Node.JS script to generate map tiles from a source image for leaflet.js

generate-map.js

// node .\tools\generate-map.js --bigfile .\src\fullmap.jpg --endpath .\public\grid\ --zoom 7

const fs = require('fs');
const sharp = require('sharp');
const argv = require('yargs').argv;
const _cliProgress = require('cli-progress');

const endPresentFile = argv.bigfile;
const gridPath = argv.endpath;
const bar1 = new _cliProgress.SingleBar({}, _cliProgress.Presets.shades_classic);

let gridDims = 256;
let zoomLevels = argv.zoom;

let generateGridPiece = function(image,x,y){
	return new Promise(resolve => {
		image.extract({left:x*gridDims,top:y*gridDims,width:gridDims,height:gridDims}).toFile(path+y+'.jpg').then(function(){
			resolve(true);
		});
	});
}

async function go(){
	console.log('This will take a while...')
	let bigFile = sharp(endPresentFile).limitInputPixels(false);

	for (var z = zoomLevels; z >= 0; z--) {
		if (!fs.existsSync(gridPath+z)){
		    fs.mkdirSync(gridPath+z);
		}

		let tWidth = gridDims;
		let tHeight = gridDims;
		let pieces = 1;

		if(z > 0){
			pieces = Math.pow(2,z+1)/2;
			percent = z/zoomLevels;
			tWidth = pieces*gridDims;
			tHeight = pieces*gridDims;
		}
		console.log('Starting zoom level '+z+' at '+pieces+'x'+pieces+' ('+tWidth+'x'+tHeight+')');

		let resized = bigFile.clone().resize({width:tWidth,height:tHeight});
		bar1.start(Math.pow(pieces,2),0);

		for (var x = 0; x < pieces; x++) {
			path = gridPath+z+'/'+x+'/';

			if (!fs.existsSync(path)){
			    fs.mkdirSync(path);
			}

			for (var y = 0; y < pieces; y++) {
				var gridpiece = await generateGridPiece(resized,x,y);
				bar1.increment();
			}
		}
		bar1.stop();
	}
}

go();

package.json

{
  "dependencies": {
    "cli-progress": "^3.1.0",
    "sharp": "^0.23.0",
    "yargs": "^14.0.0"
  }
}