bitmap-sdf

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

Demo

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.

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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