The CanvasRenderingContext2D.quadraticCurveTo()
method of the Canvas 2D API adds a quadratic Bézier curve to the current sub-path. It requires two points: the first one is a control point and the second 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 quadratic Bézier curve.
quadraticCurveTo(cpx, cpy, x, y)
This example shows how a quadratic Bézier curve is drawn.
HTML
<canvas id="canvas"></canvas>
JavaScript
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
ctx.beginPath();
ctx.moveTo(50, 20);
ctx.quadraticCurveTo(230, 30, 50, 100);
ctx.stroke();
ctx.fillStyle = "blue";
ctx.beginPath();
ctx.arc(50, 20, 5, 0, 2 * Math.PI);
ctx.arc(50, 100, 5, 0, 2 * Math.PI);
ctx.fill();
ctx.fillStyle = "red";
ctx.beginPath();
ctx.arc(230, 30, 5, 0, 2 * Math.PI);
ctx.fill();
Result
In this example, the control point is red and the start and end points are blue.
This example draws a simple quadratic Bézier curve using quadraticCurveTo()
.
HTML
<canvas id="canvas"></canvas>
JavaScript
The curve begins at the point specified by moveTo()
: (20, 110). The control point is placed at (230, 150). The curve ends at (250, 20).
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
ctx.beginPath();
ctx.moveTo(20, 110);
ctx.quadraticCurveTo(230, 150, 250, 20);
ctx.stroke();
Result