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Commitab6e305

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Clip invalid values in RGB imshow to bounds
1 parent18b6b06 commitab6e305

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2 files changed

+19
-1
lines changed

2 files changed

+19
-1
lines changed

‎doc/users/next_whats_new/2018_01_11_imshow-rgb-scaling-clipping.rst

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@@ -4,3 +4,7 @@
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`Axes.imshow` can now apply the ``norm`` or ``vmin`` and ``vmax`` arguments
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to RGB images, allowing easy display of high-bit-depth data, or adjustments
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of brightness and contrast.
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Out-of-range values in un-normalised RGB and RGBA images are now clipped to
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the nearest bound, rather than being wrapped. This bug often hid outliers,
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and could make interpretation of the plotted image entirely unreliable.

‎lib/matplotlib/axes/_axes.py

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@@ -5237,7 +5237,7 @@ def imshow(self, X, cmap=None, norm=None, aspect=None,
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Elements of RGB and RGBA arrays represent pixels of an MxN image.
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All values - unless normalised with `norm` or `vmin` and `vmax` -
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should be in the range [0 .. 1] for floats or [0 .. 255] for
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integers.
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integers. Out-of-range values will be clipped to these bounds.
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cmap : `~matplotlib.colors.Colormap`, optional, default: None
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If None, default to rc `image.cmap` value. `cmap` is ignored
@@ -5362,6 +5362,20 @@ def imshow(self, X, cmap=None, norm=None, aspect=None,
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# Disable later styling based on these values
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norm,vmin,vmax=None,None,None
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# If the input data has values outside the valid range (after
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# normalisation), we issue a warning and then clip X to the bounds
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# - otherwise casting wraps extreme values, hiding outliers and
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# making reliable interpretation impossible.
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high_bound=255ifnp.issubdtype(X.dtype,np.integer)else1
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ifX.min()<0orhigh_bound<X.max():
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warnings.warn(
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'Clipping input data to the valid range for imshow with '
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'RGB data ([0..1] for floats or [0..255] for integers). '
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'Pass the `norm`, `vmin`, or `vmax` arguments to avoid '
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'this error.'
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)
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X=np.clip(X,0,high_bound)
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im=mimage.AxesImage(self,cmap,norm,interpolation,origin,extent,
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filternorm=filternorm,filterrad=filterrad,
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resample=resample,**kwargs)

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