Slice and dice an image, turning it into many equal sized tiles. Useful for tools like leaflet.js, to create interactive "slippy" maps.
The image is sliced up into equal sized tiles, based on the command line
option --tile-size (default 256 pixels).
Once the tiling is finished, the original is resized to half its current dimensions (the orignal file on disk is not touched) and the process repeats. Each halving is a new "zoom level".
Each file is named something like:
tile-z-x-y.png
Where 'z' is the zoom level, x and y are the coordinates, with 0,0 being the top left tile.
slicerdicer -help
slicerdicer -filename large_image.png -tile-size 256 -concurrency 5
The destination for the tiles can be changed with the -basename and
-path-template options. The path template must contain 5 placeholders,
in the following order:
%sbasename, as per-basename(defaulttile)%dzoom level%d'x' coordinate%d'y' coordinate%dfile format (jpg or png)
The default template is %s-%d-%d-%d.%s which results in a flat structure
with all files in the current directory.
For example, using -basename map and
-path-template '%s/zoom-%d/%d-%d.%s' will result in a file structure like:
map
├── 0
│ └── 0-0.png
├── 1
│ ├── 0-0.png
│ └── 1-0.png
└── 2
├── 0-0.png
├── 0-1.png
├── 1-0.png
├── 1-1.png
├── 2-0.png
├── 2-1.png
├── 3-0.png
└── 3-1.png
All tiles in a directory called map, with a second level directory for zoom
level, each file named x-y.png within that.
In my tests on an 32641 x 16471, 8-bit/color RGB PNG, memory usage peaks at around 2.7GB.
On that same test image, the run takes around 63 seconds to create the 11179 tiles, on my fairly underwhelming MacBookPro12,1 (dual core i5).