The CanvasRenderingContext2D.bezierCurveTo()
method of the Canvas 2D API adds a cubic Bézier curve to the current sub-path. It requires three points: the first two are control points and the third one is the end point. The starting point is the latest point in the current path, which can be changed using moveTo()
before creating the Bézier curve.
bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y)
This example shows how a cubic Bézier curve is drawn.
HTML
<canvas id="canvas"></canvas>
JavaScript
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
let start = { x: 50, y: 20 };
let cp1 = { x: 230, y: 30 };
let cp2 = { x: 150, y: 80 };
let end = { x: 250, y: 100 };
ctx.beginPath();
ctx.moveTo(start.x, start.y);
ctx.bezierCurveTo(cp1.x, cp1.y, cp2.x, cp2.y, end.x, end.y);
ctx.stroke();
ctx.fillStyle = "blue";
ctx.beginPath();
ctx.arc(start.x, start.y, 5, 0, 2 * Math.PI);
ctx.arc(end.x, end.y, 5, 0, 2 * Math.PI);
ctx.fill();
ctx.fillStyle = "red";
ctx.beginPath();
ctx.arc(cp1.x, cp1.y, 5, 0, 2 * Math.PI);
ctx.arc(cp2.x, cp2.y, 5, 0, 2 * Math.PI);
ctx.fill();
Result
In this example, the control points are red and the start and end points are blue.
This example draws a simple Bézier curve using bezierCurveTo()
.
HTML
<canvas id="canvas"></canvas>
JavaScript
The curve begins at the point specified by moveTo()
: (30, 30). The first control point is placed at (120, 160), and the second at (180, 10). The curve ends at (220, 140).
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
ctx.beginPath();
ctx.moveTo(30, 30);
ctx.bezierCurveTo(120, 160, 180, 10, 220, 140);
ctx.stroke();
Result