CanvasRenderingContext2D.stroke() - Web APIs 编辑

The CanvasRenderingContext2D.stroke() method of the Canvas 2D API strokes (outlines) the current or given path with the current stroke style.

Strokes are aligned to the center of a path; in other words, half of the stroke is drawn on the inner side, and half on the outer side.

The stroke is drawn using the non-zero winding rule, which means that path intersections will still get filled.

Syntax

void ctx.stroke();
void ctx.stroke(path);

Parameters

path

A Path2D path to stroke.

Examples

A simple stroked rectangle

This example creates a rectangle using the rect() method, and then draws it to the canvas using stroke().

HTML

<canvas id="canvas"></canvas>

JavaScript

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
ctx.rect(10, 10, 150, 100);
ctx.stroke();

Result

Re-stroking paths

Typically, you'll want to call beginPath() for each new thing you want to stroke. If you don't, the previous sub-paths will remain part of the current path, and get stroked every time you call the stroke() method. In some cases, however, this may be the desired effect.

HTML

<canvas id="canvas"></canvas>

JavaScript

This code strokes the first path three times, the second path two times, and the third path only once.

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');

// First sub-path
ctx.lineWidth = 26;
ctx.strokeStyle = 'orange';
ctx.moveTo(20, 20);
ctx.lineTo(160, 20);
ctx.stroke();

// Second sub-path
ctx.lineWidth = 14;
ctx.strokeStyle = 'green';
ctx.moveTo(20, 80);
ctx.lineTo(220, 80);
ctx.stroke();

// Third sub-path
ctx.lineWidth = 4;
ctx.strokeStyle = 'pink';
ctx.moveTo(20, 140);
ctx.lineTo(280, 140);
ctx.stroke();

Result

Stroking and filling

If you want to both stroke and fill a path, the order in which you perform these actions will determine the result. In this example, the square on the left is drawn with the stroke on top of the fill. The square on the right is drawn with the fill on top of the stroke.

HTML

<canvas id="canvas"></canvas>

JavaScript

const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');

ctx.lineWidth = 16;
ctx.strokeStyle = 'red';

// Stroke on top of fill
ctx.beginPath();
ctx.rect(25, 25, 100, 100);
ctx.fill();
ctx.stroke();

// Fill on top of stroke
ctx.beginPath();
ctx.rect(175, 25, 100, 100);
ctx.stroke();
ctx.fill();

Result

Specifications

Browser compatibility

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See also

• The interface defining this method: CanvasRenderingContext2D