relet / setzkasten

A simple tiler to align high resolution images on an infinite zoomable plane.

setzkasten

A simple tiler to align high resolution images on an infinite zoomable plane. The results can be displayed with any regular mapping client that supports XYZ tiles.

The necessity for this approach evolved when I started taking (sometimes) gigapixel photos through focus stacking and stitching microscopy images. It is a self-hosted alternative to commercial operations like zoomify or easyzoom. In addition it allows you to arrange multiple images on the same plane. Currently this happens through the configuration files.

Self-hosting this type of map is made very affordable through static file CDN caching as for example provided by cloudflare.

An example viewer and configuration is provided.

Configuration

Configuration currently takes the form of a JSON file. The metadata is somewhat geared towards biological observations, but easy enough to change in the source code.

{
    "target": "/var/www/html/",
    "tilesize": 256,
    "maxzoom": 14,
    "sources": [
        ["filename.png", 65000, 210000, 18, "Title", "Family", "date", "location", "", "href"],
		...
}

Parameters:

• target: The image tiles will be generated into the folder target/tiles. A GeoJSON feature overview will be written to target/features.geojson.
• tilesize: The size of the cropped tiles.
• maxzoom: The maximum zoom level to generate. This can be set lower to generate faster previews.
• sources: An array with information about the image sources, in particular
  • Filename
  • Horizontal offset to the center of the plane (in pixels, relative to the specified zoom level. An image provided with a zoom level one lower will only use half of the pixels to be placed at the same location)
  • Vertical offset to the center of the plane
  • Zoom level, at which the image will be written with its full pixel extent. In lower zoom levels, the image will be scaled 50%, 25% etc. Higher zoom levels are currently not written, but simulated through the viewing client.
  • Title, etc.: Metadata that is written only to the GeoJSON file.

Each image in the sources array will be read in order. It will be split into tiles. Then for each tile, setzkasten will load an existing tile at this location (if it exists) and paste the tile data on top. Handling of transparency depends on the image formats.

Images late in the source array will be pasted over earlier images if they share the same location.

Finally, for all images, a GeoJSON file with image extents and metadata will be written to features.geojson. This file can be used to make the map more interactive.

Example

This is also the code behind my own (rather modest) entomological collection:

setzkasten.relet.net