wip, text-atlas for edt text rendering

src/mol-geo/geometry/text/text-atlas.ts

+/**
+ * Copyright (c) 2019 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ */
+
+import { ParamDefinition as PD } from 'mol-util/param-definition';
+import { edt } from 'mol-math/geometry/distance-transform';
+
+const TextAtlasCache: { [k: string]: TextAtlas } = {}
+
+export function getTextAtlas (props: Partial<TextAtlasProps>) {
+  const hash = JSON.stringify(props)
+  if (TextAtlasCache[ hash ] === undefined) {
+    TextAtlasCache[ hash ] = new TextAtlas(props)
+  }
+  return TextAtlasCache[ hash ]
+}
+
+export type TextFonts = 'sans-serif' | 'monospace' | 'serif' | 'cursive'
+export type TextStyles = 'normal' | 'italic' | 'oblique'
+export type TextVariants = 'normal' | 'small-caps'
+export type TextWeights = 'normal' | 'bold'
+
+export const TextAtlasParams = {
+  fontFamily: PD.Select('sans-serif', [['sans-serif', 'Sans Serif'], ['monospace', 'Monospace'], ['serif', 'Serif'], ['cursive', 'Cursive']] as [TextFonts, string][]),
+  fontSize: PD.Numeric(36, { min: 4, max: 96, step: 1 }),
+  fontStyle: PD.Select('normal', [['normal', 'Normal'], ['italic', 'Italic'], ['oblique', 'Oblique']] as [TextStyles, string][]),
+  fontVariant: PD.Select('normal', [['normal', 'Normal'], ['small-caps', 'Small Caps']] as [TextVariants, string][]),
+  fontWeight: PD.Select('normal', [['normal', 'Normal'], ['bold', 'Bold']] as [TextWeights, string][]),
+
+  width: PD.Numeric(1024),
+  height: PD.Numeric(1024)
+}
+export type TextAtlasParams = typeof TextAtlasParams
+export type TextAtlasProps = PD.Values<TextAtlasParams>
+
+export type TextAtlasMap = { x: number, y: number, w: number, h: number }
+
+export class TextAtlas {
+    readonly props: Readonly<TextAtlasProps>
+    readonly mapped: { [k: string]: TextAtlasMap } = {}
+    readonly placeholder: TextAtlasMap
+    readonly context: CanvasRenderingContext2D
+
+    private canvas: HTMLCanvasElement
+
+    private scratchW = 0
+    private scratchH = 0
+    private currentX = 0
+    private currentY = 0
+
+    private readonly cutoff = 0.25
+    private padding: number
+    private radius: number
+
+    private gridOuter: Float64Array
+    private gridInner: Float64Array
+    private f: Float64Array
+    private d: Float64Array
+    private z: Float64Array
+    private v: Int16Array
+
+    private scratchCanvas: HTMLCanvasElement
+    private scratchContext: CanvasRenderingContext2D
+
+    private lineHeight: number
+    private maxWidth: number
+    private middle: number
+
+    constructor (props: Partial<TextAtlasProps> = {}) {
+        const p = { ...PD.getDefaultValues(TextAtlasParams), ...props }
+        this.props = p
+
+        this.padding = p.fontSize / 8
+        this.radius = p.fontSize / 3
+        this.lineHeight = Math.round(p.fontSize + 6 * this.padding)
+        this.maxWidth = this.lineHeight * 1.5
+
+        // Prepare scratch canvas
+        this.scratchCanvas = document.createElement('canvas')
+        this.scratchCanvas.width = this.maxWidth
+        this.scratchCanvas.height = this.lineHeight
+
+        this.scratchContext = this.scratchCanvas.getContext('2d')!
+        this.scratchContext.font = `${p.fontStyle} ${p.fontVariant} ${p.fontWeight} ${p.fontSize}px ${p.fontFamily}`
+        this.scratchContext.fillStyle = 'black'
+        this.scratchContext.textBaseline = 'middle'
+
+        // temporary arrays for the distance transform
+        this.gridOuter = new Float64Array(this.lineHeight * this.maxWidth)
+        this.gridInner = new Float64Array(this.lineHeight * this.maxWidth)
+        this.f = new Float64Array(Math.max(this.lineHeight, this.maxWidth))
+        this.d = new Float64Array(Math.max(this.lineHeight, this.maxWidth))
+        this.z = new Float64Array(Math.max(this.lineHeight, this.maxWidth) + 1)
+        this.v = new Int16Array(Math.max(this.lineHeight, this.maxWidth))
+
+        this.middle = Math.ceil(this.lineHeight / 2)
+
+        //
+
+        this.canvas = document.createElement('canvas')
+        this.canvas.width = p.width
+        this.canvas.height = p.height
+        this.context = this.canvas.getContext('2d')!
+
+        // Replacement Character
+        this.placeholder = this.map(String.fromCharCode(0xFFFD))
+
+        // Basic Latin (subset)
+        for (let i = 0x0020; i <= 0x007E; ++i) this.map(String.fromCharCode(i))
+
+        // TODO: to slow to always prepare them
+        // // Latin-1 Supplement (subset)
+        // for (let i = 0x00A1; i <= 0x00FF; ++i) this.map(String.fromCharCode(i))
+
+        // Degree sign
+        this.map(String.fromCharCode(0x00B0))
+
+        // // Greek and Coptic (subset)
+        // for (let i = 0x0391; i <= 0x03C9; ++i) this.map(String.fromCharCode(i))
+
+        // // Cyrillic (subset)
+        // for (let i = 0x0400; i <= 0x044F; ++i) this.map(String.fromCharCode(i))
+
+        // Angstrom Sign
+        this.map(String.fromCharCode(0x212B))
+    }
+
+    map (text: string) {
+        if (this.mapped[text] === undefined) {
+            this.draw(text)
+
+            if (this.currentX + this.scratchW > this.props.width) {
+                this.currentX = 0
+                this.currentY += this.scratchH
+            }
+            if (this.currentY + this.scratchH > this.props.height) {
+                console.warn('canvas to small')
+            }
+
+            this.mapped[text] = {
+                x: this.currentX, y: this.currentY,
+                w: this.scratchW, h: this.scratchH
+            }
+
+            this.context.drawImage(
+                this.scratchCanvas,
+                0, 0, this.scratchW, this.scratchH,
+                this.currentX, this.currentY, this.scratchW, this.scratchH
+            )
+
+            this.currentX += this.scratchW
+        }
+
+        return this.mapped[text]
+    }
+
+    get (text: string) {
+        return this.mapped[text] || this.placeholder
+    }
+
+    draw (text: string) {
+        const h = this.lineHeight
+        const ctx = this.scratchContext
+
+        // Measure text
+        const m = ctx.measureText(text)
+        const w = Math.min(this.maxWidth, Math.ceil(m.width + 2 * this.padding + this.radius / 2))
+        const n = w * h
+
+        ctx.clearRect(0, 0, w, h) // clear scratch area
+        ctx.fillText(text, this.padding + this.radius / 4, this.middle) // draw text
+
+        const imageData = ctx.getImageData(0, 0, w, h)
+        const data = imageData.data
+
+        for (let i = 0; i < n; i++) {
+            const a = imageData.data[i * 4 + 3] / 255 // alpha value
+            this.gridOuter[i] = a === 1 ? 0 : a === 0 ? Number.MAX_SAFE_INTEGER : Math.pow(Math.max(0, 0.5 - a), 2)
+            this.gridInner[i] = a === 1 ? Number.MAX_SAFE_INTEGER : a === 0 ? 0 : Math.pow(Math.max(0, a - 0.5), 2)
+        }
+
+        edt(this.gridOuter, w, h, this.f, this.d, this.v, this.z)
+        edt(this.gridInner, w, h, this.f, this.d, this.v, this.z)
+
+        for (let i = 0; i < n; i++) {
+            const d = this.gridOuter[i] - this.gridInner[i];
+            data[i * 4 + 3] = Math.max(0, Math.min(255, Math.round(255 - 255 * (d / this.radius + this.cutoff))));
+        }
+
+        ctx.putImageData(imageData, 0, 0)
+        this.scratchW = w
+        this.scratchH = h
+    }
+}
\ No newline at end of file

src/mol-math/geometry/distance-transform.ts

+/**
+ * Copyright (c) 2019 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ */
+
+/**
+ * 2D Euclidean distance transform by Felzenszwalb & Huttenlocher https://cs.brown.edu/~pff/papers/dt-final.pdf
+ */
+export function edt(data: Helpers.NumberArray, width: number, height: number, f: Helpers.NumberArray, d: Helpers.NumberArray, v: Helpers.NumberArray, z: Helpers.NumberArray) {
+    for (let x = 0; x < width; x++) {
+        for (let y = 0; y < height; y++) {
+            f[y] = data[y * width + x]
+        }
+        edt1d(f, d, v, z, height)
+        for (let y = 0; y < height; y++) {
+            data[y * width + x] = d[y]
+        }
+    }
+    for (let y = 0; y < height; y++) {
+        for (let x = 0; x < width; x++) {
+            f[x] = data[y * width + x]
+        }
+        edt1d(f, d, v, z, width)
+        for (let x = 0; x < width; x++) {
+            data[y * width + x] = Math.sqrt(d[x])
+        }
+    }
+}
+
+/**
+ * 1D squared distance transform
+ */
+function edt1d(f: Helpers.NumberArray, d: Helpers.NumberArray, v: Helpers.NumberArray, z: Helpers.NumberArray, n: number) {
+    v[0] = 0
+    z[0] = Number.MIN_SAFE_INTEGER
+    z[1] = Number.MAX_SAFE_INTEGER
+
+    for (let q = 1, k = 0; q < n; q++) {
+        let s = ((f[q] + q * q) - (f[v[k]] + v[k] * v[k])) / (2 * q - 2 * v[k])
+        while (s <= z[k]) {
+            k--
+            s = ((f[q] + q * q) - (f[v[k]] + v[k] * v[k])) / (2 * q - 2 * v[k])
+        }
+        k++
+        v[k] = q
+        z[k] = s
+        z[k + 1] = Number.MAX_SAFE_INTEGER
+    }
+
+    for (let q = 0, k = 0; q < n; q++) {
+        while (z[k + 1] < q) k++
+        d[q] = (q - v[k]) * (q - v[k]) + f[v[k]]
+    }
+}