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72 lines
2.8 KiB
Markdown
72 lines
2.8 KiB
Markdown
# QtPBFImagePlugin
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Qt image plugin for displaying Mapbox vector tiles
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## Description
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QtPBFImagePlugin is a Qt image plugin that enables applications capable of
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displaying raster MBTiles maps to also display PBF vector tiles without
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(almost, see usage) any application modifications.
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Standard Mapbox GL Styles are used for styling the maps. Most style features
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used by [Maputnik](http://editor.openmaptiles.org) are supported. The style
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is loaded from the
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[$AppDataLocation](http://doc.qt.io/qt-5/qstandardpaths.html)/style/style.json
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file on plugin load. A default fallback style (Klokantech-basic) for
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OpenMapTiles is part of the plugin.
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## Usage
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Due to a major design flaw in the Mapbox vector tiles specification - the zoom
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is not part of the PBF data - the plugin can not be used "as is", but passing
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the zoom level is necessary. This is done by exploiting the optional *format*
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parameter of the QImage constructor or the QImage::fromData() or
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QPixmap::loadFromData() functions. The zoom number is passed as ASCII string
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to the functions:
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```cpp
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QPixmap pm;
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pm.loadFromData(tileData, QString::number(zoom).toLatin1());
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```
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## Build
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### Requirements
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* Qt 5
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* Google Protocol Buffers (protobuf-lite)
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* Zlib
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### Build steps
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#### Linux
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```shell
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qmake pbfplugin.pro
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make
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```
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#### Windows
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```shell
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qmake PROTOBUF=path/to/protobuf ZLIB=path/to/zlib pbfplugin.pro
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nmake
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```
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## Install
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Copy the plugin to the system Qt image plugins path to make it work. You may
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also set the QT_PLUGIN_PATH system variable before starting the application.
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## Limitations
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As the plugin only has isolated info about a single tile image, texts
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overlapping to neighbour tiles can not be displayed or their overlapping can
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not be avoided (the plugin uses the first approach). This is a principal
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constraint that can't be evaded.
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## Status
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A picture is worth a thousand words. Data and styles from https://openmaptiles.org.
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#### OSM-liberty
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#### Klokantech-basic
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