I use matplotlib pcolormesh plots with colorbars, apply rasterization to the plots and colorbars in order to reduce the file size and save the figure as a PDF file. Thereby I noticed, that after rasterization the color-area itself shifts a bit with respect to the axes towards up and left, so that a white stripe at the lower and right edge of the plot appears. Same happens to the colorbar, which I found even worse: with thin colorbars, the white stripe is very obvious and disturbing. Is there a way to avoid this behaviour of rasterized plots and to keep the rasterized area at the same place as before rasterization?
I tried to play around with rasterization_zorder and zorder settings. It helped a bit with the pcolormesh plots (the lower white stripe disappeared), but I found no way to apply it to the colorbar.
Down there is a simple example with four plots demonstrating the problem. Please zoom in into the PDF file at the lower right edges of the plots to see what I mean.
import numpy as np
import matplotlib.pyplot as plt
d = np.arange(100).reshape(10, 10)
myfig = plt.figure(figsize=(5, 5))
'''plot 1, no rasterization'''
ax1 = plt.subplot(221)
plot1 = ax1.pcolormesh(d)
cbar1 = plt.colorbar(plot1)
ax1.set_title("no rasterization", fontsize = 10)
'''plot 2, main plot rasterized, colorbar not'''
ax2 = plt.subplot(222)
plot2 = ax2.pcolormesh(d, rasterized=True)
cbar2 = plt.colorbar(plot2)
ax2.set_title("plot rasterized", fontsize = 10)
'''plot 3, main plot and colorbar rasterized'''
ax3 = plt.subplot(223)
plot3 = ax3.pcolormesh(d, rasterized=True)
cbar3 = plt.colorbar(plot3)
cbar3.solids.set_rasterized(True) # !!!!!!!!
ax3.set_title("plot and cbar rasterized", fontsize = 10)
'''plot 4, whole axes of main plot and colorbar rasterized, attempt to use rasterization_zorder'''
ax4 = plt.subplot(224)
ax4.set_rasterization_zorder(-10)
plot4 = ax4.pcolormesh(d, zorder=-20)
'''colorbarbar gets its own axis'''
from mpl_toolkits.axes_grid1.inset_locator import inset_axes
ax_cbar4 = inset_axes(ax4, width="3%", height="100%", loc=6)
ax_cbar4.set_rasterization_zorder(-10)
locator_ax_cbar4 =ax_cbar4.get_axes_locator()
locator_ax_cbar4.set_bbox_to_anchor ((1.0, 0 , 1, 1), ax4.transAxes)
cbar4=plt.colorbar(plot4, cax=ax_cbar4)
#cbar4.solids.set_rasterization_zorder(-10) # ---> NOT WORKING
cbar4.solids.set_rasterized(True)
ax4.set_title("axes rasterized and zorder changed", fontsize = 10)
plt.savefig("D:/test_rasterization_3plots.pdf", dpi=150)
print 'pdf file saved'
plt.show()
Any suggestions will be appreciated!