Michael Hearne wrote:
> Ryan - Thanks for your response.
>
> Shouldn't a color dictionary have 4 "columns" - a value, and the
> corresponding R,G,B values? If I understand your response, the "row"
> with 0.2 as the first column has only two values. How does
> LinearSegmentedColormap derive an RGB triplet from those two numbers?
>
Not quite. I'm pretty sure I was a little vague in my last message, so
let me be more concrete. Here's an example of a 5 gray level color map
data dictionary:
_Gray5_data = {'blue': [(0.0, 0.42352941176470588, 0.42352941176470588),
(0.25, 0.53333333333333333, 0.53333333333333333),
(0.5, 0.6588235294117647, 0.6588235294117647),
(0.75, 0.81568627450980391, 0.81568627450980391),
(1.0, 0.93725490196078431, 0.93725490196078431)],
'green': [(0.0, 0.42352941176470588, 0.42352941176470588),
(0.25, 0.53333333333333333, 0.53333333333333333),
(0.5, 0.6588235294117647, 0.6588235294117647),
(0.75, 0.81568627450980391, 0.81568627450980391),
(1.0, 0.93725490196078431, 0.93725490196078431)],
'red': [(0.0, 0.42352941176470588, 0.42352941176470588),
(0.25, 0.53333333333333333, 0.53333333333333333),
(0.5, 0.6588235294117647, 0.6588235294117647),
(0.75, 0.81568627450980391, 0.81568627450980391),
(1.0, 0.93725490196078431, 0.93725490196078431)]}
Note that the dictionary contains one list each for red, green, and
blue. Each entry in the a list for the color corresponds to an entry in
the table. This entry has 3 pieces of information: The first (item #1)
is the corresponding normalized data value for this color (between 0 and
1). The next two values are normalized color values, the first if the
actual data value is below the value in item #1 and the 2nd if it is
above. In the case of the one above, the color is the same regardless.
So, for example, a normalized data value of 0.25 gets an RGB tuple of
(0.5333,0.5333,0.5333).
HTH,
Ryan
--
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma
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