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Advanced Features

Custom Draw Function

You can directly edit the canvas that is being rendered by passing in a customDrawFunction. The custom draw function takes in an object with the following keys:

  • values: an array of pixel values with each element representing one band
  • context: the browser's context object
  • x: how far from the left side of the canvas does drawing start
  • y: how far from the top of the canvas does drawing start
  • width: how wide in screen pixels is the rectangular representation of a raster pixel sampled from the original raster
  • height: how tall in screen pixels is the rectangular representation of a raster pixel sampled from the original raster
  • rasterX: how far from the left edge of the original raster in original raster pixels
  • rasterY: how far from the top edge of the original raster in original raster pixels
  • sampleX: how many samples in from the left of the available pixels. When reading from a Cloud Optimized GeoTIFF, this is equivalent to number of pixels in from the left edge of the fetched pixels.
  • sampleY: how many samples in from the top of the available pixels. When reading from a Cloud Optimized GeoTIFF, this is equivalent to number of pixels in from the top edge of the fetched pixels.
  • sampledRaster: only applicable when reading from a Cloud Optimized GeoTIFF. This refers to the pixels fetched from the remote GeoTIFF.

Here's a rough example implementing drawing of wind direction arrows: https://geotiff.github.io/georaster-layer-for-leaflet-example/examples/wind-direction-arrows.html and the source code for it.

Setting the Log Level

You can turn on extra console logging for debugging purposes by setting the debugLevel to 1 or greater.

new GeoRasterLayer({
  georaster,
  debugLevel: 1
})

Reducing your Build Size

The default builds of GeoRasterLayer include support for nearly all projections. Of course, this increases the total build size of the library by a lot, specifically from about 54kb to 311kb. If you don't want this built-in support, you can use the lite version of the library, which is found at ./dist/georaster-layer-for-leaflet.lite.min.js. This means you'll want to do const GeoRasterLayer = require('georaster-layer-for-leaflet/dist/georaster-layer-for-leaflet.lite.min.js') or import GeoRasterLayer from 'georaster-layer-for-leaflet/dist/georaster-layer-for-leaflet.lite.min.js when loading the library.

Masking

You can hide all the pixels either inside or outside a given mask geometry. You can provide a JSON object as a mask geometry or a URL to a GeoJSON.

// only display what is inside the borders of the USA
new GeoRasterLayer({
  georaster,
  mask: "./usa.geojson",
  mask_strategy: "inside"
});

// hide all the land masses
new GeoRasterLayer({
  georaster,
  mask: { type: "FeatureCollection", features: [ /* .. */] }, // a GeoJSON for the world's oceans
  mask_strategy: "outside"
});

Turbo Mode

You can enable turbo mode, which will in some cases lead to better performance. However, it is experimental, so should be tested first on your data before using in production. Internally, it uses proj-turbo.