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用canvas绘制折线图
1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4 <meta charset="UTF-8"> 5 <title>用canvas绘制折线图</title> 6 </head> 7 <body> 8 <canvas id="cv"></canvas> 9 </body>10 </html>11 <script>12 var cv = document.getElementById("cv");13 cv.width = 600;14 cv.height = 400;15 cv.style.border = "1px solid red";16 var ctx = cv.getContext("2d");17 var data2 = [.3, .1, .2, .4, .2, .7, .3, .9];18 var data3 = [3, 12, 14, 17, 29, 33, 40, 52];19 20 getBrokenLine(data2, "#f00");21 getBrokenLine(data3, "#0f0");22 23 //封装一个折线图的函数24 function getBrokenLine(data, color) {25 var maxNum = Math.max.apply(null, data); //求数组中的最大值26 var padding = 20, //边距27 x0 = padding, //原点x轴坐标28 y0 = cv.height - padding, //原点y轴坐标29 xArrow_x = padding, //x轴箭头处坐标x30 xArrow_y = padding, //x轴箭头处坐标y31 yArrow_x = cv.width - padding, //y轴箭头处坐标x32 yArrow_y = cv.height - padding, //y轴箭头处坐标y33 arrowWidth = 10, //箭头的宽度34 xLength = cv.width - 2*padding - arrowWidth, //x轴的长度35 yLength = cv.height - 2*padding - arrowWidth, //y轴的长度36 pointsWidth = xLength/(data.length + 1); //折线上每个点之间的距离37 38 ctx.beginPath();//控制绘制的折线不受坐标轴样式属性的影响39 //绘制x轴40 ctx.moveTo(x0, y0);41 ctx.lineTo(xArrow_x, xArrow_y);42 ctx.moveTo(xArrow_x, xArrow_y);43 ctx.lineTo(xArrow_x - arrowWidth, xArrow_y + arrowWidth);44 ctx.moveTo(xArrow_x, xArrow_y);45 ctx.lineTo(xArrow_x + arrowWidth, xArrow_y + arrowWidth);46 47 //绘制y轴48 ctx.moveTo(x0, y0);49 ctx.lineTo(yArrow_x, yArrow_y);50 ctx.moveTo(yArrow_x, yArrow_y);51 ctx.lineTo(yArrow_x - arrowWidth, yArrow_y - arrowWidth);52 ctx.moveTo(yArrow_x, yArrow_y);53 ctx.lineTo(yArrow_x - arrowWidth, yArrow_y + arrowWidth);54 ctx.strokeStyle = "#000";55 56 //中断（坐标轴和折线的）连接57 ctx.stroke();58 ctx.beginPath();59 60 //绘制折线61 for (var i = 0; i < data.length; i++) {62 var pointX = padding + (i + 1) * pointsWidth;63 var pointY = padding + arrowWidth + (1 - data[i]/maxNum) * yLength;64 ctx.lineTo(pointX, pointY);65 }66 ctx.strokeStyle = color;67 ctx.stroke();68 }69 </script>
效果图如下：
用canvas绘制折线图
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