Hi, folks. OK, I'm trying to set the alpha channel, pixel by pixel, using
figimage w/ the data being of the "luminance" type (i.e., an MxN array). The
Users Guide indicates that figimage takes an alpha= keyword argument, and it
doesn't crash when I pass an array for this value, but subsequently when I try
to draw it using fig.draw(canvas.get_renderer()), I get:
>>> fig.draw(canvas.get_renderer())
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\python25\lib\site-packages\matplotlib\figure.py", line 607, in draw
im.draw(renderer)
File "C:\python25\lib\site-packages\matplotlib\image.py", line 597, in draw
im = self.make_image()
File "C:\python25\lib\site-packages\matplotlib\image.py", line 583, in make_im
age
x = self.to_rgba(self._A, self._alpha)
File "C:\python25\lib\site-packages\matplotlib\cm.py", line 76, in to_rgba
x = self.cmap(x, alpha=alpha, bytes=bytes)
File "C:\python25\lib\site-packages\matplotlib\colors.py", line 423, in __call
__
alpha = min(alpha, 1.0) # alpha must be between 0 and 1
ValueError: The truth value of an array with more than one element is ambiguous.
Use a.any() or a.all()
which to me "smells" as if the array-valued alpha is the problem.
Clearly (?) I can do what I'm after if I use MxNx4 data, but is that the only
way to have a varying alpha?
Thanks!
DG
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