Bitmap-sdf NPM

bitmap-sdf

Calculate signed distance field for an image / bw-data. Fork of tiny-sdf with reduced API.

bitmap-sdf

Usage

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)

dist = calcSdf(source, options?)

Calculate distance field for the input source data, based on options. Returns 1-channel array with distance values from 0..1 range.

Source:

Type	Meaning
Canvas, Context2D	Calculates sdf for the full canvas image data based on `options.channel`, by default `0`, ie. red channel.
ImageData	Calculates sdf for the image data based on `options.channel`
Uint8ClampedArray, Uint8Array	Handles raw pixel data, requires `options.width` and `options.height`. Stride is detected from `width` and `height`.
Float32Array, Array	Handles raw numbers from `0..1` range, requires `options.width` and `options.height`. Stride is detected from `width` and `height`.

Options:

Property	Default	Meaning
`cutoff`	`0.25`	Cutoff parameter, balance between SDF inside `1` and outside `0` of glyph
`radius`	`10`	Max length of SDF, ie. the size of SDF around the `cutoff`
`width`	`canvas.width`	Width of input data, if array
`height`	`canvas.height`	Height of input data, if array
`channel`	`0`	Channel number, `0` is red, `1` is green, `2` is blue, `3` is alpha.
`stride`	`null`	Explicitly indicate number of channels per pixel. Not needed if `height` and `width` are provided.