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Added min_alpha parameter to shade and datashade #2109

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Nov 9, 2017
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8 changes: 7 additions & 1 deletion holoviews/operation/datashader.py
Original file line number Diff line number Diff line change
Expand Up @@ -530,6 +530,12 @@ class shade(Operation):
Disable when you do not want the resulting plot to be interactive,
e.g. when trying to display an interactive plot a second time.""")

min_alpha = param.Number(default=40, doc="""
The minimum alpha value to use for non-empty pixels when doing
colormapping, in [0, 255]. Use a higher value to avoid
undersaturation, i.e. poorly visible low-value datapoints, at
the expense of the overall dynamic range..""")

@classmethod
def concatenate(cls, overlay):
"""
Expand Down Expand Up @@ -577,7 +583,7 @@ def _process(self, element, key=None):

# Compute shading options depending on whether
# it is a categorical or regular aggregate
shade_opts = dict(how=self.p.normalization)
shade_opts = dict(how=self.p.normalization, min_alpha=self.p.min_alpha)
if element.ndims > 2:
kdims = element.kdims[1:]
categories = array.shape[-1]
Expand Down