CanvasRenderingContext2D: isPointInStroke() method
The
CanvasRenderingContext2D.isPointInStroke()
method of the Canvas 2D API reports whether or not the specified point is inside the
area contained by the stroking of a path.
Syntax
js
isPointInStroke(x, y)
isPointInStroke(path, x, y)
Parameters
x
-
The x-axis coordinate of the point to check.
y
-
The y-axis coordinate of the point to check.
path
-
A
Path2D
path to check against. If unspecified, the current path is used.
Return value
- A boolean value
-
A Boolean, which is
true
if the point is inside the area contained by the stroking of a path, otherwisefalse
.
Examples
Checking a point in the current path
This example uses the isPointInStroke()
method to check if a point is
within the area of the current path's stroke.
HTML
html
<canvas id="canvas"></canvas>
<p>In stroke: <code id="result">false</code></p>
JavaScript
js
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
const result = document.getElementById("result");
ctx.rect(10, 10, 100, 100);
ctx.stroke();
result.innerText = ctx.isPointInStroke(50, 10);
Result
Checking a point in the specified path
Whenever you move the mouse, this example checks whether the cursor is in the stroke of
an elliptical Path2D
path. If yes, the ellipse's stroke becomes green,
otherwise it is red.
HTML
html
<canvas id="canvas"></canvas>
JavaScript
js
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
// Create ellipse
const ellipse = new Path2D();
ellipse.ellipse(150, 75, 40, 60, Math.PI * 0.25, 0, 2 * Math.PI);
ctx.lineWidth = 25;
ctx.strokeStyle = "red";
ctx.fill(ellipse);
ctx.stroke(ellipse);
// Listen for mouse moves
canvas.addEventListener("mousemove", (event) => {
// Check whether point is inside ellipse's stroke
const isPointInStroke = ctx.isPointInStroke(
ellipse,
event.offsetX,
event.offsetY
);
ctx.strokeStyle = isPointInStroke ? "green" : "red";
// Draw ellipse
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.fill(ellipse);
ctx.stroke(ellipse);
});
Result
Specifications
Specification |
---|
HTML Standard # dom-context-2d-ispointinstroke-dev |
Browser compatibility
BCD tables only load in the browser
See also
- The interface defining this method:
CanvasRenderingContext2D