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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"
});