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Well -- I think I am giving up on OAM. Yes, their themes are excellent, but they do not render well in gray scale. My version of a B&W theme didn't work out of the box" I think that it is because I am using html color names -- black instead of #000000 -- which breaks rendering (!?). A brief experiment suggested that features rendering is also limited by the zoom level, so there isn't much room for improving my use case.

BTW -- I am able to reasonably see routing options between Uluru and Little Sandy Desert, which is good  enough for me

I'll eventually get back to this idea when I have more free time on my hands.

Thanks again for your input

Thanks for the nudge.

I've installed an OAM map. On the plus side, it looks as if features can be displayed at a smaller scale. Unfortunately the General/Element/Elevate themes do not render very well on an e-ink device and it is not clear how I can make my theme work. I've tried putting the xml file inside the _themes/Elevate folder, to no avail. I've also tried to replace the Elevate.xml with my theme and still no love.

I'll examine the Elevate and try to understand what breaks.

Will eventually update on this thread.

Thanks again

[ The question is whether it is even a good idea to render small road lines below level < 12. I think the number of roads would be large and the map would become unreadable.

I understand your point. However in parts of the world, there are few roads of any size, and small scale is all but necessary. Take Australia. Even on a large computer screen, using Google Maps, figuring out options to travel from Uluru to Little Sandy Desert without a routing software is all but impossible. In Locus, after quite a bit of zooming in/out in order to locate reasonable endpoints, bRouter will come up with a suggestion that you'll have to follow more or less blindly because there is no way to visualize alternatives.

Same issue in Northern Canada (where I live) and, I assume, the stans/Mongolia,. large portions of South America and Africa...

Anyhow -- I think it would be great if the map file didn't make rendering assumptions. I'll try to find the time to generate an agnostic map and see if there is any performance issue when these instructions are located in the theme.

Or may I tempt you in generating a map set for Australia (and Canada) and I'll let you know how things went on my cheap, yet beloved, e-ink phone?

I am familiar with Element. IIRC I've used it at some point in time.

Thing is, from what I understand, it cannot render a feature that isn't available (zoom-appear). Unless I am missing something, tertiary is unavailable at a zoom smaller than 12, track at 13, camp_site at 14 (or 12, not obvious) (source here https://github.com/asamm/mapsforge-v3-modded/blob/master/various/tag-mapping-xml/tag-mapping-tourist.xml). And Element will not render in black and white, which is why I got motivated to learn a thing or two about themes and stuff...

My understanding is that it would be possible to extract map data with every feature appearing at zoom 0, and to defer rendering at a given zoom level to the xml (theme) instructions. I don't know how to do this for now, and presume that it may take more than a rainy Sunday to figure out. Yes, there is pleasure in learning new stuff, but life being short, I'd hope to motivate others to do it for me.

[really]

Thanks for your time (and patience). I am new to this and ask questions left and right.

I am quite pleased with the latest iteration of hcLayers high contrast theme. It essentially does what I want with, perhaps, two caveats:

1. The display of place names is not working well. I've posted in a different sub-forum. The Paris/Argenteuil is just a more visible and funny quirk. I plan to (a) upload place names POIs in order to be able to improve rendering; or (b) download Stamen Toner tiles at small scale as a stop-gap measure.

2. I would really love to be able to display some features at any scale, determined by the theme rather than by the .map. In particular small roads (tertiary, unclassified, tracks, etc.) that are often the only type of "highways" in sparsely populated areas. (I'll try to learn how to generate custom maps, but life is short and perhaps you'll consider selling LoMaps+

Would it be possible to improve place name rendering?

Attached is a screen shot of France taken from the LoMaps city theme, compared to Stamen's toner (my device has a grayscale display).

Notice that the LoMap shows Argenteuil instead of Paris most likely because Argenteuil is rendered before Paris.

I have found my way of generating vector maps and even POIs (overwriting the .db file from LoPoints).

Could you expand on this? I would like to add POIs (rest areas).

I've just finished the first draft of a theme that I use on my e-ink phone. The xml and svg files are on gitHub https://github.com/gauvins2/mapThemes

Attached is a comparison of the stock Hike/Bike theme (left) and the hcLayers (right).

[Locus' engine renders all the tiles that are visible at a given zoom level]

@voldapet -- thanks for your pointers.

WRT community themes, there isn't much. The market for e-ink devices is very small. I am working on a grayscale theme, which already works quite well for my purposes.

Two things perhaps --

1. I use Locus in the field (bike touring) to generate routes if the need arises. A key element is the presence/absence of camp sites or such, so I've changed the theme to display camp/caravan POIs at the smallest scale possible. So far so good. However, when I've added picnic sites, which are far more numerous, rendering screeched to a halt.

My understanding is that Locus' engine renders all the tiles that are visible at a given zoom level. If the user figures that something is wrong with rendering and zooms in, in order to reduce the number of features to render, the engine will keep going on the previous task before computing the new set of tiles. Which is odd because unless I am wrong, changing the theme kills the current rendering operation and starts a new one.

2. A related question is what are the best practices for POIs icons. Looks like the source is an .svg that the engine scales to the right size, from which it creates a .png copy that is cached and used as needed. If the icons were always rendered at the same size, irrespective of the zoom-level, would it make sense to pre-render the icons (i.e. link to properly sized icons)?

Thanks for the pointer.

I will take a look at OAM. But to be honest, I'll probably stick with LoMaps because they work well and (I assume) support the team behind Locus.

I've edited the theme. Improves things in some cases (ex: campgrounds can be seen at a smaller scale than currently themed); but not for others (route planning in Northern Quebec is an adventure in zooming in-out).

I've sent a request to LoMaps (Assam). Might also try alternative maps - was hoping for a simpler solution

Thanks again for your time

Thanks for your input.

So I gather that it is not possible to change the .map hard=coded ZL values. Too bad.

Would you happen to know if it might be possible to ask for a different set of values for highway=tertiary|unclassified|cycleway ?

My understanding is that the zoom level at which a map feature is visible is determined by the map data and not by the theme that is applied to it. If I am wrong, please correct me. Otherwise, is it possible to edit the *.map or *.db in order to change the design setting?

This wiki entry suggests that small roads become visible at a zoom level of 15 or more https://wiki.openstreetmap.org/wiki/Zoom_levels. I'd like to be able to see them at a smaller scale. Idem for some POIs such as campsites.

I use an e-ink phone (Hisense A5) and would like a high contrast theme similar to Toner (https://openmaptiles.github.io/maptiler-toner-gl-style). The OSM theme definition can be found on GitHub https://github.com/stamen/toner-carto.

I know nothing about theme development. Could someone point me to useful resources? Ideally a walk-thru to convert an OSM theme to Locus. (or even better, a Locus port of the OSM theme )