96 lines
2.9 KiB
TypeScript
96 lines
2.9 KiB
TypeScript
import { Point, resizeCanvas, drawCircle, drawLine, cubicBezier } from "./common.js";
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function drawPoints(ctx: CanvasRenderingContext2D, points: Point[]) {
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const [a, b, c, d] = points;
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drawLine(ctx, a, b, 0xFF00FF);
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drawLine(ctx, c, d, 0xFF00FF);
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for (const p of points) {
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drawCircle(ctx, p, 2, 0xFF00FF);
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}
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}
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function drawCurve(ctx: CanvasRenderingContext2D, curve: Point[]) {
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for (let i=0; i < curve.length - 1; ++i) {
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drawLine(ctx, curve[i], curve[i+1], 0xFFFFFF);
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}
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}
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function init() {
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const canvas = document.getElementById("canvas") as HTMLCanvasElement | null;
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if (!canvas) throw new Error("unable to get canvas HTML element");
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const ctx = canvas.getContext("2d") as CanvasRenderingContext2D | null;
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if (!ctx) throw new Error("unable to get canvas 2D context");
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let selection: number | undefined = undefined;
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let points: [Point, Point, Point, Point] = [
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{ x: 227, y: 434 },
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{ x: 341, y: 234 },
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{ x: 649, y: 255 },
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{ x: 765, y: 450 },
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];
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resizeCanvas(ctx); // Init canvas
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drawPoints(ctx, points);
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const bezier = cubicBezier(...points);
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drawCurve(ctx, bezier);
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canvas.ontouchstart = (evt: TouchEvent) => {
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console.assert(evt.touches.length === 1, "Multiple touch points are not supported");
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const { clientX, clientY } = evt.touches[0];
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for (const p of points) {
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if (Math.abs(p.x - clientX) < 10 && Math.abs(p.y - clientY) < 10) {
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selection = points.indexOf(p);
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}
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}
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};
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canvas.onmousedown = (evt: MouseEvent) => {
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const { clientX, clientY } = evt;
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for (const p of points) {
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if (Math.abs(p.x - clientX) < 10 && Math.abs(p.y - clientY) < 10) {
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selection = points.indexOf(p);
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}
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}
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};
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canvas.ontouchmove = (evt: TouchEvent) => {
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console.assert(evt.touches.length === 1, "Multiple touch points are not supported");
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const { clientX, clientY } = evt.touches[0];
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if (selection !== undefined) {
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points[selection].x = clientX;
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points[selection].y = clientY;
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// redraw
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ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
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const bezier = cubicBezier(...points);
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drawCurve(ctx, bezier);
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drawPoints(ctx, points);
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}
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};
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canvas.onmousemove = (evt: MouseEvent) => {
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if (selection !== undefined) {
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points[selection].x = evt.clientX;
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points[selection].y = evt.clientY;
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// redraw
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ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
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const bezier = cubicBezier(...points);
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drawCurve(ctx, bezier);
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drawPoints(ctx, points);
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}
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};
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canvas.ontouchend = () => {
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selection = undefined;
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};
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canvas.onmouseup = () => {
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selection = undefined;
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};
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}
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init();
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