bitmap-sdf

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

Demo

Usage

const calcSdf = require('bitmap-sdf')

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

//calculate distances
const distArr = calcSdf(canvas)

//show distances
const 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] = distArr[j*w+i]*255
		imgArr[j*w*4 + i*4 + 1] = distArr[j*w+i]*255
		imgArr[j*w*4 + i*4 + 2] = distArr[j*w+i]*255
		imgArr[j*w*4 + i*4 + 3] = 255
	}
}
const 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.

See also

• font-atlas-sdf − generate sdf atlas for a font.
• tiny-sdf − fast glyph signed distance field generation.
• optical-properties − glyph optical center and bounding box calculation

Alternatives

• disttransform.wat

License

(c) 2017 Dima Yv. MIT License

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