 # bitmap-sdf

Calculate SDF for image/bw-data/array

## Stats

StarsIssuesVersionUpdatedCreatedSize
bitmap-sdf
4041.0.4a year ago6 years ago Calculate signed distance field for an image / bw-data. Fork of tiny-sdf with reduced API. Demo

## Usage ```js 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(wh4) 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.