let calcSdf = requrie('bitmap-sdf')

//draw image
let canvas = document.body.appendChild(document.createElement('canvas'))
let w = canvas.width = 200, h = canvas.height = 200
let ctx = canvas.getContext('2d')
ctx.fillStyle = 'white'
ctx.font = 'bold 30px sans-serif'
ctx.fillText('X', 20, 20)

//calculate distances
let distances = calcSdf(canvas)

//show distances
let imgArr = new Uint8ClampedArray(w*h*4)
for (let i = 0; i < w; i++) {
	for (let j = 0; j < h; j++) {
		imgArr[j*w*4 + i*4 + 0] = arr[j*w+i]*255
		imgArr[j*w*4 + i*4 + 1] = arr[j*w+i]*255
		imgArr[j*w*4 + i*4 + 2] = arr[j*w+i]*255
		imgArr[j*w*4 + i*4 + 3] = 255
	}
}
var data = new ImageData(imgArr, w, h)
ctx.putImageData(data, 0, 0)