canvas-demo/canvas.html at main · ygcedu/canvas-demo · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>画板</title>
    <style>
        * {
            margin: 0px;
            padding: 0px;
            box-sizing: border-box
        }

        #canvas {
            display: block;
        }
    </style>
</head>

<body>
<canvas id="canvas" width="100" height="100"></canvas>
<script>
    let canvas = document.getElementById("canvas");
    canvas.width = document.documentElement.clientWidth;
    canvas.height = document.documentElement.clientHeight;
    let ctx = canvas.getContext("2d");
    ctx.fillStyle = "black";
    ctx.strokeStyle = 'black';
    ctx.lineWidth = 8;
    ctx.lineCap = "round";

    let painting = false;
    let last;
    var isTouchDevice = 'ontouchstart' in document.documentElement;
    if (isTouchDevice) {
        // 手机触屏模式下，手指点下
        canvas.ontouchstart = (e) => {
            let x = e.touches[0].clientX;
            let y = e.touches[0].clientY;
            last = [x, y];
        }

        // 手机触屏模式下，手指按住屏幕移动
        canvas.ontouchmove = (e) => {
            let x = e.touches[0].clientX;
            let y = e.touches[0].clientY;
            drawLine(last[0], last[1], x, y);
            last = [x, y];
        }
    } else {
        // PC端鼠标按下
        canvas.onmousedown = (e) => {
            painting = true;
            last = [e.clientX, e.clientY];
        }

        // PC端鼠标按住移动
        canvas.onmousemove = (e) => {
            if (painting === true) {
                drawLine(last[0], last[1], e.clientX, e.clientY);
                last = [e.clientX, e.clientY];
            }
        }

        // PC端鼠标松开
        canvas.onmouseup = () => {
            painting = false;
        }
    }

    // 封装画线方法
    function drawLine(x1, y1, x2, y2){
        ctx.beginPath();
        ctx.moveTo(x1,y1);
        ctx.lineTo(x2,y2);
        ctx.stroke();
    }
</script>
</body>

</html>