Bug: alpha parameter was ignored when fill color is #000000

[kshramt]

ax.scatter(xs, ys, alpha=0.1, c='k') did not produce transparent dots.

[mdboom]

Would you mind including a regression test? (The current failures seem unrelated to this and are on master as well. You can ignore them until I fix master).

[pelson]

Looks good. I like the test image:

[mdboom]

Good test. Would you mind adding "remove_text=True" here to remove the text (just to make the test image file size smaller?)

[kshramt]

A new test image is:

[mdboom]

Thanks. We're getting this test failure on Travis, Python 2.x only. (The other test failure is unrelated and can be ignored). I think the issue is the use of alpha='0.1' as a string.

======================================================================
ERROR: test suite for <class 'matplotlib.tests.test_backend_svg.test_fill_black_with_alpha'>
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/virtualenv/python2.6/lib/python2.6/site-packages/nose/plugins/multiprocess.py", line 788, in run
    self.setUp()
  File "/home/travis/virtualenv/python2.6/lib/python2.6/site-packages/nose/suite.py", line 291, in setUp
    self.setupContext(ancestor)
  File "/home/travis/virtualenv/python2.6/lib/python2.6/site-packages/nose/plugins/multiprocess.py", line 770, in setupContext
    super(NoSharedFixtureContextSuite, self).setupContext(context)
  File "/home/travis/virtualenv/python2.6/lib/python2.6/site-packages/nose/suite.py", line 314, in setupContext
    try_run(context, names)
  File "/home/travis/virtualenv/python2.6/lib/python2.6/site-packages/nose/util.py", line 469, in try_run
    return func()
  File "/home/travis/virtualenv/python2.6/lib/python2.6/site-packages/matplotlib-1.4.x-py2.6-linux-x86_64.egg/matplotlib/testing/decorators.py", line 105, in setup_class
    cls._func()
  File "/home/travis/virtualenv/python2.6/lib/python2.6/site-packages/matplotlib-1.4.x-py2.6-linux-x86_64.egg/matplotlib/tests/test_backend_svg.py", line 43, in test_fill_black_with_alpha
    ax.scatter(x=[0, 0.1, 1], y=[0, 0, 0], c='k', alpha='0.1', s=10000)
  File "/home/travis/virtualenv/python2.6/lib/python2.6/site-packages/matplotlib-1.4.x-py2.6-linux-x86_64.egg/matplotlib/axes/_axes.py", line 3280, in scatter
    collection.set_alpha(alpha)
  File "/home/travis/virtualenv/python2.6/lib/python2.6/site-packages/matplotlib-1.4.x-py2.6-linux-x86_64.egg/matplotlib/collections.py", line 607, in set_alpha
    self._facecolors_original, self._alpha)
  File "/home/travis/virtualenv/python2.6/lib/python2.6/site-packages/matplotlib-1.4.x-py2.6-linux-x86_64.egg/matplotlib/colors.py", line 404, in to_rgba_array
    raise ValueError("alpha must be in 0-1 range")
ValueError: alpha must be in 0-1 range

[kshramt]

Tests on Travis-CI seems to have been stopped due to some error from apt-get.
Would you visit https://travis-ci.org/matplotlib/matplotlib/builds/11326417 and push a rebuild button?

E: Some index files failed to download. They have been ignored, or old ones used instead.
The command "sudo apt-get update" failed and exited with 100 during install.
Your build has been stopped.

[mdboom]

Restart pushed.

[kshramt]

Thanks!

[pelson]

@kshramt - I'm happy to merge this, but I think we should squash your commits into one. Something like:

git rebase -i HEAD~4

Details at http://gitready.com/advanced/2009/02/10/squashing-commits-with-rebase.html

Cheers!