Transparencey issue using hybrid style from GoogleTiles

[mattijn]

In the code comment is mentioned that it is possible to get hybrid style form google by using only_streets and satellite

# Only streets are partly transparent tiles that can be overlayed over
# the satellite map to create the known hybrid style from google.

But by using this code:

import matplotlib.pyplot as plt
import cartopy.crs as ccrs
from cartopy.io import img_tiles
%matplotlib inline

tiles_sat = img_tiles.GoogleTiles(style='satellite')
tiles_str = img_tiles.GoogleTiles(style='only_streets')
web_merc = img_tiles.GoogleTiles().crs
img_extent = (31, 35.5, 34, 36)

ax = plt.axes(projection=web_merc)
plt.title('Cyprus')
ax.set_extent([31, 35.5, 34, 36], ccrs.Geodetic())
ax.coastlines(resolution='10m')
ax.add_image(tiles_sat, 8)
ax.add_image(tiles_str, 8)

plt.show()

It won't give a transparent, but one with a black background.
Am I missing something?

[QuLogic]

Probably this warning that shows up indicates what needs to be fixed here:

/usr/lib64/python3.4/site-packages/PIL/Image.py:861: UserWarning: Palette images with Transparency   expressed in bytes should be converted to RGBA images
  'to RGBA images')

[QuLogic]

Actually, that's a pretty good hint... Use img_tiles.GoogleTiles(desired_tile_form='RGBA', style='only_streets') and it works correctly.

Not so sure if this qualifies as a bug so much as maybe an enhancement that could be made to automatically pick this setting?

[mattijn]

Ah, Yes! That makes sense, or maybe a comment in the function description would do.

[pelson]

Ah, Yes! That makes sense, or maybe a comment in the function description would do.

Would you be interested in contributing @mattijn? Docs are always a healthy thing to improve!

[pelson]

Action: change the default from RGB to RGBA. The implication is on performance only, AFAICS.

[enorazza]

This is also important for the Stamen class.
Try: cimgt.Stamen(style='toner-labels')
Output has black background :(
I haven't understood if there is a workaround for this.. where should I put the "desired_tile_form='RGBA'" parameter?

[enorazza]

Found the workaround!
This wasn't working: labels = cimgt.Stamen(style='toner-labels', desired_tile_form='RGBA')
But this does: labels = cimgt.GoogleTiles(url="http://tile.stamen.com/toner-labels/{z}/{x}/{y}.png", desired_tile_form='RGBA')
This needs to be added too: ax1.background_patch.set_visible(False)
After this: ax1 = plt.axes([0, 0, 1, 1], projection=labels.crs)