Hello,

I'm (unsuccessfully) trying to generate a figure (with a labeled colorbar) having a black background.

Here is the code.

_purpose_ = 'demonstrate capability to create PNG with black background including labeled color bar'
_author_  = 'jim.vickroy@noaa.gov'

import numpy      # http://numpy.scipy.org/
import matplotlib # http://matplotlib.sourceforge.net/index.html
matplotlib.use('Agg') # http://matplotlib.sourceforge.net/backends.html -- probably the fastest, non-GUI, rendering backend
import matplotlib.pyplot as plot # http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot
import matplotlib.cm # color maps

import sys
assert sys.version            == '2.6.4 (r264:75708, Oct 26 2009, 08:23:19) [MSC v.1500 32 bit (Intel)]', sys.version
assert numpy.__version__      == '1.4.0',  numpy.__version__
assert matplotlib.__version__ == '0.99.1', matplotlib.__version__

data_min =   0
data_max = 256
data     = numpy.random.randint(data_max, size=(512,512))
rows_cnt, columns_cnt = data.shape
shape    = rows_cnt, columns_cnt
x        = numpy.empty(data.shape, dtype=int)
y        = numpy.empty(data.shape, dtype=int)
x[:]     = numpy.arange(rows_cnt)
y[:]     = numpy.arange(columns_cnt)
XI, YI   = numpy.meshgrid(x[0], y[0])

title      = 'this is the figure title'
plot.clf() # clear the figure
plot.title(title,color='white',backgroundcolor='black')
plot.axis('off')
colormap = 'gist_heat'
config   = dict(cmap=eval('matplotlib.cm.%s' % colormap), vmin=data_min, vmax=data_max) # vmin,vmax specify a fixed (color-map) scale
plot.pcolormesh(XI, YI, data, **config)
colorbar = plot.colorbar()
##############################################################################################################################################################
# labels   = ??? list of strings labels ???
labels = [str(i) for i in range(10)]
colorbar.ax.set_yticklabels(labels, color='white')
##############################################################################################################################################################
plot.imshow(data, interpolation='bilinear', cmap=config['cmap'], origin='upper', extent=[0,rows_cnt,0,columns_cnt])
# plot.show() # interactive
filename = 'trial-plot-with-labeled-colorbar.png'
plot.savefig(filename, facecolor='black')
plot.close()

which generates a figure with a black background and invisible (black) color bar labels.

I'm probably going about this completely wrong.

Questions:
  1. How do I get white color bar labels?
  2. How do I access the generated sequence of string labels (for use as the first set_yticklabels parameter) rather than artificially defining a list of labels?

Thanks,
-- jv