gets rid of that (not so nice) behavior.  Also drop
  the lengthy discussion about uint8 and float32, which seems out of
  place here (if anything it should be in the Pillow docs).  Make
  corresponding fixes to code to use 0-255 instead of 0-1.
- Fix subplot management to go full pyplot (the local switch to
  OO-style is a bit weird).
- Fix interpolation discussion as the default is now "nearest" (actually
  it's now "antialiased", but let's sweep that under the rug for this
  tutorial for now).
imgbot Bot pushed a commit to kkipngenokoech/matplotlib that referenced this pull request Apr 19, 2026
Update image tutorial. (matplotlib#23889)
62eb065 
- Use Pillow to load the image rather than the discouraged plt.imread.
- Remove discussion about rescaling to 0-1 as dropping the use of
  plt.imread also gets rid of that (not so nice) behavior.  Also drop
  the lengthy discussion about uint8 and float32, which seems out of
  place here (if anything it should be in the Pillow docs).  Make
  corresponding fixes to code to use 0-255 instead of 0-1.
- Fix subplot management to go full pyplot (the local switch to
  OO-style is a bit weird).
- Fix interpolation discussion as the default is now "nearest" (actually
  it's now "antialiased", but let's sweep that under the rug for this
  tutorial for now).
imgbot Bot pushed a commit to kkipngenokoech/matplotlib that referenced this pull request Apr 19, 2026
Update image tutorial. (matplotlib#23889)
b3d42dd 
- Use Pillow to load the image rather than the discouraged plt.imread.
- Remove discussion about rescaling to 0-1 as dropping the use of
  plt.imread also gets rid of that (not so nice) behavior.  Also drop
  the lengthy discussion about uint8 and float32, which seems out of
  place here (if anything it should be in the Pillow docs).  Make
  corresponding fixes to code to use 0-255 instead of 0-1.
- Fix subplot management to go full pyplot (the local switch to
  OO-style is a bit weird).
- Fix interpolation discussion as the default is now "nearest" (actually
  it's now "antialiased", but let's sweep that under the rug for this
  tutorial for now).
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