@sean.r.hagen/sean-leaflet-geotiff-2

leaflet-geotiff-2

A LeafletJS plugin for displaying geoTIFF raster data. Data can drawn as colored rasters or directon arrows. The layer can be clipped using a polygon.

Version 1 Notice

As of version 1, leaflet-geotiff-2 is now under CSIRO's Open Source Software Licence Agreement, which is a variation of the BSD / MIT License.

There are no other plans for changes to licensing, and the project will remain open source.

---

Instructions

1. Load modules

Dependencies must be loaded:

• Leaflet >= 0.7.7
• geotiff.js == 1.0.0-beta.13
• plotty >= 0.4.4 (optional)

import "leaflet-geotiff-2";

// optional renderers
import "leaflet-geotiff-2/dist/leaflet-geotiff-rgb";
import "leaflet-geotiff-2/dist/leaflet-geotiff-vector-arrows";
import "leaflet-geotiff-2/dist/leaflet-geotiff-plotty"; // requires plotty

2. Add a geoTIFF layer

Parameters:

// GeoTIFF file URL. Currently only EPSG:4326 files are supported
// Can be null if sourceFunction is GeoTIFF.fromArrayBuffer
const url =
  "https://stuartmatthews.github.io/leaflet-geotiff/tif/wind_speed.tif";
const options = {
  // See renderer sections below.
  // One of: L.LeafletGeotiff.rgb, L.LeafletGeotiff.plotty, L.LeafletGeotiff.vectorArrows
  renderer: null,

  // Use a worker thread for some initial compute (recommended for larger datasets)
  useWorker: false,

  // Optional array specifying the corners of the data, e.g. [[40.712216, -74.22655], [40.773941, -74.12544]].
  // If omitted the image bounds will be read from the geoTIFF file (ModelTiepoint).
  bounds: [],

  // Optional geoTIFF band to read
  band: 0,

  // Optional geoTIFF image to read
  image: 0,

  // Optional clipping polygon, provided as an array of [lat,lon] coordinates.
  // Note that this is the Leaflet [lat,lon] convention, not geoJSON [lon,lat].
  clip: undefined,

  // Optional leaflet pane to add the layer.
  pane: "overlayPane",

  // Optional callback to handle failed URL request or parsing of tif
  onError: null,

  // Optional, override default GeoTIFF function used to load source data
  // Oneof: fromUrl, fromBlob, fromArrayBuffer
  sourceFunction: GeoTIFF.fromUrl,

  // Only required if sourceFunction is GeoTIFF.fromArrayBuffer
  arrayBuffer: null,

  // Optional nodata value (integer)
  // (to be ignored by getValueAtLatLng)
  noDataValue: undefined,

  // Optional key to extract nodata value from GeoTIFFImage
  // nested keys can be provided in dot notation, e.g. foo.bar.baz
  // (to be ignored by getValueAtLatLng)
  // this overrides noDataValue, the nodata value should be an integer
  noDataKey: undefined,

  // The block size to use for buffer
  blockSize: 65536,

  // Optional, override default opacity of 1 on the image added to the map
  opacity: 1,

  // Optional, hide imagery while map is moving (may prevent 'flickering' in some browsers)
  clearBeforeMove: false,
};

// create layer
var layer = L.leafletGeotiff(url, options).addTo(map);

Methods - L.leafletGeotiff

method	params	description
getBounds		get leaflet LatLngBounds of the layer
getMinMax		get min max values in data (ignores noDataValue if defined)
getValueAtLatLng	(lat: {Number}, lng: {Number})	get raster value at a point*

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Renderer - Plotty

Useful for single-band raster data.

const options = {
  // Optional. Minimum values to plot.
  displayMin: 0,
  // Optional. Maximum values to plot.
  displayMax: 1,
  // Optional flag for plotty to enable/disable displayMin/Max.
  applyDisplayRange: true,
  // Optional. If true values outside `displayMin` to `displayMax` will be rendered as if they were valid values.
  clampLow: true,
  clampHigh: true,
  // Optional. Plotty color scale used to render the image.
  colorScale: "viridis",
};

const renderer = L.LeafletGeotiff.plotty(options);

Methods - leafletGeotiff.plotty

method	params	description
setColorScale	(colorScale: {String})	set layer color scale
setDisplayRange	(min: {Number}, max: {Number})	set layer display range
setClamps	(clampLow: {Boolean}, clampLow: {Boolean})	set layer clamp options
getColourbarDataUrl	(paletteName: {String})	get a data URI for a color palette (e.g. to display colorbar).
getColorbarOptions		get list of available color palettes

New color scales can be created using plotty's addColorScale method.

---

Renderer - RGB

Useful for multi-band raster data (e.g. true color).

RGB renderer options must currently be added by extending L.leafletGeotiff options.

const renderer = L.LeafletGeotiff.rgb();

const options = {
  // Optional, band index to use as R-band
  rBand: 0,
  // Optional, band index to use as G-band
  gBand: 1,
  // Optional, band index to use as B-band
  bBand: 2,
  // band index to use as alpha-band
  // NOTE: this can also be used in combination with transpValue, then referring to a
  // color band specifying a fixed value to be interpreted as transparent
  alphaBand: 0,
  // for all values equal to transpValue in the band alphaBand, the newly created alpha
  // channel will be set to 0 (transparent), all other pixel values will result in alpha 255 (opaque)
  transpValue: 0,
  renderer: renderer,
};

// create layer
var layer = L.leafletGeotiff(url, options).addTo(map);

---

Renderer - Vector Arrows

For plotting velocity (i.e. quiver plot)

const options = {
  // Optional, size in pixels of direction arrows for vector data.
  arrowSize: 20,
};

const renderer = L.LeafletGeotiff.vectorArrows(options);

---

Advanced usage options

1. Custom renderer can be implemented by extending L.LeafletGeotiffRenderer.

Build

npm install
npm run build

What about the original leaflet-geotiff?

This repo is an attempt to pull together a bunch of community-driven improvements that have been made in various forks of leaflet-geotiff over the years but have failed to make it back into the leaflet-geotiff npm package, and to provide a place for active development for new features.

License

CSIRO Open Source Software Licence Agreement (variation of the BSD / MIT License)