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