Question

我需要知道如何在画布上绘制多边形。不使用jQuery或类似的东西。

Answer 1

使用moveTo和lineTo（live demo）创建路径：

var ctx = canvas.getContext('2d');
ctx.fillStyle = '#f00';
ctx.beginPath();
ctx.moveTo(0, 0);
ctx.lineTo(100,50);
ctx.lineTo(50, 100);
ctx.lineTo(0, 90);
ctx.closePath();
ctx.fill();

Answer 2

//poly [x,y, x,y, x,y.....];
var poly=[ 5,5, 100,50, 50,100, 10,90 ];
var canvas=document.getElementById("canvas")
var ctx = canvas.getContext('2d');
ctx.fillStyle = '#f00';

ctx.beginPath();
ctx.moveTo(poly[0], poly[1]);
for( item=2 ; item < poly.length-1 ; item+=2 ){ctx.lineTo( poly[item] , poly[item+1] )}

ctx.closePath();
ctx.fill();

Answer 3

来自http://www.scienceprimer.com/drawing-regular-polygons-javascript-canvas：

以下代码将绘制六边形。更改边数以创建不同的正多边形。

var ctx = document.getElementById('hexagon').getContext('2d');

// hexagon
var numberOfSides = 6,
    size = 20,
    Xcenter = 25,
    Ycenter = 25;

ctx.beginPath();
ctx.moveTo (Xcenter +  size * Math.cos(0), Ycenter +  size *  Math.sin(0));          

for (var i = 1; i <= numberOfSides;i += 1) {
  ctx.lineTo (Xcenter + size * Math.cos(i * 2 * Math.PI / numberOfSides), Ycenter + size * Math.sin(i * 2 * Math.PI / numberOfSides));
}

ctx.strokeStyle = "#000000";
ctx.lineWidth = 1;
ctx.stroke();

#hexagon { border: thin dashed red; }

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

Answer 4

//create and fill polygon
CanvasRenderingContext2D.prototype.fillPolygon = function (pointsArray, fillColor,     strokeColor) {
    if (pointsArray.length <= 0) return;
    this.moveTo(pointsArray[0][0], pointsArray[0][1]);
    for (var i = 0; i < pointsArray.length; i++) {
        this.lineTo(pointsArray[i][0], pointsArray[i][1]);
    }
    if (strokeColor != null && strokeColor != undefined)
        this.strokeStyle = strokeColor;

    if (fillColor != null && fillColor != undefined) {
        this.fillStyle = fillColor;
        this.fill();
    }
}
//And you can use this method as 
var polygonPoints = [[10,100],[20,75],[50,100],[100,100],[10,100]];
context.fillPolygon(polygonPoints, '#F00','#000');

Answer 5

这是一个甚至支持顺时针/逆时针绘图的功能，您可以使用非零缠绕规则控制填充。

Here is a full article on how it works and more.

// Defines a path for any regular polygon with the specified number of sides and radius, 
// centered on the provide x and y coordinates.
// optional parameters: startAngle and anticlockwise

function polygon(ctx, x, y, radius, sides, startAngle, anticlockwise) {
  if (sides < 3) return;
  var a = (Math.PI * 2)/sides;
  a = anticlockwise?-a:a;
  ctx.save();
  ctx.translate(x,y);
  ctx.rotate(startAngle);
  ctx.moveTo(radius,0);
  for (var i = 1; i < sides; i++) {
    ctx.lineTo(radius*Math.cos(a*i),radius*Math.sin(a*i));
  }
  ctx.closePath();
  ctx.restore();
}

// Example using the function.
// Define a path in the shape of a pentagon and then fill and stroke it.
context.beginPath();
polygon(context,125,125,100,5,-Math.PI/2);
context.fillStyle="rgba(227,11,93,0.75)";
context.fill();
context.stroke();

Answer 6

您可以使用与以下相同的lineTo（）方法： var objctx = canvas.getContext（'2d'）;

        objctx.beginPath();
        objctx.moveTo(75, 50);
        objctx.lineTo(175, 50);
        objctx.lineTo(200, 75);
        objctx.lineTo(175, 100);
        objctx.lineTo(75, 100);
        objctx.lineTo(50, 75);
        objctx.closePath();
        objctx.fillStyle = "rgb(200,0,0)";
        objctx.fill();

如果你不想填充多边形，请在fill（）

的位置使用stroke（）方法

您还可以查看以下内容：http://www.authorcode.com/draw-and-fill-a-polygon-and-triangle-in-html5/

感谢

Answer 7

除了@canvastag之外，请使用while循环shift我认为更简洁：

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

var poly = [5, 5, 100, 50, 50, 100, 10, 90];

// copy array
var shape = poly.slice(0);

ctx.fillStyle = '#f00'
ctx.beginPath();
ctx.moveTo(shape.shift(), shape.shift());
while(shape.length) {
  ctx.lineTo(shape.shift(), shape.shift());
}
ctx.closePath();
ctx.fill();

Answer 8

要制作一个简单的六边形而不需要循环，只需使用beginPath（）函数即可。确保 canvas.getContext（'2d'）等于 ctx ，否则它将无效。

我还想添加一个名为times的变量，如果需要的话，我可以使用它来缩放对象。这不需要我改变每个数字。

     // Times Variable 

     var times = 1;

    // Create a shape

    ctx.beginPath();
    ctx.moveTo(99*times, 0*times);
    ctx.lineTo(99*times, 0*times);
    ctx.lineTo(198*times, 50*times);
    ctx.lineTo(198*times, 148*times);
    ctx.lineTo(99*times, 198*times);
    ctx.lineTo(99*times, 198*times);
    ctx.lineTo(1*times, 148*times);
    ctx.lineTo(1*times,57*times);
    ctx.closePath();
    ctx.clip();
    ctx.stroke();

Answer 9

对于寻找规则多边形的人：

function regPolyPath(r,p,ctx){ //Radius, #points, context
  //Azurethi was here!
  ctx.moveTo(r,0);
  for(i=0; i<p+1; i++){
    ctx.rotate(2*Math.PI/p);
    ctx.lineTo(r,0);
  }
  ctx.rotate(-2*Math.PI/p);
}

使用：

//Get canvas Context
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");

ctx.translate(60,60);    //Moves the origin to what is currently 60,60
//ctx.rotate(Rotation);  //Use this if you want the whole polygon rotated
regPolyPath(40,6,ctx);   //Hexagon with radius 40
//ctx.rotate(-Rotation); //remember to 'un-rotate' (or save and restore)
ctx.stroke();

如何在HTML5画布上绘制多边形？

9 个答案: