https://github.com/dy/bitmap-sdf
Calculate SDF for image/bitmap/bw data
https://github.com/dy/bitmap-sdf
bitmap sdf
Last synced: 5 months ago
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Calculate SDF for image/bitmap/bw data
- Host: GitHub
- URL: https://github.com/dy/bitmap-sdf
- Owner: dy
- License: mit
- Created: 2017-07-17T22:24:01.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2023-07-19T14:32:15.000Z (over 2 years ago)
- Last Synced: 2025-08-29T21:47:09.317Z (6 months ago)
- Topics: bitmap, sdf
- Language: JavaScript
- Homepage: https://dy.github.io/bitmap-sdf/
- Size: 65.4 KB
- Stars: 53
- Watchers: 2
- Forks: 5
- Open Issues: 4
-
Metadata Files:
- Readme: readme.md
- License: license
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README
# bitmap-sdf [](http://github.com/badges/stability-badges)
Calculate signed distance field for an image / bw-data. Fork of [tiny-sdf](https://github.com/mapbox/tiny-sdf) with reduced API.
[Demo](https://dy.github.io/bitmap-sdf/)
## Usage
[](https://npmjs.org/package/bitmap-sdf/)
```js
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](https://github.com/hughsk/font-atlas-sdf) − generate sdf atlas for a font.
* [tiny-sdf](https://github.com/mapbox/tiny-sdf) − fast glyph signed distance field generation.
* [optical-properties](https://github.com/dfcreative/optical-properties) − glyph optical center and bounding box calculation
## Alternatives
* [disttransform.wat](https://github.com/LingDong-/wasm-fun/blob/master/wat/disttransform.wat)
## License
(c) 2017 Dima Yv. MIT License
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