def create_cmap(start,
end,
mid=None,
N=256,
extend='neither',
over=None,
under=None,
normalize=None):
"""
Function that creates matplotlib colormaps. Note that input colors must
be RGB tuples within [0,1].
Parameters
----------
start : 3-tuple
RGB-Tuple defining the start color of the color map.
end : 3-tuple
RGB-Tuple defining the end color of the color map.
mid : list (optional, default = None)
List of tuples (pos, col) specifying any colors in between start and
end. In this context, 0. < pos < 1. specifiies the position of col
(passed as RGB tuple) within the color map range.
N : int (optional, default = 256)
The number of rgb quantization levels.
extend : string (optional, one of {*'neither'*, 'both', 'max', 'min'})
Extend the colorbar and indicate this by triangles at the respective
ends. See eg. here:
http://matplotlib.org/examples/pylab_examples/contourf_demo.html
over : 3-tuple (optional, default = None)
Color definition for everything out of the upper range of the colormap.
This is only meaningful if you set the ``extend`` option correctly.
Uses ``end`` by default.
under : 3-tuple (optional, default = None)
Same as ``over`` but for the lower limit. Uses ``start`` by default.
Returns
-------
cmap : LinearSegmentedColormap instance
color map, ready to be used with matplotlib.
Examples
--------
If you want a colormap ranging from tumblue over white to tumorange, you
call this function via
>>> cmap = create_cmap(start = tumcolors['tumblue'],
end = tumcolors['tumorange'],
mid = [(0.5, tumcolors['white'])]
)
You can also go straight from tumblue to tumorange:
>>> cmap = create_cmap(start = tumcolors['tumblue'],
end = tumcolors['tumorange'])
Or you can add several colors in between:
>>> cmap = create_cmap(start = tumcolors['tumblue'],
end = tumcolors['tumorange'],
mid = [(0.3, tumcolors['white']),
(0.7, tumcolors['black'])]
)
"""
from matplotlib.colors import LinearSegmentedColormap
cdict = dict()
for i, channel in enumerate(['red', 'green', 'blue']):
cdict_content = [[0.0, start[i], start[i]]]
if mid is not None:
try:
for pos, col in mid:
cdict_content.append([pos, col[i], col[i]])
except TypeError:
pos, col = mid
cdict_content.append([pos, col[i], col[i]])
cdict_content.append([1.0, end[i], end[i]])
cdict[channel] = cdict_content
cmap = LinearSegmentedColormap('custom_cmap', cdict, N)
# extend
cmap.colorbar_extend = extend
if under is None:
under = start
if over is None:
over = end
cmap.set_over(over)
cmap.set_under(under)
return cmap
