10000 Merge pull request #17888 from bdice/colormap-repr · matplotlib/matplotlib@068e0f4 · GitHub
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Merge pull request #17888 from bdice/colormap-repr
ENH: Add _repr_png_ and _repr_html_ to Colormap objects.
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‎doc/users/next_whats_new/colormap_repr.rst

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IPython representations for Colormap objects
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The `matplotlib.colors.Colormap` object now has image representations for
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IPython / Jupyter backends. Cells returning a color map on the last line will
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display an image of the color map.

‎lib/matplotlib/colors.py

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.. _xkcd color survey: https://xkcd.com/color/rgb/
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"""
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import base64
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from collections.abc import Sized
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import functools
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import io
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import itertools
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from numbers import Number
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import re
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from PIL import Image
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from PIL.PngImagePlugin import PngInfo
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import matplotlib as mpl
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import numpy as np
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import matplotlib.cbook as cbook
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from matplotlib import docstring
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"""
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raise NotImplementedError()
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def _repr_png_(self):
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"""Generate a PNG representation of the Colormap."""
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IMAGE_SIZE = (400, 50)
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X = np.tile(np.linspace(0, 1, IMAGE_SIZE[0]), (IMAGE_SIZE[1], 1))
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pixels = self(X, bytes=True)
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png_bytes = io.BytesIO()
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title = self.name + ' color map'
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author = f'Matplotlib v{mpl.__version__}, https://matplotlib.org'
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pnginfo = PngInfo()
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pnginfo.add_text('Title', title)
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pnginfo.add_text('Description', title)
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pnginfo.add_text('Author', author)
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pnginfo.add_text('Software', author)
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Image.fromarray(pixels).save(png_bytes, format='png', pnginfo=pnginfo)
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return png_bytes.getvalue()
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def _repr_html_(self):
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"""Generate an HTML representation of the Colormap."""
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png_bytes = self._repr_png_()
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png_base64 = base64.b64encode(png_bytes).decode('ascii')
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return ('<strong>' + self.name + '</strong>' +
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'<img ' +
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'alt="' + self.name + ' color map" ' +
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'title="' + self.name + '"' +
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'style="border: 1px solid #555;" ' +
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'src="data:image/png;base64,' + png_base64 + '">')
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class LinearSegmentedColormap(Colormap):
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"""

‎lib/matplotlib/tests/test_colors.py

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import copy
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import itertools
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from io import BytesIO
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import numpy as np
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from PIL import Image
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import pytest
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from numpy.testing import assert_array_equal, assert_array_almost_equal
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def test_DivergingNorm_deprecated():
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with pytest.warns(cbook.MatplotlibDeprecationWarning):
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norm = mcolors.DivergingNorm(vcenter=0)
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def test_repr_png():
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cmap = plt.get_cmap('viridis')
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png = cmap._repr_png_()
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assert len(png) > 0
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img = Image.open(BytesIO(png))
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assert img.width > 0
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assert img.height > 0
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assert 'Title' in img.text
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assert 'Description' in img.text
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assert 'Author' in img.text
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assert 'Software' in img.text
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def test_repr_html():
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cmap = plt.get_cmap('viridis')
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html = cmap._repr_html_()
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assert len(html) > 0
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assert cmap.name in html

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