594 lines
17 KiB
TypeScript
594 lines
17 KiB
TypeScript
/**
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* The main idea and some parts of the code (e.g. drawing variable width Bézier curve) are taken from:
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* http://corner.squareup.com/2012/07/smoother-signatures.html
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*
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* Implementation of interpolation using cubic Bézier curves is taken from:
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* http://www.benknowscode.com/2012/09/path-interpolation-using-cubic-bezier_9742.html
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*
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* Algorithm for approximated length of a Bézier curve is taken from:
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* http://www.lemoda.net/maths/bezier-length/index.html
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*/
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import { Bezier } from './bezier';
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import { BasicPoint, Point } from './point';
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import { throttle } from './throttle';
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declare global {
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interface CSSStyleDeclaration {
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msTouchAction: string;
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}
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}
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export interface Options {
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dotSize?: number | (() => number);
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minWidth?: number;
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maxWidth?: number;
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minDistance?: number;
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backgroundColor?: string;
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penColor?: string;
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throttle?: number;
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velocityFilterWeight?: number;
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onBegin?: (event: MouseEvent | Touch) => void;
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onEnd?: (event: MouseEvent | Touch) => void;
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}
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export interface PointGroup {
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color: string;
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points: BasicPoint[];
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}
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export default class SignaturePad {
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// Public stuff
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public dotSize: number | (() => number);
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public minWidth: number;
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public maxWidth: number;
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public minDistance: number;
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public backgroundColor: string;
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public penColor: string;
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public throttle: number;
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public velocityFilterWeight: number;
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public onBegin?: (event: MouseEvent | Touch) => void;
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public onEnd?: (event: MouseEvent | Touch) => void;
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// Private stuff
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/* tslint:disable: variable-name */
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private _ctx: CanvasRenderingContext2D;
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private _mouseButtonDown: boolean;
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private _isEmpty: boolean;
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private _lastPoints: Point[]; // Stores up to 4 most recent points; used to generate a new curve
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private _data: PointGroup[]; // Stores all points in groups (one group per line or dot)
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private _lastVelocity: number;
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private _lastWidth: number;
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private _strokeMoveUpdate: (event: MouseEvent | Touch) => void;
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/* tslint:enable: variable-name */
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constructor(
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private canvas: HTMLCanvasElement,
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private options: Options = {},
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) {
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this.velocityFilterWeight = options.velocityFilterWeight || 0.7;
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this.minWidth = options.minWidth || 0.5;
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this.maxWidth = options.maxWidth || 2.5;
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this.throttle = ('throttle' in options ? options.throttle : 16) as number; // in milisecondss
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this.minDistance = ('minDistance' in options
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? options.minDistance
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: 5) as number; // in pixels
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this.dotSize =
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options.dotSize ||
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function dotSize(this: SignaturePad): number {
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return (this.minWidth + this.maxWidth) / 2;
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};
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this.penColor = options.penColor || 'black';
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this.backgroundColor = options.backgroundColor || 'rgba(0,0,0,0)';
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this.onBegin = options.onBegin;
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this.onEnd = options.onEnd;
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this._strokeMoveUpdate = this.throttle
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? throttle(SignaturePad.prototype._strokeUpdate, this.throttle)
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: SignaturePad.prototype._strokeUpdate;
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this._ctx = canvas.getContext('2d') as CanvasRenderingContext2D;
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this.clear();
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// Enable mouse and touch event handlers
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this.on();
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}
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public clear(): void {
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const { _ctx: ctx, canvas } = this;
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// Clear canvas using background color
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ctx.fillStyle = this.backgroundColor;
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ctx.clearRect(0, 0, canvas.width, canvas.height);
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ctx.fillRect(0, 0, canvas.width, canvas.height);
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this._data = [];
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this._reset();
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this._isEmpty = true;
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}
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public fromDataURL(
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dataUrl: string,
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options: { ratio?: number; width?: number; height?: number } = {},
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callback?: (error?: string | Event) => void,
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): void {
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const image = new Image();
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const ratio = options.ratio || window.devicePixelRatio || 1;
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const width = options.width || this.canvas.width / ratio;
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const height = options.height || this.canvas.height / ratio;
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this._reset();
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image.onload = (): void => {
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this._ctx.drawImage(image, 0, 0, width, height);
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if (callback) {
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callback();
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}
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};
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image.onerror = (error): void => {
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if (callback) {
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callback(error);
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}
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};
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image.src = dataUrl;
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this._isEmpty = false;
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}
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public toDataURL(type = 'image/png', encoderOptions?: number): string {
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switch (type) {
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case 'image/svg+xml':
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return this._toSVG();
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default:
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return this.canvas.toDataURL(type, encoderOptions);
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}
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}
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public on(): void {
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// Disable panning/zooming when touching canvas element
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this.canvas.style.touchAction = 'none';
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this.canvas.style.msTouchAction = 'none';
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if (window.PointerEvent) {
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this._handlePointerEvents();
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} else {
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this._handleMouseEvents();
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if ('ontouchstart' in window) {
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this._handleTouchEvents();
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}
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}
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}
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public off(): void {
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// Enable panning/zooming when touching canvas element
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this.canvas.style.touchAction = 'auto';
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this.canvas.style.msTouchAction = 'auto';
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this.canvas.removeEventListener('pointerdown', this._handleMouseDown);
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this.canvas.removeEventListener('pointermove', this._handleMouseMove);
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document.removeEventListener('pointerup', this._handleMouseUp);
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this.canvas.removeEventListener('mousedown', this._handleMouseDown);
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this.canvas.removeEventListener('mousemove', this._handleMouseMove);
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document.removeEventListener('mouseup', this._handleMouseUp);
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this.canvas.removeEventListener('touchstart', this._handleTouchStart);
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this.canvas.removeEventListener('touchmove', this._handleTouchMove);
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this.canvas.removeEventListener('touchend', this._handleTouchEnd);
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}
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public isEmpty(): boolean {
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return this._isEmpty;
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}
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public fromData(pointGroups: PointGroup[]): void {
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this.clear();
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this._fromData(
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pointGroups,
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({ color, curve }) => this._drawCurve({ color, curve }),
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({ color, point }) => this._drawDot({ color, point }),
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);
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this._data = pointGroups;
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}
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public toData(): PointGroup[] {
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return this._data;
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}
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// Event handlers
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private _handleMouseDown = (event: MouseEvent): void => {
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if (event.which === 1) {
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this._mouseButtonDown = true;
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this._strokeBegin(event);
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}
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};
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private _handleMouseMove = (event: MouseEvent): void => {
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if (this._mouseButtonDown) {
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this._strokeMoveUpdate(event);
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}
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};
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private _handleMouseUp = (event: MouseEvent): void => {
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if (event.which === 1 && this._mouseButtonDown) {
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this._mouseButtonDown = false;
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this._strokeEnd(event);
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}
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};
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private _handleTouchStart = (event: TouchEvent): void => {
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// Prevent scrolling.
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event.preventDefault();
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if (event.targetTouches.length === 1) {
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const touch = event.changedTouches[0];
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this._strokeBegin(touch);
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}
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};
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private _handleTouchMove = (event: TouchEvent): void => {
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// Prevent scrolling.
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event.preventDefault();
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const touch = event.targetTouches[0];
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this._strokeMoveUpdate(touch);
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};
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private _handleTouchEnd = (event: TouchEvent): void => {
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const wasCanvasTouched = event.target === this.canvas;
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if (wasCanvasTouched) {
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event.preventDefault();
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const touch = event.changedTouches[0];
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this._strokeEnd(touch);
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}
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};
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// Private methods
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private _strokeBegin(event: MouseEvent | Touch): void {
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const newPointGroup = {
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color: this.penColor,
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points: [],
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};
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if (typeof this.onBegin === 'function') {
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this.onBegin(event);
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}
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this._data.push(newPointGroup);
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this._reset();
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this._strokeUpdate(event);
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}
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private _strokeUpdate(event: MouseEvent | Touch): void {
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if (this._data.length === 0) {
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// This can happen if clear() was called while a signature is still in progress,
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// or if there is a race condition between start/update events.
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this._strokeBegin(event);
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return;
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}
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const x = event.clientX;
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const y = event.clientY;
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const point = this._createPoint(x, y);
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const lastPointGroup = this._data[this._data.length - 1];
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const lastPoints = lastPointGroup.points;
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const lastPoint =
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lastPoints.length > 0 && lastPoints[lastPoints.length - 1];
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const isLastPointTooClose = lastPoint
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? point.distanceTo(lastPoint) <= this.minDistance
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: false;
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const color = lastPointGroup.color;
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// Skip this point if it's too close to the previous one
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if (!lastPoint || !(lastPoint && isLastPointTooClose)) {
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const curve = this._addPoint(point);
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if (!lastPoint) {
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this._drawDot({ color, point });
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} else if (curve) {
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this._drawCurve({ color, curve });
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}
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lastPoints.push({
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time: point.time,
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x: point.x,
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y: point.y,
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});
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}
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}
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private _strokeEnd(event: MouseEvent | Touch): void {
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this._strokeUpdate(event);
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if (typeof this.onEnd === 'function') {
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this.onEnd(event);
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}
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}
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private _handlePointerEvents(): void {
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this._mouseButtonDown = false;
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this.canvas.addEventListener('pointerdown', this._handleMouseDown);
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this.canvas.addEventListener('pointermove', this._handleMouseMove);
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document.addEventListener('pointerup', this._handleMouseUp);
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}
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private _handleMouseEvents(): void {
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this._mouseButtonDown = false;
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this.canvas.addEventListener('mousedown', this._handleMouseDown);
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this.canvas.addEventListener('mousemove', this._handleMouseMove);
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document.addEventListener('mouseup', this._handleMouseUp);
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}
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private _handleTouchEvents(): void {
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this.canvas.addEventListener('touchstart', this._handleTouchStart);
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this.canvas.addEventListener('touchmove', this._handleTouchMove);
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this.canvas.addEventListener('touchend', this._handleTouchEnd);
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}
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// Called when a new line is started
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private _reset(): void {
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this._lastPoints = [];
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this._lastVelocity = 0;
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this._lastWidth = (this.minWidth + this.maxWidth) / 2;
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this._ctx.fillStyle = this.penColor;
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}
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private _createPoint(x: number, y: number): Point {
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const rect = this.canvas.getBoundingClientRect();
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return new Point(x - rect.left, y - rect.top, new Date().getTime());
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}
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// Add point to _lastPoints array and generate a new curve if there are enough points (i.e. 3)
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private _addPoint(point: Point): Bezier | null {
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const { _lastPoints } = this;
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_lastPoints.push(point);
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if (_lastPoints.length > 2) {
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// To reduce the initial lag make it work with 3 points
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// by copying the first point to the beginning.
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if (_lastPoints.length === 3) {
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_lastPoints.unshift(_lastPoints[0]);
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}
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// _points array will always have 4 points here.
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const widths = this._calculateCurveWidths(_lastPoints[1], _lastPoints[2]);
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const curve = Bezier.fromPoints(_lastPoints, widths);
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// Remove the first element from the list, so that there are no more than 4 points at any time.
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_lastPoints.shift();
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return curve;
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}
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return null;
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}
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private _calculateCurveWidths(
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startPoint: Point,
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endPoint: Point,
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): { start: number; end: number } {
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const velocity =
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this.velocityFilterWeight * endPoint.velocityFrom(startPoint) +
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(1 - this.velocityFilterWeight) * this._lastVelocity;
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const newWidth = this._strokeWidth(velocity);
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const widths = {
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end: newWidth,
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start: this._lastWidth,
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};
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this._lastVelocity = velocity;
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this._lastWidth = newWidth;
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return widths;
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}
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private _strokeWidth(velocity: number): number {
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return Math.max(this.maxWidth / (velocity + 1), this.minWidth);
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}
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private _drawCurveSegment(x: number, y: number, width: number): void {
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const ctx = this._ctx;
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ctx.moveTo(x, y);
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ctx.arc(x, y, width, 0, 2 * Math.PI, false);
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this._isEmpty = false;
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}
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private _drawCurve({ color, curve }: { color: string; curve: Bezier }): void {
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const ctx = this._ctx;
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const widthDelta = curve.endWidth - curve.startWidth;
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// '2' is just an arbitrary number here. If only lenght is used, then
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// there are gaps between curve segments :/
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const drawSteps = Math.floor(curve.length()) * 2;
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ctx.beginPath();
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ctx.fillStyle = color;
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for (let i = 0; i < drawSteps; i += 1) {
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// Calculate the Bezier (x, y) coordinate for this step.
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const t = i / drawSteps;
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const tt = t * t;
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const ttt = tt * t;
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const u = 1 - t;
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const uu = u * u;
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const uuu = uu * u;
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let x = uuu * curve.startPoint.x;
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x += 3 * uu * t * curve.control1.x;
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x += 3 * u * tt * curve.control2.x;
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x += ttt * curve.endPoint.x;
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let y = uuu * curve.startPoint.y;
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y += 3 * uu * t * curve.control1.y;
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y += 3 * u * tt * curve.control2.y;
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y += ttt * curve.endPoint.y;
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const width = Math.min(
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curve.startWidth + ttt * widthDelta,
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this.maxWidth,
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);
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this._drawCurveSegment(x, y, width);
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}
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ctx.closePath();
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ctx.fill();
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}
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private _drawDot({
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color,
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point,
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}: {
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color: string;
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point: BasicPoint;
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}): void {
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const ctx = this._ctx;
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const width =
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typeof this.dotSize === 'function' ? this.dotSize() : this.dotSize;
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ctx.beginPath();
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this._drawCurveSegment(point.x, point.y, width);
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ctx.closePath();
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ctx.fillStyle = color;
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ctx.fill();
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}
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private _fromData(
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pointGroups: PointGroup[],
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drawCurve: SignaturePad['_drawCurve'],
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drawDot: SignaturePad['_drawDot'],
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): void {
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for (const group of pointGroups) {
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const { color, points } = group;
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if (points.length > 1) {
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for (let j = 0; j < points.length; j += 1) {
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const basicPoint = points[j];
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const point = new Point(basicPoint.x, basicPoint.y, basicPoint.time);
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// All points in the group have the same color, so it's enough to set
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// penColor just at the beginning.
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this.penColor = color;
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if (j === 0) {
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this._reset();
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}
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const curve = this._addPoint(point);
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if (curve) {
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drawCurve({ color, curve });
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}
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}
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} else {
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this._reset();
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drawDot({
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color,
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point: points[0],
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});
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}
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}
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}
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private _toSVG(): string {
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const pointGroups = this._data;
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const ratio = Math.max(window.devicePixelRatio || 1, 1);
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const minX = 0;
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const minY = 0;
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const maxX = this.canvas.width / ratio;
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const maxY = this.canvas.height / ratio;
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const svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
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svg.setAttribute('width', this.canvas.width.toString());
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svg.setAttribute('height', this.canvas.height.toString());
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this._fromData(
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pointGroups,
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({ color, curve }: { color: string; curve: Bezier }) => {
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const path = document.createElement('path');
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// Need to check curve for NaN values, these pop up when drawing
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// lines on the canvas that are not continuous. E.g. Sharp corners
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// or stopping mid-stroke and than continuing without lifting mouse.
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/* eslint-disable no-restricted-globals */
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if (
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!isNaN(curve.control1.x) &&
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!isNaN(curve.control1.y) &&
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!isNaN(curve.control2.x) &&
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!isNaN(curve.control2.y)
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) {
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const attr =
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`M ${curve.startPoint.x.toFixed(3)},${curve.startPoint.y.toFixed(
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3,
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)} ` +
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`C ${curve.control1.x.toFixed(3)},${curve.control1.y.toFixed(3)} ` +
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`${curve.control2.x.toFixed(3)},${curve.control2.y.toFixed(3)} ` +
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`${curve.endPoint.x.toFixed(3)},${curve.endPoint.y.toFixed(3)}`;
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path.setAttribute('d', attr);
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path.setAttribute('stroke-width', (curve.endWidth * 2.25).toFixed(3));
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path.setAttribute('stroke', color);
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path.setAttribute('fill', 'none');
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path.setAttribute('stroke-linecap', 'round');
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svg.appendChild(path);
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}
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/* eslint-enable no-restricted-globals */
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},
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({ color, point }: { color: string; point: BasicPoint }) => {
|
|
const circle = document.createElement('circle');
|
|
const dotSize =
|
|
typeof this.dotSize === 'function' ? this.dotSize() : this.dotSize;
|
|
circle.setAttribute('r', dotSize.toString());
|
|
circle.setAttribute('cx', point.x.toString());
|
|
circle.setAttribute('cy', point.y.toString());
|
|
circle.setAttribute('fill', color);
|
|
|
|
svg.appendChild(circle);
|
|
},
|
|
);
|
|
|
|
const prefix = 'data:image/svg+xml;base64,';
|
|
const header =
|
|
'<svg' +
|
|
' xmlns="http://www.w3.org/2000/svg"' +
|
|
' xmlns:xlink="http://www.w3.org/1999/xlink"' +
|
|
` viewBox="${minX} ${minY} ${maxX} ${maxY}"` +
|
|
` width="${maxX}"` +
|
|
` height="${maxY}"` +
|
|
'>';
|
|
let body = svg.innerHTML;
|
|
|
|
// IE hack for missing innerHTML property on SVGElement
|
|
if (body === undefined) {
|
|
const dummy = document.createElement('dummy');
|
|
const nodes = svg.childNodes;
|
|
dummy.innerHTML = '';
|
|
|
|
// tslint:disable-next-line: prefer-for-of
|
|
for (let i = 0; i < nodes.length; i += 1) {
|
|
dummy.appendChild(nodes[i].cloneNode(true));
|
|
}
|
|
|
|
body = dummy.innerHTML;
|
|
}
|
|
|
|
const footer = '</svg>';
|
|
const data = header + body + footer;
|
|
|
|
return prefix + btoa(data);
|
|
}
|
|
}
|