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Example of how to draw hearts on html5 canvas

黄舟
黄舟Original
2017-10-31 10:35:086188browse

The first method

Example of how to draw hearts on html5 canvas
A method of code implementation

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>使用桃心形方程绘制爱心</title>
</head>
<body>
    <canvas></canvas>
    <script>
        var canvas = document.querySelector(&#39;canvas&#39;);
        var ctx = canvas.getContext(&#39;2d&#39;);
        canvas.width = window.innerWidth;
        canvas.height = window.innerHeight;
        var Heart = function(x, y) {
            this.x = x;
            this.y = y;
            this.vertices = [];
            for(let i=0; i<30; i++) {
                var step = i / 30 * (Math.PI * 2);//设置心上面两点之间的角度，具体分成多少份，好像需要去试。
                var vector = {
                    x : (15 * Math.pow(Math.sin(step), 3)),
                    y : -(13 * Math.cos(step) - 5 * Math.cos(2 * step) - 2 * Math.cos(3 * step) - Math.cos(4 * step))
                }
                this.vertices.push(vector);
            }
        }
        Heart.prototype.draw = function() {
            ctx.translate(-1000,this.y);//这一步跟ctx.shadowOffsetX必须一起使用，不明白为啥？
            ctx.beginPath();
            for(let i=0; i<30; i++) {
                var vector = this.vertices[i];
                ctx.lineTo(vector.x, vector.y);
            }
            ctx.shadowColor = "red";
            ctx.shadowOffsetX = this.x+1000;
            ctx.fill();
        }
        canvas.onmousedown = function(e) {
            var x = e.offsetX;
            var y = e.offsetY;
            var heart = new Heart(x, y);
            heart.draw();
        }
    </script>
</body>
</html>

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