8000 Support pixel-by-pixel alpha in imshow. · matplotlib/matplotlib@19fa770 · GitHub
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tillahoffmanntillahoffmann
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Support pixel-by-pixel alpha in imshow.
1 parent 6c4bc56 commit 19fa770

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6 files changed

+232
-3
lines changed

6 files changed

+232
-3
lines changed

‎lib/matplotlib/axes/_axes.py

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -5517,9 +5517,11 @@ def imshow(self, X, cmap=None, norm=None, aspect=None,
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which can be set by *filterrad*. Additionally, the antigrain image
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resize filter is controlled by the parameter *filternorm*.
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alpha : scalar, optional
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alpha : [scalar | array_like], optional, default: None
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The alpha blending value, between 0 (transparent) and 1 (opaque).
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This parameter is ignored for RGBA input data.
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If `alpha` is an array, the alpha blending values are applied pixel
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by pixel, and `alpha` must have the same shape as `X`. This
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parameter is ignored for RGBA input data.
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vmin, vmax : scalar, optional
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When using scalar data and no explicit *norm*, *vmin* and *vmax*

‎lib/matplotlib/image.py

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -257,6 +257,7 @@ def __init__(self, ax,
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self.axes = ax
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self._imcache = None
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self._array_alpha = None
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self.update(kwargs)
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@@ -281,7 +282,11 @@ def set_alpha(self, alpha):
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----------
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alpha : float
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"""
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martist.Artist.set_alpha(self, alpha)
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if np.isscalar(alpha):
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martist.Artist.set_alpha(self, alpha)
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else:
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self._array_alpha = alpha
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martist.Artist.set_alpha(self, 1.0)
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self._imcache = None
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def changed(self):
@@ -487,6 +492,10 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
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# pixel it will be between [0, 1] (such as a rotated image).
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out_mask = np.isnan(out_alpha)
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out_alpha[out_mask] = 1
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# Apply the pixel-by-pixel alpha values if present
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if self._array_alpha is not None:
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out_alpha *= _resample(self, self._array_alpha, out_shape,
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t, resample=True)
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# mask and run through the norm
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output = self.norm(np.ma.masked_array(A_resampled, out_mask))
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else:

‎lib/matplotlib/tests/baseline_images/test_image/image_array_alpha.pdf

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‎lib/matplotlib/tests/baseline_images/test_image/image_array_alpha.png

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‎lib/matplotlib/tests/baseline_images/test_image/image_array_alpha.svg

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‎lib/matplotlib/tests/test_image.py

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1083,3 +1083,17 @@ def test_deprecation():
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with pytest.warns(MatplotlibDeprecationWarning):
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# Enough arguments to pass "shape" positionally.
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obj.imshow(data, *[None] * 10)
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@image_comparison(baseline_images=['image_array_alpha'], remove_text=True)
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def test_image_array_alpha():
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'''per-pixel alpha channel test'''
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x = np.linspace(0, 1)
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xx, yy = np.meshgrid(x, x)
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zz = np.exp(- 3 * ((xx - 0.5) ** 2) + (yy -0.7 ** 2))
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alpha = zz / zz.max()
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fig = plt.figure()
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ax = fig.add_subplot(111)
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ax.imshow(zz, alpha=alpha)

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