canvas绘制折线图(仿echarts)
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2022-05-28 12:34:17
遇到的问题：Retina屏上字体线条模糊问题 解决方案：放大canvas的大小，然后用css压缩回原大小，例如：想要900*400的画布，先将画布设置为 width="1800px" height="800px"，再用css {width: 900px;height: 400px;}压缩。 最终效果 ......
遇到的问题：Retina屏上字体线条模糊问题
解决方案：放大canvas的大小，然后用css压缩回原大小，例如：想要900*400的画布，先将画布设置为 width="1800px" height="800px"，再用css {width: 900px;height: 400px;}压缩。
最终效果如下图：
代码：
1 <!DOCTYPE html>
2 <html lang="en">
3 <head>
4 <meta charset="UTF-8">
5 <title>echarts绘制</title>
6 </head>
7 <body>
8 <canvas id="canvas" width="1800px" height="800px" style="border: 1px solid #ebebed;width: 900px;height: 400px;"></canvas>
9 <script>
10 var scale = 2;
11 var canvas = document.getElementById('canvas');
12 var config = {
13 width: canvas.width,
14 height: canvas.height,
15 Left: 70,
16 Top: 90,
17 Right: 30,
18 Bottom: 60,
19 color: ["#5266d7"],
20 yLine:{
21 splitcount: 8,
22 data:[0,100,200,300,400,500,600,700,800]
23 },
24 xLine:{
25 splitcount: 9,
26 data:[1,2,3,4,5,6,7,8,9,10]
27 },
28 series:{
29 data:[0, 532, 555, 700, 500, 800, 300, 270, 358, 160, 453, 577, 639, 758, 233, 299, 120, 188, 158, 176, 333, 257, 120, 199, 573, 430, 111, 300, 700, 80, 50, 30, 40, 10, 22, 37, 77, 100, 240, 183, 143, 377, 133, 445, 345, 321, 111,12,3,34,456,235,214,43,21]
30 }
31 }
32 var ctx = canvas.getContext('2d');
33 // 绘制title
34 drawText('单位: 次', config.Left, config.Top - 30, 'normal 22px Arial', '#a3a2a7');
35 // 绘制网格线
36 darwBackLine('#cccccc', config.yLine.splitcount, 1, config.yLine.data);
37 // 绘制x轴
38 drawXLine('#939099', config.xLine.splitcount, 2, config.xLine.data);
39 // 绘制线条
40 drawLines(config.color[0], 2,config.series.data);
41 // 绘制图例
42 drawItem('test', config.color[0], 2);
43
44
45 function darwBackLine(color, splitcount, linewidth, data) {
46 var len = Math.floor((config.height - config.Top - config.Bottom)/splitcount);
47 var start = config.Top;
48 for (var i = 0; i < splitcount; i++) {
49 var point = start+len*i;
50 drawLine(config.Left, point, (config.width/2 - config.Right)*scale, point, color, linewidth);
51 drawText(data[splitcount-i], 10, point, 'normal 22px Arial', '#605d68');
52 }
53 drawText(data[splitcount-i], 10, point+len, 'normal 22px Arial', '#605d68');
54 }
55
56 function drawXLine(color, splitcount, linewidth, data) {
57 var left = config.Left;
58 var top = config.height - config.Bottom;
59 var right = (config.width/2 - config.Right)*scale;
60 drawLine(config.Left, top, right, top, color, linewidth);
61 var len = (right - left)/splitcount;
62
63 for (var i = 0; i < splitcount+1; i++) {
64 var xpoint = left+len*i;
65 drawLine(xpoint,top+linewidth,xpoint, top-5*scale, color, linewidth);
66 var PanningLeft = data[i].toString().length*5;
67 drawText(data[i], xpoint-PanningLeft, top+15*scale, 'normal 22px Arial', '#605d68')
68 }
69 }
70
71 function drawLines(color, linewidth, data) {
72 var count = data.length;
73 var left = config.Left;
74 var top = config.height - config.Bottom;
75 var right = (config.width/2 - config.Right)*scale;
76 var len = (right - left)/(count - 1);
77 var i = 0;
78
79 var interval = setInterval(function() {
80 if(i >= count - 1){
81 clearInterval(interval);
82 return;
83 }
84 drawLine(left+len*i, top-(data[i]/800)*(top - config.Top), left+len*(i+1), top-(data[i+1]/800)*(top - config.Top), color, linewidth, 'bevel');
85 i++;
86 }, 30);
87 }
88
89 function drawItem(text, color, linewidth) {
90 var right = (config.width/2 - config.Right)*scale;
91 var left = right-(text.length*10);
92 drawText(text, left, config.Top - 10, 'normal 22px Arial', '#605d68');
93 drawLine(left-20, config.Top - 15, left-80, config.Top - 15, color, linewidth);
94 }
95
96 function drawLine(startX, startY, endX, endY, color, width, lineJoin) {
97 ctx.beginPath();
98 ctx.moveTo(startX, startY);
99 ctx.lineTo(endX, endY);
100 if(color){
101 ctx.strokeStyle = color
102 }
103
104 if(width){
105 ctx.lineWidth = width*scale;
106 }
107
108 if(lineJoin){
109 ctx.lineJoin = lineJoin;
110 }
111
112 ctx.closePath();
113 ctx.stroke();
114 }
115
116 function drawText(text, x, y, font, color) {
117 ctx.font= font;
118 ctx.fillStyle= color;
119 ctx.fillText(text, x, y);
120 }
121 </script>
122 </body>
123 </html>
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