[heatmap] Optionally use map as background

[laufhannes]

Depending on the heatmap's size, it may be nice to see at least some basic map in the background.

I have a first working solution with laufhannes@ebb0823 and laufhannes/staticmaplite@3758e11, but that's not perfect. The main part within this repo is to calculate lat/lng bounds of the visible part. Afterwards, a static map is requested, saved locally and inserted. (Without saving it locally, inkscape is not able to embed the image when converting to png)

The staticmaplite repo is written in php, but it should be possible to transform it into python. Using Google Maps Static may even be better (but requires an API key; in general free for non-commercial and low traffic apps), as it's possible to individually style the map. I created one first try for such a style at snazzy maps.

If using Google Maps, calculation of the required zoom level and cropping the image (or calculating the exact size) has to be done within this repo.

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As this testing has been done in my local runalyze-environment, the example is decorated with our brandings ;)

And I guess this needs some additional padding within the draw area to not let tracks touch the border.

[lefty01]

wow ... nice!

[flopp]

Very nice.

I already have some experience with static maps: https://github.com/flopp/go-staticmaps ;)

[lowtower]

@flopp @laufhannes

Hello,
are You interested in getting this done or has it been dropped for a reason?
Cheers,
LT

[flopp]

@lowtower it would still be nice to have this feature. One could certainly use https://github.com/flopp/py-staticmaps to generate the background image.

[lowtower]

I have already had a look at py-staticmaps (which btw. is also mentioned at the osm staticmaps website).
To be honest, I would prefer not to take it because it has pycairo as requirement, which is quite hard to install. I think it is quite a big obstacle for a lot of users (You need dev packages under linux) .
The approach of laufhannes to take the staticmaps provider and url directly as argument seems to be straight forward.
I'll try and make a pr when ready.

[lowtower]

btw:
I find the carto dark no labels tiles the best as background.
As far as I have seen they are yet not supported by py-staticmaps, right?

[flopp]

@lowtower you're right, cairo is heavy - i already thought about making it an optional dependency of py-staticmaps (e.g. use it only if it's available).

Anyway, I'm glad you're taking the initiative on this issue!

[lowtower]

@flopp
I have seen that You already have made cairo optional in py-staticmaps - so, I will try my best to use it instead of other options!

[flopp]

@lowtower I'm about to add a PIL-based renderer - this is more lightweight than Cairo, but has no anti-aliasing

[lowtower]

@flopp I have a first working version of the background staticmap feature.
You can have a look at my fork.
I have also forked the py-staticmaps project to add object independent boundaries.
At the moment there is no margin to respect the line width of the tracks, means that the tracks are some pixels wider than the background image.
Hope You like it nevertheless.
Cheers,
LT.

[flopp]

@lowtower the results look nice!

For a final version the background image should be embedded into the SVG (to have a single output file) I guess.

[lowtower]

Reminder to myself:
the copyright notice is also missing because it's cropped away - must be added again.

[lowtower]

Somehow, I feel like the cropping should be done in the py-staticmaps.
What do You think?

[flopp]

Hm, py-staticmaps should create the desired image size - so that no cropping is necessary in GpxTrackPoster.

[lowtower]

Maybe, I understood something fundamentally wrong.
I have to look over it again.