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Cairo backend: Fix alpha render of collections #12774

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Merged
merged 1 commit into from
Nov 28, 2018
Merged

Cairo backend: Fix alpha render of collections #12774

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51 changes: 0 additions & 51 deletions lib/matplotlib/backends/backend_cairo.py
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Original file line number Diff line number Diff line change
Expand Up @@ -286,57 +286,6 @@ def draw_markers(self, gc, marker_path, marker_trans, path, transform,
self._fill_and_stroke(
ctx, rgbFace, gc.get_alpha(), gc.get_forced_alpha())

def draw_path_collection(
self, gc, master_transform, paths, all_transforms, offsets,
offsetTrans, facecolors, edgecolors, linewidths, linestyles,
antialiaseds, urls, offset_position):

path_ids = [
(path, Affine2D(transform))
for path, transform in self._iter_collection_raw_paths(
master_transform, paths, all_transforms)]

reuse_key = None
grouped_draw = []

def _draw_paths():
if not grouped_draw:
return
gc_vars, rgb_fc = reuse_key
gc = copy.copy(gc0)
# We actually need to call the setters to reset the internal state.
vars(gc).update(gc_vars)
for k, v in gc_vars.items():
if k == "_linestyle": # Deprecated, no effect.
continue
try:
getattr(gc, "set" + k)(v)
except (AttributeError, TypeError) as e:
pass
gc.ctx.new_path()
paths, transforms = zip(*grouped_draw)
grouped_draw.clear()
_append_paths(gc.ctx, paths, transforms)
self._fill_and_stroke(
gc.ctx, rgb_fc, gc.get_alpha(), gc.get_forced_alpha())

for xo, yo, path_id, gc0, rgb_fc in self._iter_collection(
gc, master_transform, all_transforms, path_ids, offsets,
offsetTrans, facecolors, edgecolors, linewidths, linestyles,
antialiaseds, urls, offset_position):
path, transform = path_id
transform = (Affine2D(transform.get_matrix())
.translate(xo, yo - self.height).scale(1, -1))
# rgb_fc could be a ndarray, for which equality is elementwise.
new_key = vars(gc0), tuple(rgb_fc) if rgb_fc is not None else None
if new_key == reuse_key:
grouped_draw.append((path, transform))
else:
_draw_paths()
grouped_draw.append((path, transform))
reuse_key = new_key
_draw_paths()

def draw_image(self, gc, x, y, im):
im = cbook._unmultiplied_rgba8888_to_premultiplied_argb32(im[::-1])
surface = cairo.ImageSurface.create_for_data(
Expand Down
55 changes: 55 additions & 0 deletions lib/matplotlib/tests/test_backend_cairo.py
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Original file line number Diff line number Diff line change
@@ -0,0 +1,55 @@
import numpy as np
from io import BytesIO
import os
import tempfile
import warnings
import xml.parsers.expat

import pytest

import matplotlib.pyplot as plt
from matplotlib.testing.decorators import check_figures_equal
import matplotlib
from matplotlib import (
collections as mcollections, patches as mpatches, path as mpath)


@pytest.mark.backend('cairo')
@check_figures_equal(extensions=["png"])
def test_patch_alpha_coloring(fig_test, fig_ref):
"""
Test checks that the patch and collection are rendered with the specified
alpha values in their facecolor and edgecolor.
"""
star = mpath.Path.unit_regular_star(6)
circle = mpath.Path.unit_circle()
# concatenate the star with an internal cutout of the circle
verts = np.concatenate([circle.vertices, star.vertices[::-1]])
codes = np.concatenate([circle.codes, star.codes])
cut_star1 = mpath.Path(verts, codes)
cut_star2 = mpath.Path(verts + 1, codes)

# Reference: two separate patches
ax = fig_ref.subplots()
ax.set_xlim([-1, 2])
ax.set_ylim([-1, 2])
patch = mpatches.PathPatch(cut_star1,
linewidth=5, linestyle='dashdot',
facecolor=(1, 0, 0, 0.5),
edgecolor=(0, 0, 1, 0.75))
ax.add_patch(patch)
patch = mpatches.PathPatch(cut_star2,
linewidth=5, linestyle='dashdot',
facecolor=(1, 0, 0, 0.5),
edgecolor=(0, 0, 1, 0.75))
ax.add_patch(patch)

# Test: path collection
ax = fig_test.subplots()
ax.set_xlim([-1, 2])
ax.set_ylim([-1, 2])
col = mcollections.PathCollection([cut_star1, cut_star2],
linewidth=5, linestyles='dashdot',
facecolor=(1, 0, 0, 0.5),
edgecolor=(0, 0, 1, 0.75))
ax.add_collection(col)