cut an image into web map tiles
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readme.md

Tilesaw

Tiled Arch, Artist Unknown, Pakistan, 18th century

Builds off jcupitt/libvips and mapbox/mbutil to cut images into map tiles.

Components

tilesaw.sh

A shell script for cutting a large image into "map" tiles suitable for leaflet. It uses vips for the tiling, exiftool to ensure {width: …, height: …} exist in the resulting metadata.json, and mb-util to package the tiles as .mbtiles.

I've built my own vips that tiles images (z/x/y) (instead of (z/y/x)) and doesn't pad non-square tiles.

index.js

An express.js app that brokers (a) serving and (b) downloading and tiling new images, to then be served.

  • index.js takes the name of an image and checks whether it's been tiled yet. If it has (indicated by an affirmative response from tilestream, serve the tilejson for that image. If not, it attemts to download the full-res image and tile it.
  • tilestream serves tiles that have already been converted

The tilesaw server has two methods:

  • /: list all available, tiled images.
  • /:image: return tileJson for :image. If the image hasn't been tiled yet, attempt to retrieve it and process it into tiles.

The app uses 'adapters' to find images to tile. When tilesaw can't find tiles for an image, it will try each adapter to find a suitable image. If the adapter succeeds, it's responsible for tiling the image and indicating its success. If not, the next adapter gets a try.

Each adapter is a function(imageName, options, callback). The node callback style is function(err, data): if err is non-null, something went wrong. Otherwise that adapter found an image matching imageName and tiled it.

Example adapters:

  • adapters/noop.js doesn't do anything. It logs a message to the console and returns an error.
  • adapters/directory.js checks for a matching image in a predetermined directory. If one exists, it's tiled and passed back to the client.
  • adapters/mia-api.js pulls images from our API.

var adapters = '…' is a space-delimited list of adapters to try. If all the listed adapters fail, tilesaw will return a 404 with the error message from the latest adapter.

Installation

Ubuntu, by hand

It's not too tough to install by hand, but you have to know what you're doing.

First, install vips.

sudo apt-get update
sudo apt-get install build-essential gettext-base libglib2.0-dev libxml2-dev pkg-config pkg-config swig gtk-doc-tools automake gobject-introspection make libtiff-dev libjpeg-dev libpng-dev libexif-dev
git clone http://github.com/kjell/libvips.git
cd libvips
git checkout dzsave-zxy-no-padding
./bootstrap.sh
autoconf
./configure
make
sudo make install
export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH
echo 'export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH' >> ~/.profile

Test it with vips --version. If you see vips: error while loading shared libraries, that means vips can't find its shared libraries. This is most likely because LD_LIBRARY_PATH isn't set in your shell.

Next, install nodejs and python:

sudo apt-get install python-software-properties python python-setuptools g++ make
sudo add-apt-repository ppa:chris-lea/node.js
sudo apt-get update
sudo apt-get install libsqlite3-dev sqlite3 nodejs-dev npm libimage-exiftool-perl

Finally, install mb-util and tilesaw.

git clone https://github.com/mapbox/mbutil ~/tmp/mbutil
cd ~/tmp/mbutil
sudo python setup.py install

git clone https://github.com/artsmia/tilesaw ~/tmp/tilesaw
cd ~/tmp/tilesaw
npm install

Now you can start tilesaw (npm start).

By default it runs on port 8887, with tilestream on 8888. To run it you'll need to set a few environment variables:

environment variable default note
PORT 8887
IMAGEDIRECTORY ~/tmp/tilesaw/data/images the directory to look for untiled images
TILEDIR ~/Documents/MapBox/tiles Where to put the tiles
TILESAW ~/tmp/tilesaw Where is the tilesaw script?

Docker

So far the nodejs parts are should be easily replicable using Docker. If that's not your thing, the Dockerfile lays out what needs to happen to make everything work.

The vips installation isn't covered yet, that's coming soon.

Domain names

Then these servers should be reverse proxied by nginx to a subdomain. We're using tilesaw.dx.artsmia.org and tiles.dx.artsmia.org.