canvas/bezierCurve.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, user-scalable=0" />
    <title>BezierCurve</title>
    <style>
        *{margin: 0;padding: 0;}
        .canvas{position: fixed;width: 100%;height: 100%;}
    </style>
</head>
<body>
<canvas class="canvas"></canvas>
<script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdn.bootcss.com/touchjs/0.2.14/touch.min.js"></script>
<script>
    var sketch = {

        canvas: null,
        context: null,
        ratio: null,

        isDragging: false,
        draggedPoint: null,
        coordinate: {
            sX: 50,
            sY: 100,
            cX1: 100,
            cY1: 50,
            cX2: 200,
            cY2: 200,
            eX: 300,
            eY: 60
        },
        init: function () {
            var _this = this;

            _this.initCanvas();
            _this.initContext();
            _this.drawBezier();
            _this.drawPoint();
            _this.dragPoint();
        },
        initCanvas: function () {
            var _this = this;
            var canvas = $('.canvas').get(0);
            var context = canvas.getContext('2d');
            var ratio = window.devicePixelRatio || 1;

            canvas.width = canvas.offsetWidth * ratio;
            canvas.height = canvas.offsetHeight * ratio;
            context.scale(ratio, ratio);

            _this.ratio = ratio;
            _this.canvas = canvas;
            _this.context = context;
        },
        initContext: function () {
            var _this = this;

            _this.context.lineWidth = 2;
            _this.context.fillStyle = 'lightgrey';
            _this.context.strokeStyle = 'blueviolet';
        },
        drawBezier: function () {
            var _this = this;
            var coo = _this.coordinate;

            _this.context.beginPath();
            _this.context.moveTo(coo.sX, coo.sY);
            _this.context.bezierCurveTo(coo.cX1, coo.cY1, coo.cX2, coo.cY2, coo.eX, coo.eY);
            _this.context.stroke();
        },
        drawPoint: function (coo) {
            var _this = this;
            var x = 0;
            var y = 0;
            var index = 0;

            $.each(_this.coordinate, function (key, value) {
                if (index % 2) {
                    // 绘制点坐标
                    y = value;
                    // 绘制辅助点
                    _this.context.beginPath();
                    _this.context.arc(x, y, 5, 0, 2 * Math.PI);
                    _this.context.fill();

                    // 触屏点坐标
                    if (coo) {
                        var isInPath = _this.context.isPointInPath(_this.ratio * coo.x, _this.ratio * coo.y);
                        if (isInPath) {
                            _this.isDragging = true;
                            _this.draggedPoint = key;
                        }
                    }
                } else {
                    // 绘制点坐标
                    x = value;
                }

                index += 1;
            });
        },
        dragPoint: function () {
            var _this = this;
            var flag = false;
            var $canvas = $(_this.canvas);
            var width = _this.canvas.width;
            var height = _this.canvas.height;
            var redraw = function (e) {
                if (flag && _this.isDragging) {
                    // 选取点关键字
                    var draggedX = _this.draggedPoint.replace('Y', 'X');
                    var draggedY = _this.draggedPoint;

                    // 重绘贝塞尔曲线及辅助点
                    _this.coordinate[draggedX] = e.pageX;
                    _this.coordinate[draggedY] = e.pageY;
                    _this.context.clearRect(0, 0, width, height);
                    _this.drawBezier();
                    _this.drawPoint();
                }
            };
            var trigger = function (e) {
                var coo = {x: e.pageX, y: e.pageY};

                flag = true;
                _this.drawPoint(coo);
            };

            $canvas.on({
                'mousedown': function (e) {
                    trigger(e);
                },
                'touchstart': function (e) {
                    trigger(e.originalEvent.touches[0]);
                }
            });
            $canvas.on({
                'mouseup': function () {
                    flag = false;
                    _this.isDragging = false;
                },
                'touchend': function () {
                    flag = false;
                    _this.isDragging = false;
                }
            });
            $canvas.on({
                'mousemove': function (e) {
                    redraw(e);
                },
                'touchmove': function (e) {
                    redraw(e.originalEvent.touches[0]);
                }
            });
        }
    };

    sketch.init();
</script>
</body>
</html>