I think that I have found the problem here. Line2D.draw() (and I presume
other Artist subclasses) calls
gc.set_foreground(self._color)
...
gc.set_alpha(self._alpha)
self._color is defined by the color kwarg, whether it be a hex value,
3-tuple, 4-tuple, or something else. self._alpha is defined by the alpha
kwarg, but if the alpha kwarg is None, it is not overwritten with color[3].
Therefore, using color=(R,G,B,A) does not set alpha correctly. I'm not sure
the best (i.e. most matplotlib-like) way to change this so that the A value
gets used iff alpha is None, but I've attached a patch that does it one way
(diff'ed against the github master, commit 67b1cd650f574f9c53ce). I know
the patch is less than ideal, as it adds kwarg-specific handling into a
place where none had previously been done, and it's also in a for loop.
Maybe it would be better to do the checking along with the scalex and scaley
pops?
Separately, I noticed that backend_bases.GraphicsContextBase.set_foreground
claims to only expect an RGB definition, and not an RGBA definition. As
such, I think that it should call
self._rgb = colors.colorConverter.to_rgb(fg)
instead of
self._rgb = colors.colorConverter.to_rgba(fg)
since that will make self._rgb a 3-tuple instead of a 4-tuple.
Ben
On Sat, Jul 23, 2011 at 3:13 PM, Ben Breslauer <bbresla...@gmail.com> wrote:
> Hi,
>
> I'm trying to fade some data, using alpha values, that I am plotting with
> Axes.plot(). I can recreate this problem with 1 line of pylab.plot. If I
> use
>
> pylab.plot([1,2,3],[1,4,9], color=(1,0,0,.2), linewidth=7)
>
> then I get the equivalent of
>
> pylab.plot([1,2,3],[1,4,9], color=(1,0,0), linewidth=7)
>
> i.e. it does not use the alpha value. However, if instead I use
>
> pylab.plot([1,2,3],[1,4,9], color=(1,0,0), linewidth=7, alpha=.2)
>
> then the line is faded out appropriately. The plot documentation indicates
> that RGBA tuples should be valid, so I'm wondering if this is a bug. Maybe
> alpha is defaulting to 1 or None and then not being overwritten if color is
> a 4-tuple?
>
> I'm using Arch Linux with kernel 2.6.39, matplotlib 1.0.1 from the Arch
> repo, and the Qt4 backend. My installed Qt version is 4.7.3, and I am using
> KDE 4.6.5. Below is verbose-debug output. Thanks for any help!
>
> Ben
>
>
> $HOME=/home/ben
> CONFIGDIR=/home/ben/.matplotlib
> matplotlib data path /usr/lib/python2.7/site-packages/matplotlib/mpl-data
> loaded rc file
> /usr/lib/python2.7/site-packages/matplotlib/mpl-data/matplotlibrc
> matplotlib version 1.0.1
> verbose.level debug
> interactive is False
> units is False
> platform is linux2
> loaded modules: ['heapq', 'numpy.core.info', 'distutils',
> 'numpy.lib.format', 'functools', 'pylab', '_bisect', 'subprocess',
> 'sysconfig', 'gc', 'matplotlib.tempfile', 'distutils.sysconfig',
> 'ctypes._endian', 'encodings.encodings', 'pyparsing', 'matplotlib.colors',
> 'numpy.core.numerictypes', 'numpy.testing.sys', 'numpy.lib.__future__',
> 'numpy.fft.types', 'numpy.ma.cPickle', 'struct',
> 'numpy.matrixlib.defmatrix', 'numpy.random.info', 'tempfile',
> 'numpy.compat.types', 'pprint', 'numpy.linalg', 'matplotlib.threading',
> 'numpy.core.machar', 'numpy.testing.types', 'numpy.testing', 'collections',
> 'numpy.polynomial.sys', 'unittest.sys', 'numpy.core.umath', 'unittest.main',
> 'distutils.types', 'numpy.testing.operator', 'numpy.core.scalarmath',
> 'numpy.ma.sys', 'zipimport', 'string', 'matplotlib.subprocess',
> 'numpy.testing.os', 'unittest.functools', 'numpy.lib.arraysetops',
> 'numpy.testing.unittest', 'numpy.lib.math', 'encodings.utf_8',
> 'matplotlib.__future__', 'unittest.types', 'unittest.util', '
> numpy.testing.re', 'numpy.version', 'numpy.lib.re', 'distutils.re',
> 'numpy.matrixlib.sys', 'ctypes.os', 'numpy.core.os', 'numpy.lib.type_check',
> 'numpy.compat.sys', 'unittest.StringIO', 'bisect', 'numpy.core._internal',
> 'signal', 'numpy.lib.types', 'numpy.lib._datasource', 'random',
> 'numpy.lib.__builtin__', 'numpy.fft.fftpack_lite', 'matplotlib.cbook',
> 'textwrap', 'numpy.core.multiarray', 'numpy.polynomial.string',
> 'distutils.version', 'cStringIO', 'numpy.polynomial', 'numpy.numpy',
> 'matplotlib.StringIO', 'unittest.time', 'locale', 'numpy.add_newdocs',
> 'unittest.difflib', 'numpy.core.getlimits', 'base64', '_ssl',
> 'numpy.lib.sys', 'encodings', 'numpy.ma.itertools', 'unittest.pprint', '
> unittest.re', 'abc', 'numpy.matrixlib', 'numpy.ctypes',
> 'numpy.testing.decorators', 'matplotlib.warnings', 'rfc822',
> 'numpy.lib.npyio', 'numpy.lib.numpy', 'matplotlib.sys', 're',
> 'numpy.lib._compiled_base', 'numpy.polynomial.legendre', 'threading', 'new',
> 'numpy.ma.warnings', 'numpy.random.mtrand', 'urllib2', 'matplotlib.cPickle',
> 'math', 'numpy.fft.helper', 'fcntl', 'unittest.case', 'matplotlib.numpy',
> 'UserDict', 'unittest.suite', 'numpy.lib.function_base', 'distutils.os',
> 'matplotlib', 'numpy.fft.numpy', 'exceptions', 'numpy.lib.info', 'ctypes',
> 'numpy.lib.warnings', 'ctypes.struct', 'codecs', 'numpy.core._sort',
> 'numpy.os', 'unittest.loader', '_functools', '_locale', 'numpy.__builtin__',
> 'matplotlib.os', 'thread', 'StringIO', 'numpy.core.memmap', 'traceback',
> 'numpy.testing.warnings', 'weakref', 'itertools', 'numpy.fft.fftpack',
> 'numpy.linalg.lapack_lite', 'numpy.ma', 'distutils.sys', 'os', 'marshal',
> 'numpy.lib.itertools', '__future__', '_collections', 'urllib',
> 'matplotlib.traceback', '_sre', 'unittest', 'numpy.core.sys',
> 'numpy.random', 'numpy.linalg.numpy', '__builtin__',
> 'numpy.lib.twodim_base', 'numpy.ma.core', 'matplotlib.re',
> 'numpy.core.cPickle', 'unittest.runner', 'operator',
> 'numpy.polynomial.polytemplate', 'numpy.core.arrayprint',
> 'distutils.string', 'numpy.lib.arrayterator', 'select', 'ctypes._ctypes',
> '_heapq', 'ctypes.sys', 'matplotlib.errno', 'unittest.collections',
> 'posixpath', 'numpy.lib.financial', 'numpy.polynomial.laguerre',
> 'matplotlib.random', 'errno', '_socket', 'binascii', 'sre_constants',
> 'datetime', 'numpy.core.shape_base', 'os.path', 'numpy.core.function_base',
> 'numpy.compat.py3k', 'numpy.lib.stride_tricks', 'numpy.core.numpy', 'numpy',
> '_warnings', 'numpy.polynomial.chebyshev', 'matplotlib.types', 'cPickle',
> 'encodings.__builtin__', 'numpy.polynomial.warnings', 'matplotlib.new',
> '_codecs', 'numpy.lib.operator', 'unittest.fnmatch',
> 'numpy.polynomial.polynomial', 'numpy.__config__', 'pwd',
> 'matplotlib.pyparsing', 'httplib', 'numpy.lib.ufunclike', 'copy', '
> numpy.core.re', '_struct', 'numpy.core.fromnumeric', 'hashlib',
> 'numpy.ctypeslib', 'keyword', 'array', 'numpy.lib.scimath', 'numpy.fft',
> 'numpy.lib', 'numpy.ma.numpy', 'numpy.random.numpy', 'matplotlib.urllib2',
> 'unittest.weakref', 'numpy.ma.extras', 'numpy.polynomial.__future__',
> 'posix', 'encodings.aliases', 'matplotlib.fontconfig_pattern', 'fnmatch',
> 'sre_parse', 'pickle', 'numpy.core.ctypes', 'mimetools',
> 'distutils.distutils', 'unittest.signal', 'copy_reg', 'sre_compile',
> '_hashlib', '_random', '_ctypes', 'site', 'numpy.lib.polynomial',
> 'numpy.compat', 'numpy._import_tools', 'numpy.polynomial.hermite',
> '__main__', 'numpy.fft.info', 'numpy.core.records', 'shutil',
> 'numpy.lib.cPickle', 'numpy.sys', 'numpy.polynomial.hermite_e', 'urlparse',
> 'unittest.result', 'strop', 'grp', 'linecache', 'numpy.polynomial.numpy',
> 'numpy.core.numeric', 'numpy.linalg.info', 'encodings.codecs', '_abcoll',
> 'numpy.core', 'matplotlib.locale', 'matplotlib.rcsetup', 'matplotlib.time',
> 'matplotlib.weakref', 'genericpath', 'stat', 'socket', 'numpy.lib._iotools',
> 'numpy.lib.index_tricks', 'numpy.testing.utils', 'warnings',
> 'numpy.lib.utils', 'numpy.core.defchararray', 'numpy.polynomial.polyutils',
> 'numpy.lib.shape_base', 'numpy.core.types', 'unittest.signals', 'sys',
> 'numpy.core.warnings', 'numpy.compat._inspect', 'numpy.core.__builtin__',
> 'ctypes.ctypes', 'numpy.testing.traceback', 'numpy.lib.os',
> 'numpy.testing.nosetester', 'types', 'numpy.lib.shutil',
> 'matplotlib.datetime', 'matplotlib.distutils', '_weakref',
> 'numpy.testing.numpytest', 'difflib', 'distutils.errors',
> 'numpy.matrixlib.numpy', 'matplotlib.matplotlib', '_weakrefset',
> 'matplotlib.shutil', 'numpy.lib.cStringIO', 'unittest.warnings', 'time',
> 'unittest.traceback', 'ssl', 'numpy.linalg.linalg', 'unittest.os',
> 'numpy.testing.numpy']
> Using fontManager instance from /home/ben/.matplotlib/fontList.cache
> backend Qt4Agg version 0.9.1
> findfont: Matching
> :family=sans-serif:style=normal:variant=normal:weight=normal:stretch=normal:size=medium
> to Bitstream Vera Sans
> (/usr/lib/python2.7/site-packages/matplotlib/mpl-data/fonts/ttf/Vera.ttf)
> with score of 0.000000
>
>
*** axes.py.orig 2011-07-25 14:14:13.969881251 -0400
--- axes.py 2011-07-25 14:14:46.369705725 -0400
***************
*** 3819,3838 ****
--- 3819,3840 ----
whether the *x* and *y* axes are autoscaled; the default is
*True*.
"""
scalex = kwargs.pop( 'scalex', True)
scaley = kwargs.pop( 'scaley', True)
if not self._hold: self.cla()
lines = []
for line in self._get_lines(*args, **kwargs):
+ if len(line._color) == 4 and line._alpha == None:
+ line._alpha = line._color[3]
self.add_line(line)
lines.append(line)
self.autoscale_view(scalex=scalex, scaley=scaley)
return lines
@docstring.dedent_interpd
def plot_date(self, x, y, fmt='bo', tz=None, xdate=True, ydate=False,
**kwargs):
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