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Here is an example of adding customization code to the script. I used the Outdoor theme from locus store which works with v3 maps because it is a very small and simple theme (only 1400 lines).

In the customisation section of the script is uses the keys and values of rules in the theme to isolate and apply specific modifications to certain tags and their attributes, e.g.:

      if inscope(current_keys, "highway") then
         if current(current_vals) = "motorway_junction" then
            if current_tag = "circle" then
               line = update_tag(line, "r", 1.5, 0)
               line = update_tag(line, "stroke-width", 2, 0)
            end if
            if current_tag = "caption" then
               line = update_tag(line, "font-size", 1, 3)
               if instr(line,"caption k="+Chr(34)+"addr:housenumber"+Chr(34)) > 0 then
                  line = update_tag(line, "dy", 0, 0)
               end if
            end if
         end if
      end if

This looks for lines of the theme that are in scope of k="highway" v="motorway_junction" and then tweaks:
   - the circle's radius and stroke-width
   - its caption's  font-size and dy offset (but only for addr:housenumbers captions).

Here is the theme content before from v3:

<!-- highway exits -->
<rule e="node" k="highway" v="motorway_junction" zoom-min="11" zoom-max="13">
   <circle r="6" scale-radius="false" fill="#dFdFFF" stroke="#FF0000" stroke-width="2.0"/>
</rule>
<rule e="node" k="highway" v="motorway_junction" zoom-min="14">
   <circle r="6" scale-radius="true" fill="#dFdFFF" stroke="#FF0000" stroke-width="1.2"/>
   <caption k="addr:housenumber" display="always" dx="-2" dy="10" priority="95" font-style="bold" font-size="6dp" fill="#FF0000" stroke="#FFFF00" stroke-width="1.2dp" scale-font-size="14,1.3"/>
   <caption k="name" display="always" dy="-14dp" scale-dy-size="16,1.2" font-style="bold" font-size="7dp" fill="#0100C8" stroke="#FFFFFF" stroke-width="1.2dp" scale-font-size="14,1.3"/>
</rule>

and after in the converted v4 version:

<!-- highway exits -->
<rule e="node" k="highway" v="motorway_junction" zoom-min="10" zoom-max="12">
   <circle r="2.7" scale-radius="false" fill="#dFdFFF" stroke="#FF0000" stroke-width="0.9"/>
</rule>
<rule e="node" k="highway" v="motorway_junction" zoom-min="13">
   <circle r="2.7" scale-radius="true" fill="#dFdFFF" stroke="#FF0000" stroke-width="0.54"/>
   <caption k="addr:housenumber" display="always" dy="0" priority="95" font-style="bold" font-size="9" fill="#FF0000" stroke="#FFFF00" stroke-width="1.08" />
   <caption k="name" display="always" dy="-14" font-style="bold" font-size="10" fill="#0100C8" stroke="#FFFFFF" stroke-width="1.08" />
</rule>

I should point out that the stroke-width of circles also have a scale of 0.9 and 0.25 applied to it elsewhere in the script, hence 2 * 0.9 * 0.25 * 2 = 0.9. As you can guess, I was just applying correction by trial error until things looked reasonable...

Note the parameters for update_tag are:
   - update_tag( line, tag_name, scale, offset )
and it applies a scale and offset to numerical tag values. E.g. The following line:

         line = update_tag(line, "font-size", 2, -4)

when applied to the following theme line:

   <pathText k="name" font-style="bold" font-size="9" fill="#606060" stroke="#ffffff" stroke-width="2.0"/>

will result in the font-size being processed as:  new-font-size = (old-font-size * 2) - 4 = 14. i.e.:

   <pathText k="name" font-style="bold" font-size="14" fill="#606060" stroke="#ffffff" stroke-width="2.0"/>.

The script has a variable called "zoom_offset" which is set to -1 in this example. It subtracts 1 from all the zoom-min and zoom-max values to readjust the v4 converted theme to look similar in scales as the original v3 theme. Of course, if there are map elements that appear at zoom level 14, the will not appear at zoom level 13 in the v4 map.

The screenshots show the original v3 Outdoor theme, converted to v4 theme and the original OutdoorV4 theme.



I'm posting the converted outdoor theme only as an example of what the script can do. I haven't checked it extensively and you are probably better off using the official OutdoorV4 theme.

Attached is the Waymark-V2a theme in two forms:
   - Waymark-V4.xml is converted using the attached version of the v3_to_v4_Waymark.vbs script.
   - Waymark-V4a.xml is after some manual tweaks, read on...

the V4 of the theme is straight out of the script from V2a, with just one customisation to correct a syntax error:

      line = replace_text(line, "case="+Chr(34), "cat="+Chr(34) )

In the screenshots you can see that V4 has a rendering problem with service|raceway roads. I fixed this manually in V4a.



The script pseudo-converts the v3 extensions for rectangle captions using a thick outlined caption, as these are not supported in v4 mapsforge rendering engine.

The other thing you'll notice is when you switch to a v4 map the zoom level is out by 1, and you can see that some items that render at Z16, do not render at Z15, hence screenshot 4 shows them appearing as you zoom in to Z16.

Note that I have not checked if everything else in the theme works or not. But it probably is a good starting point now for getting a v4 map version of the Waymark-V2a theme working, if required.

At the moment I'm converting my OS Map theme from v3 to v4. I have been finding the process very mechanical and repetitive, so much so that once I I done around 2,500 lines out of 10,000 lines by hand I decided to quick put together a script to do most of the changes programatically. 

Attached is a VBScipt that does most of the changes required to convert a v3 theme to v4.

I quickly discovered that  v4 render engine is very intolerant to syntax errors and if any are present it will refuse to display anything. This means manually removing parts of the generated v4 theme until it works and locating the syntax error. The following are some examples of errors I found in several themes:
   - stroke-width="1.2p"
   - <rule case="off_pl"
   - close="yes"  (should be closed="yes")

I have converted the following themes using the script, in some cases requiring some additional custom mods:
   - OS Map
   - Outdoor (because it is small, simple and already has a v4 theme to compare with)
   - Waymark2a

I would consider the output of the script as a starting point only and not a final theme. In some cases it is possible to tweak the theme using the script, see the Outdoor script for an example. In some cases there are differences that have to manually changed in the generated theme. Waymark2a is an example of this, seems the v4 rendering in LoMaps has a bug, the following puts green dashes on service roads as well as raceways:

<rule e="way" k="highway" v="service|raceway" zoom-min="14">
   <line stroke="#ffffff" stroke-width="0.81" />
   <rule e="way" k="highway" v="raceway" zoom-min="14">
      <line stroke="#a5cba5" stroke-width="0.54" scale="all" stroke-dasharray="1,1" stroke-linecap="butt" />
   </rule>
   :

so I had to manually separate service and raceway rules to fix this:

<!-- service raceway -->
<rule e="way" k="highway" v="service" zoom-min="14">
   <line stroke="#ffffff" stroke-width="0.81" />
   :
<rule e="way" k="highway" v="raceway" zoom-min="14">
   <line stroke="#ffffff" stroke-width="0.81" />
   <line stroke="#a5cba5" stroke-width="0.54" scale="all" stroke-dasharray="1,1" stroke-linecap="butt" />
   :


I'll add the converted Outdoor and Waymark example themes in the next few posts. I'm using the initial conversion of my OS Map theme as a starting point for a v4 OS Map theme. I'm about 50% complete so far, but am battling with lack of symbol and text scaling in v4...

Please note that this script is a quick hack, there are probably better ways using XML libraries to do this... It does no error checking and you'll probably need to modify it for best results. It is a visual basic script and should work on a Windows command line using the following command line syntax:

     cscript v3_to_v4.vbs <v3 rendertheme>.xml <v4 rendertheme>.xml

Where:

        v3_to_v4.vbs                 -- Name of this script
        <v3 rendertheme>.xml         -- Input file that is a v3 rendertheme file, e.g. VoluntaryV3.xml
        <v4 rendertheme>.xml         -- Output file to be created as a v4 rendertheme file, e.g. VoluntaryV4.xml


Just putting this out there in case it is useful to other theme writers. It isn't really suitable for most people to use, but anyone with a basic understanding of visual basic and renderthemes should be OK.
I would check the examples in the following posts for examples of how to use the custom coding section and supporting functions...

Karl.

I will look into borders. I have mainly focused on UK usage and put in support for borders on admin_levels of 4=country, 6=county, 8=districts and 10=parish. However, it seems the UK maps only support country borders....

I updated the theme to include admin levels 2 and 3 together with existing used level 4 to the country borders, this seems to work. I hope this is the correct interpretation of admin levels...

But I think it would better to use an extra option for hiding, because I want see land access (without restricted area)
And....I have realize that you forget to show borders :-)

Land access is shown separately from restricted areas, see attached which shows the two areas overlapping.

I will look into borders. I have mainly focused on UK usage and put in support for borders on admin_levels of 4=country, 6=county, 8=districts and 10=parish. However, it seems the UK maps only support country borders.... Perhaps if I got this wrong someone can hint what the correct mappings of admin_levels should be... perhaps some of the unused levels are used in other maps...?

The "purple markers" are to highlight or emphasise protected areas that might have restricted access. In the UK they seem to match quite closely the OS map land access areas.

You can deselect them in the overlay options of the theme by unticking "emphasise land access".

I've started porting the theme into a version for v4 maps. It is going well so far, I am transferring section by section.  However, the OS Map theme makes extensive use of many v3 locus extended rendering options that are not supported in v4, so i do not think the v4 version will be as good as the v3 version.  Missing the ability for dash arrays to scale up as you zoom in. This will affect a lot of the theme elements that make it similar to OS maps.

By my older stats, it was about 60-70% users use LoMaps (V3), rest use combination of OpenAndroMaps (mainly) + some others.

Appreciate your work, looks pretty nice! If you would be interested to put it into Locus Store for direct download over the app, just let me know, @voldapet will help with it.

Thanks Menion for the positive feedback. I have been delaying posting the theme for a while because there is always something additional to add. In fact on my list of things I really want to fix are:
   - Toll roads not as per OS yet.
   - Airport runways at 1:50k not same as OS.

I am more than happy to include the theme in the Locus Store. I thought it makes sense to see what the "early testers" find and fix first... Is there much involved in making it ready for direct download?

The accentuation will be felt on all cycle routes, not just on roads specially built for cyclists.

Hi Žajdlík Josef, which theme are you using that highlights cycle routes differently for roads vs off-road routes?  I was trying to figure out a way to differentiate between them because OS maps use a different symbol for non-traffic routes, but I couldn't figure out any way of doing it.

Having said that, in your example the cycle track is not on the road... so perhaps it is just the surface type...   The highlighting scheme was kept from the original Voluntary UK theme...
Karl.

For me I am also missing the names of the hiking trails like E3 and GR5.
And also please put a .nomedia  file in your directories otherwise my Gallery App is flooded. 

I've replaced the theme with an updated version that now contains .nomedia files. I had them in there originally, but got over zealous deleting unused files before posting.

The hiking trails by default do not display their name labels (CW) but rather their full textual names (Cotswold Way). This is to be as compliant with Ordnance Survey's own maps. I have noticed that most non-LoMaps do not support this full name text of hiking trails, so I have included support for displaying the hiking trail labels, these are enabled by selecting the overlay "non-OS symbols" - you'll see in the Legends that all the non-OS symbols have a little 'cross' symbol next to them and a foot-note that tells you which overlay option selects them.

Hope that helps, Karl.

Hmm... I'm now wondering if I am actually using v3 maps after all... You are correct, all the v4 maps I tried do not work with OS Map theme.... I've started to look into it, seems v4 maps are handled differently in Locus Map from v3. I looked at how Velocity works for v3 and v4 and I got OS Map to be selectable for v4 maps but it displays nothing so far, seems I need would need create a new theme for v4 maps using different scalings/sizes etc... quite a bit of work.  Note Velocity is supporting v4 with a completely different theme with the same name...

For now I would suggest that this theme is for v3 maps only (I changed the post's title to reflect this too). I will look to see if I can get a v4 version working, but I suspect this may take some time. If anyone has any tips of converting v3 theme to v4 theme I would be glad to hear. Seems the zoom levels are reduced by 2 and line thicknesses are narrower and not using "dp" values...

Update: Found this might be useful: http://www.maiwolf.de/locus/
Update: Also found: https://www.openandromaps.org/en/oam-forums/topic/mapsforge-rendertheme-reference

Karl.

I would love to test it but it seems not compatible with the V4 ML maps from openandromaps.org that I mostly use.

Hi Henk, I thought I am using it with all the UK v4 OAM maps without issue (but I think I have v3 maps). Can you provide me link to the download for the map you can't use?
Thanks Karl

Having used UK Ordnance Survey (OS) maps all my life, when I started using Locus Map I was desperate for a map theme that looked similar. After using both Voluntary UK and OS Style themes for a while, I still hankered after something closer to the style of the original UK OS maps. So I decided to create my own theme that tries to emulate the Ordnance Survey 1:25k and 1:50k map styles as closely as is possible within the constraints of Locus Map and data provided by the vector maps. It should work with both LoMap and OAM maps. I must give credit to John Campbell for his Voluntary UK theme that I used as a starting point (v. 190101).

There are 6 maps styles provided in the theme:

• Explorer 1:25k
• Landranger 1:50k
• Dynamic Scale
• Night Mode 1:25k
• Night Mode 1:50k
• Night Mode Dynamic

Dynamic Scale automatically switches from 50k to 25k at zoom level 16.
Night Modes provide a darker colour scheme for night usage that preserve the OS colour, but muted a bit. I don't like the built in night mode as it inverts all the colours.

There are also several overlay options:

• non-OS  symbols
• non-OS road furniture
• demanding paths
• hiking routes, national
• hiking routes, local
• emphasise hiking routes
• cycling routes, national
• cycling routes, local
• emphasise cycle routes
• fill in residential areas
• grow 50k buildings into town masses
• emphasise land access
• OS style road labels
• level road labels
• boxed road labels

I used google translate to define the translations, so let me know if there are more appropriate translations.

I also created PDF legends for the 25k and 50k themes to show what is supported/different using a similar style to the original OS legends with screenshots from Locus Map and the theme's own symbols etc.

Last attachment is a ZIP of the theme. (now with .nomedia files, thanks Henk van der Spek for pointing that out).

Install in the usual way of unzipping in Locus Map's _theme folder, e.g.:

\<root>\Android\data\menion.android.locus.pro\files\Locus\mapsVector\_themes

I've only tried this on my phone (Samsung Galaxy A3) and tablet (Samsung Galaxy Note 10.1 2014). It is quite a big theme file now (~10,000 lines)  because it contains so many different categories and overlay options. I am interested to know if it works OK for everyone. I have considered creating a "lite" 25k only option to see it is works faster or not...

I am putting this theme out there as I feel it might be of interest to others. It is provided as is.
I am not inclined to spend a lot of time working on it, but you are welcome to modify it for your own purposes.

Let me know if there some major problems with the theme.

Here is a comparison of the same map rendered with: Internal Theme, Voluntary UK, OS Style and my new 4 OS map styles (also attached as ThemePreviews_LORES.jpg but lower resolution):


USE SCROLL BAR TO VIEW THE REST >>>>

UPDATE 2020.04.27
I have fixed:
   - couple of  mistakes in the legends
   - added to the legends some additional overlay footer notes.
   - country borders to include admin_levels 2, 3 and 4 now.
   - rounded locks in rivers now square
   - some syntax errors I found during porting to v4 (which is now about 50% completed).

I've updated the attachments with new versions, hence their counters are reset.