diff --git a/OutputFormats.md b/OutputFormats.md index d414477..8be1407 100644 --- a/OutputFormats.md +++ b/OutputFormats.md @@ -1,8 +1,3 @@ - - - - - # Mapnik Output Formats Mapnik supports rendering with both AGG and Cairo (see [[MapnikRenderers]] for more detail), and can create maps or map tiles in a variety of formats. @@ -44,8 +39,23 @@ So to use new format i.e. in python: or other example in c++: save_to_file(vw, "test.png", "png256:t=1:c=128"); -For more details see [mapnik-devel email](http://lists.berlios.de/pipermail/mapnik-devel/2010-March/001081.html and ticket [#477](https://github.com/mapnik/mapnik/issues/477) +## Hextree details +The m=h (hextree) method should give more smooth images in case of +transparent maps i.e. hybrid like overlayed on some satellite images. +Time and file size increase or decrease depends on content and image +size, but shouldn't be much in common situation. Octree is still the default +for png8 because for most maps without transparent +background or elevation colored/shaded rasters, existing method should +give acceptable and little bit smaller files. +With Hextree, using less than 64-94 colors is not recommended, because returned +palette isn't optimal then. Using 96-128 should give acceptable quality +with some file size reduction, but probably not more then 10%-20%. + +For more details see [mapnik-devel email](http://lists.berlios.de/pipermail/mapnik-devel/2010-March/001081.html) and ticket [#477](https://github.com/mapnik/mapnik/issues/477) + + +## render functions Most render functions like `save_to_string` also take a third argument which must be a `rgba_palette` object. You can create palettes by passing a buffer with RGBA values (4 bytes), a buffer with RGB values (3 bytes) or an Adobe Photoshop .act file (generated by the "Save for Web" dialog") with exactly 772 bytes to the `rgba_palette` constructors. Note that palette objects are mutable and contain a lookup table that cache all values ever retrieved for faster encoding.