| TileStache.Goodies.Providers.Composite | index |
Layered, composite rendering for TileStache.
NOTE: This code is currently in heavy progress. I'm finishing the addition
of the new JSON style of layer configuration, while the original XML form
is *deprecated* and will be removed in the future TileStache 2.0.
The Composite Provider provides a Photoshop-like rendering pipeline, making it
possible to use the output of other configured tile layers as layers or masks
to create a combined output. Composite is modeled on Lars Ahlzen's TopOSM.
The "stack" configuration parameter describes a layer or stack of layers that
can be combined to create output. A simple stack that merely outputs a single
color orange tile looks like this:
{"color" "#ff9900"}
Other layers in the current TileStache configuration can be reference by name,
as in this example stack that simply echoes another layer:
{"src": "layer-name"}
Layers can be limited to appear at certain zoom levels, given either as a range
or as a single number:
{"src": "layer-name", "zoom": "12"}
{"src": "layer-name", "zoom": "12-18"}
Layers can also be used as masks, as in this example that uses one layer
to mask another layer:
{"mask": "layer-name", "src": "other-layer"}
Many combinations of "src", "mask", and "color" can be used together, but it's
an error to provide all three.
Layers can be combined through the use of opacity and blend modes. Opacity is
specified as a value from 0.0-1.0, and blend mode is specified as a string.
This example layer is blended using the "hard light" mode at 50% opacity:
{"src": "hillshading", "mode": "hard light", "opacity": 0.5}
Currently-supported blend modes include "screen", "multiply", "linear light",
and "hard light".
Layers can also be affected by adjustments. Adjustments are specified as an
array of names and parameters. This example layer has been slightly darkened
using the "curves" adjustment, moving the input value of 181 (light gray)
to 50% gray while leaving black and white alone:
{"src": "hillshading", "adjustments": [ ["curves", [0, 181, 255]] ]}
Available adjustments:
"threshold" - apply_threshold_adjustment()
"curves" - apply_curves_adjustment()
"curves2" - apply_curves2_adjustment()
Finally, the stacking feature allows layers to combined in more complex ways.
This example stack combines a background color and foreground layer:
[
{"color": "#ff9900"},
{"src": "layer-name"}
]
Stacks can be nested as well, such as this combination of two background layers
and two foreground layers:
[
[
{"color"" "#0066ff"},
{"src": "continents"}
],
[
{"src": "streets"},
{"src": "labels"}
]
]
A complete example configuration might look like this:
{
"cache":
{
"name": "Test"
},
"layers":
{
"base":
{
"provider": {"name": "mapnik", "mapfile": "mapnik-base.xml"}
},
"halos":
{
"provider": {"name": "mapnik", "mapfile": "mapnik-halos.xml"},
"metatile": {"buffer": 128}
},
"outlines":
{
"provider": {"name": "mapnik", "mapfile": "mapnik-outlines.xml"},
"metatile": {"buffer": 16}
},
"streets":
{
"provider": {"name": "mapnik", "mapfile": "mapnik-streets.xml"},
"metatile": {"buffer": 128}
},
"composite":
{
"provider":
{
"class": "TileStache.Goodies.Providers.Composite:Provider",
"kwargs":
{
"stack":
[
{"src": "base"},
[
{"src": "outlines", "mask": "halos"},
{"src": "streets"}
]
]
}
}
}
}
}
It's also possible to provide an equivalent "stackfile" argument that refers to
an XML file, but this feature is *deprecated* and will be removed in the future
release of TileStache 2.0.
Corresponding example stackfile XML:
<?xml version="1.0"?>
<stack>
<layer src="base" />
<stack>
<layer src="outlines">
<mask src="halos" />
</layer>
<layer src="streets" />
</stack>
</stack>
Note that each layer in this file refers to a TileStache layer by name.
This complete example can be found in the included examples directory.
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