proj-turbo v0.0.1

:warning: this is new and highly experimental and has only been tested on 3 projections so far. I suggest testing it on your data before using it.

proj-turbo

:fire: Turbo-charge your Re-projection Functions

features

• reproject from Web Mercator to EPSG:4326 (Latitude/Longitude) ~3x faster
• reproject from UTM to EPSG:4326 ~5x faster
• zero dependencies
• works great with proj4js
• isomorphic (works in the browser and in NodeJS)

algorithm

This basically checks if reprojection within the given bbox can be modeled by the following function without exceeding the error threshold.

([x, y]) => ([
  x_origin + x_scale * (x - xmin), // x_origin is the smallest possible x output value, xmin is from the given bbox
  y_origin + y_scale * (y - ymin) // y_origin is the smallest possible y output value , ymin is from the given bbox
]);

usage

import proj4 from "proj4";
import { turbocharge } from "proj-turbo";

// convert from EPSG:4326 to EPSG:3857
const reproject = proj4("EPSG:4326", "EPSG:3857");

const reprojectFaster = turbocharge(reproject, {
  // container including points to reproject
  // in the srs that you are reprojecting from
  bbox,

  debug_level = 0,

  // default is false
  // set to true to return undefined instead of throwing an error
  // when proj-turbo can't figure out a faster reprojection function
  quiet = false,

  // the reprojection function we want to try to replace
  // with a faster alternative
  reproject,
  
  // maximum allowable error along the x and y axis
  // in the projection we are reprojecting to.
  // when reprojecting rasters,
  // this will often be the pixel size
  threshold: [x_threshold, y_threshold]
});

thanks

Thanks to Jim Phillips for inspiring me with the awesome performance optimizations he contributed to GeoRasterLayer.