Re: [Matplotlib-users] how to define custom colormap from set of RGB values ?

[<PHobson@Geosyntec.com>]

Give this a shot:
http://www.scipy.org/Cookbook/Matplotlib/Show_colormaps

From: Jim Vickroy [mailto:Jim...@no...]
Sent: Wednesday, June 16, 2010 8:14 AM
To: Matplotlib
Subject: [Matplotlib-users] how to define custom colormap from set of RGB values ?

Hello,

The attached script shows my (failed) attempt to define a custom color map from a set of RGB values (taken from an IDL palette).

My approach is presumably completely wrong, but I have not found information or examples on how to do this.

Could someone point in the right direction?

Thanks,

-- jv

P.S.
When run on my workstation, the output from the attached script is:

<output>
Python version:     2.6.4 (r264:75708, Oct 26 2009, 08:23:19) [MSC v.1500 32 bit (Intel)]
matplotlib version: 0.99.3
numpy version:      1.4.0
Traceback (most recent call last):
  File "custom-colormap.py", line 97, in <module>
    plotter.savefig('%s.png' %colormap.name, facecolor='black', edgecolor='black')
  File "C:\Python26\lib\site-packages\matplotlib\pyplot.py", line 356, in savefig
    return fig.savefig(*args, **kwargs)
  File "C:\Python26\lib\site-packages\matplotlib\figure.py", line 1032, in savefig
    self.canvas.print_figure(*args, **kwargs)
  File "C:\Python26\lib\site-packages\matplotlib\backend_bases.py", line 1476, in print_figure
    **kwargs)
  File "C:\Python26\lib\site-packages\matplotlib\backends\backend_agg.py", line 358, in print_png
    FigureCanvasAgg.draw(self)
  File "C:\Python26\lib\site-packages\matplotlib\backends\backend_agg.py", line 314, in draw
    self.figure.draw(self.renderer)
  File "C:\Python26\lib\site-packages\matplotlib\artist.py", line 46, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python26\lib\site-packages\matplotlib\figure.py", line 773, in draw
    for a in self.axes: a.draw(renderer)
  File "C:\Python26\lib\site-packages\matplotlib\artist.py", line 46, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python26\lib\site-packages\matplotlib\axes.py", line 1701, in draw
    im.draw(renderer)
  File "C:\Python26\lib\site-packages\matplotlib\artist.py", line 46, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python26\lib\site-packages\matplotlib\image.py", line 237, in draw
    im = self.make_image(renderer.get_image_magnification())
  File "C:\Python26\lib\site-packages\matplotlib\image.py", line 182, in make_image
    x = self.to_rgba(self._A, self._alpha)
  File "C:\Python26\lib\site-packages\matplotlib\cm.py", line 167, in to_rgba
    x = self.cmap(x, alpha=alpha, bytes=bytes)
  File "C:\Python26\lib\site-packages\matplotlib\colors.py", line 489, in __call__
    if not self._isinit: self._init()
  File "C:\Python26\lib\site-packages\matplotlib\colors.py", line 720, in _init
    for c in self.colors], np.float)
  File "C:\Python26\lib\site-packages\matplotlib\colors.py", line 311, in to_rgb
    raise ValueError('to_rgb: Invalid rgb arg "%s"\n%s' % (str(arg), exc))
ValueError: to_rgb: Invalid rgb arg "(0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 2, 3, 4, 4, 5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 22, 23, 25, 26, 28, 29, 31, 33, 34, 36, 38,
40, 41, 43, 45, 47, 49, 50, 53, 55, 57, 59, 61, 64, 66, 68, 70, 72, 74, 76, 79, 82, 84, 87, 89, 91, 94, 96, 99, 101, 104, 106, 108, 110, 113, 116, 118, 121, 124, 127, 128, 131, 134, 137
, 138, 141, 144, 147, 149, 152, 155, 156, 160, 161, 164, 168, 169, 172, 174, 177, 179, 182, 184, 188, 189, 191, 195, 196, 198, 202, 203, 205, 209, 211, 212, 214, 216, 220, 222, 224, 225
, 227, 229, 231, 233, 235, 237, 239, 241, 243, 245, 247, 249, 251, 253, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255
, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255
, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255
, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255)"
sequence length is 256; must be 3 or 4
</output>