|
|
|
[[Symbolizer|SymbologySupport]] that specifies rendering of an image from any [GDAL supported format](http://www.gdal.org/formats_list.html) using the [[GDAL]] plugin, from GeoTiff's using the [[Raster]] plugin or from PostGIS using the [[PgRaster]] plugin.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
* Mapnik supports on-the-fly reprojection of raster layers (like it does for vector layers)
|
|
|
|
* However, for optimal performance it can be best to first (externally) warp an image to the Spatial Reference System (srs) used in the map (e.g. using the `gdalwarp` command from the gdal-utilities).
|
|
|
|
|
|
|
|
* As of Mapnik 0.6.0 the RasterSymbolizer supports transparency and composition modes.
|
|
|
|
* See the original ticket for details: [#259](https://github.com/mapnik/mapnik/issues/259)
|
|
|
|
* See also [[Compositing]] for some of the effects.
|
|
|
|
|
|
|
|
* This Symbolizer is often used with DEM (digital elevation model) data containing missing values (for example NASA SRTM DEM data); to achieve nice rendering, the [gdal_fillnodata.py](http://www.gdal.org/gdal_fillnodata.html) tool might be useful.
|
|
|
|
|
|
|
|
* As of Mapnik 0.8 the RasterSymbolizer can be assigned a [[RasterColorizer]] to color a raw data raster according to a palette. This is useful for visualizing scientific data, dynamically changing the color gradient of a DEM, etc...
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Processed as described in http://wiki.openstreetmap.org/wiki/Hillshading_using_the_Alpha_Channel_of_an_Image
|
|
|
|
|
|
|
|
# Usage
|
|
|
|
|
|
|
|
| *parameter* | *value* | *description* |
|
|
|
|
|--------------|---------|-----------|
|
|
|
|
| opacity | 0.0 - 1.0 | 1 is fully opaque while zero is fully transparent and .5 would be 50% transparent |
|
|
|
|
| comp-op (previously called `mode` in <= Mapnik 2.0.x) | grain_merge, grain_merge2, multiply, multiply2, divide, divide2, screen, hard_light | Compositing/Merging effects with image below raster level (?). The formulas for combinding foreground (raster) and background are: grain_merge: bg + fg - 0.5, grain_merge2: bg + 2*fg - 1.0, multiply: fg * bg, multiply2: 2 * fg * bg, divide: bg / fg, divide2: 2*bg / fg, screen: (1-fg)*(1-bg), hardlight: see [[http://docs.gimp.org/en/gimp-concepts-layer-modes.html#id2834930]] |
|
|
|
|
| scaling | fast, bilinear, bilinear8 || fast: nearest neighbour, bilinear: bilinear interpolation for all 4 channels (RGBA), bilinear8 like bilinear, but only one channel assumed |
|
|
|
|
|
|
|
|
|
|
|
|
There are three types of raster datasources: *gdal*, *raster* or *pgraster*:
|
|
|
|
|
|
|
|
* The [[GDAL]] plugin is more convenient as it can read the file extents automatically and supports any GDAL-supported type of file
|
|
|
|
* The [[Raster]] driver only works with Tiled or Stripped GeoTIFF files and requires manually setting the file bounds, but can be faster.
|
|
|
|
* The [[PgRaster]] driver requires manually setting the band number to use as databand.
|
|
|
|
|
|
|
|
## XML Layers
|
|
|
|
|
|
|
|
See the [[GDAL]], [[Raster]] and [[PgRaster]] plugin pages for more info
|
|
|
|
|
|
|
|
|
|
|
|
## XML Styles
|
|
|
|
|
|
|
|
Default (simply renders a copy of the raster)
|
|
|
|
|
|
|
|
|
|
|
|
```xml
|
|
|
|
<Style name="My Style">
|
|
|
|
<Rule>
|
|
|
|
<RasterSymbolizer/>
|
|
|
|
</Rule>
|
|
|
|
</Style>
|
|
|
|
```
|
|
|
|
|
|
|
|
Using the new 0.6.0 release opacity / merging / scaling options:
|
|
|
|
|
|
|
|
```xml
|
|
|
|
|
|
|
|
<Style name="raster">
|
|
|
|
<Rule>
|
|
|
|
<RasterSymbolizer
|
|
|
|
opacity="0.5"
|
|
|
|
<!-- scaling="fast" -->
|
|
|
|
scaling="bilinear"
|
|
|
|
<!-- scaling="bilinear8" -->
|
|
|
|
|
|
|
|
<!-- mode="grain_merge" -->
|
|
|
|
<!-- mode="grain_merge2" -->
|
|
|
|
<!-- mode="multiply" -->
|
|
|
|
mode="multiply2"
|
|
|
|
<!-- mode="divide" -->
|
|
|
|
<!-- mode="divide2" -->
|
|
|
|
<!-- mode="screen" -->
|
|
|
|
<!-- mode="hard_light" -->
|
|
|
|
>
|
|
|
|
<!-- optional <RasterColorizer/> goes here -->
|
|
|
|
</RasterSymbolizer>
|
|
|
|
</Rule>
|
|
|
|
</Style>
|
|
|
|
```
|
|
|
|
|
|
|
|
## Python Styles
|
|
|
|
|
|
|
|
```python
|
|
|
|
s = Style()
|
|
|
|
r=Rule()
|
|
|
|
r.symbols.append(RasterSymbolizer())
|
|
|
|
s.rules.append(r)
|
|
|
|
```
|
|
|
|
|
|
|
|
## C++
|
|
|
|
|
|
|
|
` FIXME ` |
