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Plot Colorbar in axes_grid1 with pcolormesh #630

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Merged
merged 1 commit into from
Jan 1, 2012
Merged

Plot Colorbar in axes_grid1 with pcolormesh #630

merged 1 commit into from
Jan 1, 2012

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jenshnielsen
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This is identical to the standard colorbar and removes artifacts (white stripes)
in the pdf version of the ImageGrid plot.

The following example should illustrate the difference.

from __future__ import division
import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import ImageGrid,make_axes_locatable

F = plt.figure()
grid = ImageGrid(F, 111, # similar to subplot(111)
                 nrows_ncols = (2, 2),
                 axes_pad = 0.1,
                 add_all=True,
                 label_mode = "L",
                 share_all = True,
                 cbar_mode = "single",
                  )
data = np.arange(100).reshape(10,10)
for a in range(4):
    ax = grid[a]
    im = ax.imshow(data,interpolation='none',origin='lower')
v = grid.cbar_axes[0].colorbar(im)

plt.savefig('test_imagegrid.pdf')

Examples of the figures using current v1.1.x branch without and with the pcolormesh.

Before:
http://ubuntuone.com/5p9IYAFbFj9bbmN4A1dfo9
After:
http://ubuntuone.com/18vD21xtiQuVTFy96QVNOS

@jenshnielsen
use pcolormesh instead of pcolor in axes_grid1 colorbar
a62545d 
This is identical to the standard colorbar and removes artifacts
in the pdf version of the plot.
@Carreau
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Carreau commented Dec 16, 2011

Note that depending of the pdf reader you use the two above link might be pixel perfect corresponding images.
but I agree that the pdf reader which showed strips, it is fixed.

@jenshnielsen
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I did not investigate that.
But yes thats right. In adobe reader X they are rendered identical while they are different
in Okular, Evince and Xpdf. (Ubuntu 11.10)

@WeatherGod
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The white lines are a known issue and is entirely dependent upon the pdf viewers. So, the question that remains is, even though it is not a bug on our part, should we change to pcolormesh so that our users get a better quality product, or should we prod some of these projects to fix their viewers? Or both?

@jenshnielsen
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Yes I see. This it would indicate that the bug is in Cairo or Poppler since all 3 viewers use Poppler
and Poppler uses Cairo to render vector graphics.

In any case it seem strange that axisgrid1 method produces the white lines while the standard colorbar
does not. For a normal user this would indicate a bug in the axisgrid1 implementation. Also if one tries to add a normal colorbar to the figure using plt.colorbar() then this results in both a standard misplaced colorbar and another colorbar
on top of the axisgrid1 colorbar. Both of these have white stripes but shifted to make it look like the artifacts are gone.

efiring added a commit that referenced this pull request Jan 1, 2012
@efiring
Merge pull request #630 from jenshnielsen/colorbar
d23f721 
Plot Colorbar in axes_grid1 with pcolormesh
@efiring efiring merged commit d23f721 into matplotlib:v1.1.x Jan 1, 2012
@sargas sargas mentioned this pull request Aug 8, 2015
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4 participants
@jenshnielsen @Carreau @WeatherGod @efiring