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1 | <?xml version="1.0"?> | |
2 | <!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" | |
4 | [ | |
5 | <!ENTITY appname "Viking"> | |
6 | ] | |
7 | > | |
8 | <section id="MapnikRendering" xreflabel="Mapnik Rendering"> | |
9 | <title>Mapnik Rendering Layer</title> | |
10 | ||
11 | <para> | |
12 | The Mapnik Rendering Layer uses the <ulink url="http://mapnik.org/">Mapnik Library</ulink> to generate map images according to the Mapnik configuration. | |
13 | </para> | |
14 | ||
15 | <para> | |
16 | When using this layer it is useful to review the <xref linkend="prefs_mapnik"/> to ensure the settings are correct for your system. | |
17 | </para> | |
18 | ||
19 | <para> | |
20 | Mapnik configurations can be created via the CartoCSS Mapnik stylesheet pre-processor. | |
21 | &appname; will automatically invoke the <emphasis>carto</emphasis> program when a carto project file is specified. | |
22 | Currently &appname; can not tell when an included file of the project has changed, so there is an option to manually run the carto command. | |
23 | </para> | |
24 | ||
25 | <para> | |
26 | &appname; will only (re)render tiles when it believes it is necessary - such as when there is no tile in the file cache, | |
27 | when there is a new Mapnik configuration style or the tile is over a certain age. | |
28 | To force &appname; to (re)render all tiles - create the file <filename>~/.viking/planet-import-complete</filename> | |
29 | and/or update its timestamp. (e.g. using the <emphasis>touch</emphasis> command). | |
30 | </para> | |
31 | ||
32 | <para> | |
33 | Creating a Carto project or an initial Mapnik configuration file and maintaining the datasource is beyond the scope of this documentation. | |
34 | There are various existing Carto projects such as <ulink url="https://github.com/gravitystorm/openstreetmap-carto">OSM Carto</ulink> | |
35 | or <ulink url="https://github.com/mapbox/osm-bright">OSM Bright</ulink>. These use OSM data and contain guides on how to setup the datasource. | |
36 | Further detail about using OSM data can be found on the <ulink url="http://switch2osm.org/loading-osm-data/">Switch2OSM</ulink> website. | |
37 | </para> | |
38 | ||
39 | <para> | |
40 | If you use a simple Mapnik configuration then the tile rendering time can be negligible and you can avoid having a tile cache. | |
41 | However for most systems using a stylesheet of similar complexity to the OSM Carto styling, | |
42 | rendering a tile (including reading/acquiring the data) can take some time and thus several seconds to generate a display screen's worth of tiles. | |
43 | Hence &appname; runs these tasks in the background and uses the tile cache to save this output. | |
44 | </para> | |
45 | ||
46 | <para> | |
47 | Generated tiles are stored in the <emphasis>PNG</emphasis> format in the standard <ulink url="http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames">OSM Tile name</ulink> layout. | |
48 | </para> | |
49 | ||
50 | <note> | |
51 | <para> | |
52 | Currently due to code build and dependency complexities, Mapnik Rendering is not available in the <trademark>Windows</trademark> version of &appname; | |
53 | </para> | |
54 | </note> | |
55 | ||
56 | <section><title>Layer Properties</title> | |
57 | <para> | |
58 | Configurable properties: | |
59 | </para> | |
60 | <formalpara><title>Carto project file</title> | |
61 | <para>When specified, this is used to generate the mapnik configuration file.</para> | |
62 | </formalpara> | |
63 | <formalpara><title>Mapnik configuration file</title> | |
64 | <para>Specify the Mapnik configuration file or leave it blank when using a Carto project file.</para> | |
65 | </formalpara> | |
66 | <formalpara><title>Alpha</title> | |
67 | <para>Control the Alpha value for transparency effects using a value between 0 and 255 with the default being 255 for a fully solid image, whereas 0 is transparent.</para> | |
68 | </formalpara> | |
69 | <formalpara><title>Use File Cache</title> | |
70 | <para>The default is to use a file cache.</para> | |
71 | </formalpara> | |
72 | <formalpara><title>Tile cache directory</title> | |
73 | <para>The top level directory of where the generated tiles are stored.</para> | |
74 | </formalpara> | |
75 | </section> | |
76 | ||
77 | <section><title>Layer Operations</title> | |
78 | <para>These extra options are available when right clicking on the Mapnik Rendering Layer in the Layers Panel.</para> | |
79 | <formalpara><title>Refresh</title> | |
80 | <para>Reload the Mapnik configuration.</para> | |
81 | </formalpara> | |
82 | <formalpara><title>Run Carto Command</title> | |
83 | <para>Force running the carto command and reload the generated Mapnik configuration.</para> | |
84 | </formalpara> | |
85 | <formalpara><title>About</title> | |
86 | <para>Show some information about the Mapnik version in use.</para> | |
87 | </formalpara> | |
88 | </section> | |
89 | ||
90 | <section><title>Viewport Tools</title> | |
91 | <para> | |
92 | When a Mapnik Rendering Layer is selected in the Layers Panel, the <guilabel>Mapnik Features</guilabel> tool can be selected from the toolbar. | |
93 | This enables location dependent actions to be invoked by right clicking on the viewport and selecting an action from the drop down menu. | |
94 | </para> | |
95 | <itemizedlist> | |
96 | <listitem> | |
97 | <para>Rerender Tile.</para> | |
98 | </listitem> | |
99 | <listitem> | |
100 | <para>Tile Info</para> | |
101 | </listitem> | |
102 | </itemizedlist> | |
103 | </section> | |
104 | ||
105 | </section> |