Glacier labels color and thresholds

[imagico]

fixes #1016

• changes the glacier label color to mix(darken(@glacier, 40%), darken(@glacier-line, 30%), 50%).
• changes the airport label color and icon to a violet tone to be better distinguishable from both glacier and waterbody labels.
• changes the size threshold for showing labels to be closer to as it was before. There are still significantly less labels at z=10 but better than before (where at z=10 almost no mountain glaciers showed up).
• adds an additional rule for showing very large glaciers (>10000 pixel) already at z=8. Due to the size distribution of actual glaciers this only affects larger icefields and icecaps, only a handful of them outside the polar circles (a few in Iceland, two in Norway, two in Patagonia and a few mostly unnamed ones in Alaska/Canada).

[matkoniecz]

Can you rebase this branch? For example imagico@220d840 is later reverted (compare overall diff: https://github.com/gravitystorm/openstreetmap-carto/pull/1031/files ).

[matkoniecz]

Also, https://github.com/gravitystorm/openstreetmap-carto/blob/master/symbols/helipad.p.16.png (and maybe other symbols) should also change color to keep this proposal consistent.

[imagico]

Regarding rebase - i tried and it would not let me so i merged the later changes. I am sorry if this is not correct - i am not that fluent with git.

I saw the helipad icon but there are many icons at the high zoom levels with this color (parking, bus station, lighthouse etc.) and changing only the helipad one would be kind of strange. The airport icon OTOH is is only shown at z=10 (the only icon use at these low zooms i think). Therefore i only changed this.

[matkoniecz]

Icons of the same type have the same colour. The question is whatever helipad is in the same group as airport (aerial transportation) or in the same bus as bus stop etc (minor transport).

IMHO the first categorization makes more sense.

Rebase is explained at (for example) http://git-scm.com/book/ch3-6.html (but it is possible for somebody else to resubmit these changes in a new PR, for example I may do it).

[imagico]

OK - commit history should be clean now.

The airport label changes will be done separately.

[matthijsmelissen]

Thanks. Personally I think the new rendering has too many names. I like the rendering where the names appear a zoomlevel later better. See the original area. Note that on z11, not all labels appear because they are pushed away by the mountains, which is something that needs to be looked at separately.

As I said before, the new colour is much better,

[imagico]

Well - this is a matter of taste and priorities of course. I checked various glacier areas around the globe and i think the 750 pixel threshold is a reasonable compromise, previously at z=10 there were much more labels already, in the Alps the size threshold usually was often not really the limit because the labels mostly blocked each other, at z=11 there were only a few more based on feature size (about the same as with this change i think - unless other features like peaks block the labels of course) and at z=12 all of them (now gradually increased until 17).

[matthijsmelissen]

Assigned to @gravitystorm for review.

[matkoniecz]

@imagico - can you consider making a separate request for label color? I would merge it (there is no opposition to it, IMHO it is clearly better).

I am unsure about zoom levels - I am not opposing but I do not feel confident enough to merge this change.

[imagico]

For the size limits this change is a compromise between the original glacier labeling and how it is handled after the general labeling change in #941. I respect the opinion from @math1985 that he prefers the version with less labels but no arguments in that direction have been made so far.

With the current labeling settings labels formally start at z=10 but effectively no glacier labels are shown in the Alps, Caucasus, the contiguous US and the Andes north of Patagonia and only a handful for the Himalayas (mostly where mapping is not very detailed) at that scale.

And I do not remember any complaints about too many glacier labels before - and there were significantly more than even with this change.

If there are arguments for less labels i would be eager to hear, otherwise i think this change in thresholds is an improvement and would like to see it in the map.

[matthijsmelissen]

I have merged this as is. As far as I'm concerned we can consider fine-tuning later. Thanks @imagico!

[imagico]

Thanks - and as said, if there are situations were less labels would be better i would be happy to look at them.