mirror of
https://github.com/tumic0/QtPBFImagePlugin.git
synced 2024-11-27 21:24:48 +01:00
88 lines
3.3 KiB
Markdown
88 lines
3.3 KiB
Markdown
# QtPBFImagePlugin
|
|
Qt image plugin for displaying Mapbox vector tiles
|
|
|
|
## Description
|
|
QtPBFImagePlugin is a Qt image plugin that enables applications capable of
|
|
displaying raster MBTiles maps or raster XYZ online maps to also display PBF
|
|
vector tiles without (almost, see usage) any application modifications.
|
|
|
|
Standard Mapbox GL Styles are used for styling the maps. Most relevant style
|
|
features used by [Maputnik](http://editor.openmaptiles.org) are supported.
|
|
The style is loaded from the
|
|
[$AppDataLocation](http://doc.qt.io/qt-5/qstandardpaths.html)/style/style.json
|
|
file on plugin load. If the style uses a sprite, the sprite JSON file must
|
|
be named sprite.json and the sprite image sprite.png and both files must be
|
|
placed in the same directory as the style itself. A default fallback style
|
|
(OSM-Liberty) for OpenMapTiles is part of the plugin.
|
|
|
|
"Plain" PBF files as well as gzip compressed files (as used in MBTiles) are
|
|
supported by the plugin.
|
|
|
|
## Usage
|
|
Due to a major design flaw in the Mapbox vector tiles specification - the zoom
|
|
is not part of the PBF data - the plugin can not be used "as is", but passing
|
|
the zoom level is necessary. This is done by exploiting the optional *format*
|
|
parameter of the QImage constructor or the QImage::fromData() or
|
|
QPixmap::loadFromData() functions. The zoom number is passed as ASCII string
|
|
to the functions:
|
|
```cpp
|
|
QPixmap pm;
|
|
pm.loadFromData(tileData, QString::number(zoom).toLatin1());
|
|
```
|
|
The plugin supports vector scaling using QImageReader's setScaledSize() method,
|
|
so when used like in the following example:
|
|
```cpp
|
|
QImageReader reader(file, QString::number(zoom).toLatin1());
|
|
reader.setScaledSize(QSize(512, 512));
|
|
reader.read(&image);
|
|
```
|
|
you will get 512x512px tiles with a pixel ratio of 2 (= HiDPI tiles).
|
|
|
|
## Build
|
|
### Requirements
|
|
* Qt 5
|
|
* Google Protocol Buffers (protobuf-lite)
|
|
* Zlib
|
|
|
|
### Build steps
|
|
#### Linux
|
|
```shell
|
|
qmake pbfplugin.pro
|
|
make
|
|
```
|
|
#### Windows
|
|
```shell
|
|
qmake PROTOBUF=path/to/protobuf ZLIB=path/to/zlib pbfplugin.pro
|
|
nmake
|
|
```
|
|
#### OS X
|
|
```shell
|
|
qmake PROTOBUF=path/to/protobuf pbfplugin.pro
|
|
make
|
|
```
|
|
|
|
## Install
|
|
Copy the plugin to the system Qt image plugins path to make it work. You may
|
|
also set the QT_PLUGIN_PATH system variable before starting the application.
|
|
|
|
## Limitations
|
|
Text PBF features must have a unique id (OpenMapTiles >= v3.7) for the text layout
|
|
algorithm to work properly.
|
|
|
|
## Status
|
|
A picture is worth a thousand words. Data and styles from https://openmaptiles.org.
|
|
#### OSM-liberty
|
|
|
|
|
|
|
|
|
|
|
|
|
|
#### Klokantech-basic
|
|
|
|
|
|
|
|
|
|
|
|
|