HTML5 canvas basic drawing: drawing five-pointed star

5ba626b379994d53f7acf72a64f9b697c2caaf3fc160dd2513ce82f021917f8b is a new tag in HTML5, used to draw graphics. In fact, this tag is the same as other tags. The special thing is that this tag can Get a CanvasRenderingContext2D object, we can control the object for drawing through JavaScript script.
5ba626b379994d53f7acf72a64f9b697c2caaf3fc160dd2513ce82f021917f8b is just a container for drawing graphics. In addition to attributes such as id, class, style, etc., it also has height and width attributes. There are three main steps for drawing on the 5ba626b379994d53f7acf72a64f9b697> element:
1. Get the DOM object corresponding to the 5ba626b379994d53f7acf72a64f9b697 element, which is a Canvas object;
2. Call the getContext() method of the Canvas object, Get a CanvasRenderingContext2D object;
3. Call the CanvasRenderingContext2D object for drawing.

By analyzing the five-pointed star, we can determine the rules of the coordinates of each vertex. One thing to note here is: in the canvas, the direction of the Y-axis is downward.



The corresponding code is as follows:

var canvas = document.getElementById("canvas");   

        var context = canvas.getContext("2d");   

        context.beginPath();   

        //设置是个顶点的坐标，根据顶点制定路径   

        for (var i = 0; i < 5; i++) {   

            context.lineTo(Math.cos((18+i*72)/180*Math.PI)*200+200,   

                            -Math.sin((18+i*72)/180*Math.PI)*200+200);   

            context.lineTo(Math.cos((54+i*72)/180*Math.PI)*80+200,   

                            -Math.sin((54+i*72)/180*Math.PI)*80+200);   

        }   

        context.closePath();   

        //设置边框样式以及填充颜色   

        context.lineWidth="3";   

        context.fillStyle = "#F6F152";   

        context.strokeStyle = "#F5270B";   

        context.fill();   

        context.stroke();

Final effect: