Wetsaw is a library and command line application for rendering geographic tiles in the XYZ tile format. It is written in Python and builds on the Mapnik rendering library.

• Batched tile rendering: Multiple tiles are automatically rendered together in Mapnik for efficiency, then the tiles themselves are cut from the larger image
• Efficiently renders large tilesets: The library internally generates tile information as it is needed for rendering, allowing it to render millions of tiles in a consistent, small amount of memory
• Extent highlighting: (Optional) Generate a GeoJSON file that contains a world polygon with a hole matching the extent rendered
• Preserve old tiles: (Optional) Tile rendering can be run to fill in gaps rather than starting from scratch
• Watermarking: (Optional) Overlay a transparent png on all tiles. This image has a slight random offset within the tile to hinder automatic removal
• Status updates: (Optional) Communicate current rendering progress through a predefined file
• S3 file upload: (Optional) Publish the resulting tiles directly to Amazon S3
• WeoGeo preview data support: (Optional) Generate all of the preview data needed to upload to WeoGeo's servers

• Python (tested on 2.6.1+, not yet tested on 3.0)
• Mapnik (0.7.1 or 2.X)
• PIL (test on 1.1.7)
• boto (for s3 file upload)