How to draw polygons on an HTML5 canvas?
JavascriptCssHtmlCanvasJavascript Problem Overview
I need to know how to draw polygons on a canvas. Without using jQuery or anything like that.
Javascript Solutions
Solution 1 - Javascript
Create a path with moveTo and lineTo (live demo):
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();
Solution 2 - Javascript
from http://www.scienceprimer.com/drawing-regular-polygons-javascript-canvas:
The following code will draw a hexagon. Change the number of sides to create different regular polygons.
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>
Solution 3 - Javascript
//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(let item=2 ; item < poly.length-1 ; item+=2 ){ctx.lineTo( poly[item] , poly[item+1] )}
ctx.closePath();
ctx.fill();
Solution 4 - Javascript
//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');
Solution 5 - Javascript
Here is a function that even supports clockwise/anticlockwise drawing do that you control fills with the non-zero winding rule.
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();
Solution 6 - Javascript
In addition to @canvastag, use a while loop with shift I think is more concise:
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();
Solution 7 - Javascript
You can use the lineTo() method same as: 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();
if you not want to fill the polygon use the stroke() method in the place of fill()
You can also check the following: http://www.authorcode.com/draw-and-fill-a-polygon-and-triangle-in-html5/
thanks
Solution 8 - Javascript
For the people looking for regular polygons:
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);
}
Use:
//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();
Solution 9 - Javascript
To make a simple hexagon without the need for a loop, Just use the beginPath() function. Make sure your canvas.getContext('2d') is the equal to ctx if not it will not work.
I also like to add a variable called times that I can use to scale the object if I need to.This what I don't need to change each number.
// 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();
Solution 10 - Javascript
Let's do that with HTML and get that down to this:
<!DOCTYPE html>
<html>
<head>
<title> SVG hexagon </title>
</head>
<body>
<svg width="300" height="110" >
<polygon point="50 3, 100 28, 100 75, 50 100, 3 75, 3 25" stroke="red" fill="lime" stroke-width="5"/>
</svg>
</body>
</html>
Solution 11 - Javascript
var ctx = document.getElementById('hexagon').getContext('2d');
// hexagon
var numberOfSides = 4,
size = 25,
Xcenter = 40,
Ycenter = 40;
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>