制作坐标绘图效果 · 前端速查手册

[TOC] >[success] # 制作坐标绘图效果 ~~~ 1.先绘制一个表格 2.在绘制坐标轴 ~~~ >[danger] ##### 绘制一个网格 ![](https://box.kancloud.cn/b4040cff49526f23536794575ccc2815_680x438.png) ~~~ 1.获取画布宽度 ctx.canvas.width 2.获取画布高度 ctx.canvas.height 3.计算可以x轴网格数 var xLineTotal = Math.floor(canvasHeight / gridSize); 4.计算可以y轴网格数 var yLineTotal = Math.floor(canvasWidth / gridSize); 5.绘制x轴平行的网格，x轴期点是0，y轴的起点是设置线条距离，lineTo设置线条的终点也就是画布的宽，y轴的起点是设置线条距离 ~~~ ~~~ <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <style> canvas { border: 1px solid #ccc; } </style> </head> <body> <canvas width="600" height="400"></canvas> <script> var myCanvas = document.querySelector('canvas'); var ctx = myCanvas.getContext('2d'); /*1.绘制网格*/ /*2.网格的大小*/ var gridSize = 10; var canvasHeight = ctx.canvas.height; var canvasWidth = ctx.canvas.width; /*3.画多少条X轴方向的线横线的条数画布高度*/ /*var canvasHeight = myCanvas.height; var canvasWidth = myCanvas.width; console.log(canvasHeight); console.log(canvasWidth);*/ /*console.log(ctx.canvas.width); console.log(ctx.canvas.height);*/ var xLineTotal = Math.floor(canvasHeight / gridSize); for (var i = 0; i <= xLineTotal; i++) { ctx.beginPath(); ctx.moveTo(0, i * gridSize - 0.5 ); ctx.lineTo(canvasWidth, i * gridSize - 0.5); ctx.strokeStyle = '#eee'; ctx.stroke(); } /*4.画多少条Y轴方向的线*/ var yLineTotal = Math.floor(canvasWidth / gridSize); for (var i = 0; i <= yLineTotal; i++) { ctx.beginPath(); ctx.moveTo(i*gridSize - 0.5 ,0); ctx.lineTo(i*gridSize - 0.5 ,canvasHeight); ctx.strokeStyle = '#eee'; ctx.stroke(); } /*5.遍历的形式去画*/ </script> </body> </html> ~~~ >[danger] ##### 绘制X/Y 轴 ![](https://box.kancloud.cn/782efe23af192a048b37f628a3a69f68_602x394.png) ~~~ <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <style> canvas{ border:1px solid #cccccc; } </style> </head> <body> <canvas width="600" height="400"></canvas> <script> var myCanvas = document.querySelector('canvas'); var ctx = myCanvas.getContext('2d'); // space控制坐标轴和画布间的距离 var space=20; // 箭头定位点 var arrowSize = 10; // 计算原点 var canvasWidth = ctx.canvas.width var canvasHeight = ctx.canvas.height var xO = space var yO = canvasHeight - space; // 绘制x轴 ctx.beginPath(); ctx.moveTo(xO,yO) ctx.lineTo(canvasWidth-space,yO) // 绘制箭头 ctx.lineTo(canvasWidth - space - arrowSize, yO + arrowSize / 2); ctx.lineTo(canvasWidth - space - arrowSize, yO - arrowSize / 2); ctx.lineTo(canvasWidth - space, yO); ctx.fill(); ctx.stroke() /*绘制y轴*/ ctx.beginPath(); ctx.moveTo(xO, yO); ctx.lineTo(space, space); /*箭头*/ ctx.lineTo(space + arrowSize / 2, space + arrowSize); ctx.lineTo(space - arrowSize / 2, space + arrowSize); ctx.lineTo(space, space); ctx.fill(); ctx.stroke(); </script> </body> </html> ~~~ >[danger] ##### 画坐标点 ![](https://box.kancloud.cn/05ccf13672db80921404a2d6aa92d956_327x227.png) ~~~ 1.画一个矩形出来填充 ~~~ ~~~ <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <style> canvas { border: 1px solid #ccc; } </style> </head> <body> <canvas width="600" height="400"></canvas> <script> var myCanvas = document.querySelector('canvas'); var ctx = myCanvas.getContext('2d'); /*1.绘制点*/ /*2.点的尺寸*/ /*3.以坐标中心绘制点*/ /*点坐标*/ var coordinate = { x:100, y:100 } /*点尺寸*/ var dottedSize = 10; ctx.moveTo(coordinate.x - dottedSize / 2,coordinate.y - dottedSize / 2); ctx.lineTo(coordinate.x + dottedSize / 2,coordinate.y - dottedSize / 2); ctx.lineTo(coordinate.x + dottedSize / 2,coordinate.y + dottedSize / 2); ctx.lineTo(coordinate.x - dottedSize / 2,coordinate.y + dottedSize / 2); ctx.closePath(); ctx.fill(); </script> </body> </html> ~~~ >[success] # 函数封装折线图 ~~~ <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <style> canvas { border: 1px solid #ccc; } </style> </head> <body> <canvas width="600" height="400"></canvas> <script> /*1.构造函数*/ var LineChart = function (ctx) { /*获取绘图工具*/ this.ctx = ctx || document.querySelector('canvas').getContext('2d'); /*画布的大小*/ this.canvasWidth = this.ctx.canvas.width; this.canvasHeight = this.ctx.canvas.height; /*网格的大小*/ this.gridSize = 10; /*坐标系的间距*/ this.space = 20; /*坐标原点*/ this.x0 = this.space; this.y0 = this.canvasHeight - this.space; /*箭头的大小*/ this.arrowSize = 10; /*绘制点*/ this.dottedSize = 6; /*点的坐标和数据有关系数据可视化*/ } /*2.行为方法*/ LineChart.prototype.init = function (data) { this.drawGrid(); this.drawAxis(); this.drawDotted(data); }; /*绘制网格*/ LineChart.prototype.drawGrid = function () { /*x方向的线*/ var xLineTotal = Math.floor(this.canvasHeight / this.gridSize); this.ctx.strokeStyle = '#eee'; for (var i = 0; i <= xLineTotal; i++) { this.ctx.beginPath(); this.ctx.moveTo(0, i * this.gridSize - 0.5); this.ctx.lineTo(this.canvasWidth, i * this.gridSize - 0.5); this.ctx.stroke(); } /*y方向的线*/ var yLineTotal = Math.floor(this.canvasWidth / this.gridSize); for (var i = 0; i <= yLineTotal; i++) { this.ctx.beginPath(); this.ctx.moveTo(i * this.gridSize - 0.5, 0); this.ctx.lineTo(i * this.gridSize - 0.5, this.canvasHeight); this.ctx.stroke(); } }; /*绘制坐标系*/ LineChart.prototype.drawAxis = function () { /*X轴*/ this.ctx.beginPath(); this.ctx.strokeStyle = '#000'; this.ctx.moveTo(this.x0, this.y0); this.ctx.lineTo(this.canvasWidth - this.space, this.y0); this.ctx.lineTo(this.canvasWidth - this.space - this.arrowSize, this.y0 + this.arrowSize / 2); this.ctx.lineTo(this.canvasWidth - this.space - this.arrowSize, this.y0 - this.arrowSize / 2); this.ctx.lineTo(this.canvasWidth - this.space, this.y0); this.ctx.stroke(); this.ctx.fill(); /*Y轴*/ this.ctx.beginPath(); this.ctx.strokeStyle = '#000'; this.ctx.moveTo(this.x0, this.y0); this.ctx.lineTo(this.space, this.space); this.ctx.lineTo(this.space + this.arrowSize / 2, this.space + this.arrowSize); this.ctx.lineTo(this.space - this.arrowSize / 2, this.space + this.arrowSize); this.ctx.lineTo(this.space, this.space); this.ctx.stroke(); this.ctx.fill(); }; /*绘制所有点*/ LineChart.prototype.drawDotted = function (data) { /*1.数据的坐标需要转换 canvas坐标*/ /*2.再进行点的绘制*/ /*3.把线连起来*/ var that = this; /*记录当前坐标*/ var prevCanvasX = 0; var prevCanvasY = 0; data.forEach(function (item, i) { /* x = 原点的坐标 + 数据的坐标 */ /* y = 原点的坐标 - 数据的坐标 */ var canvasX = that.x0 + item.x; var canvasY = that.y0 - item.y; /*绘制点*/ that.ctx.beginPath(); that.ctx.moveTo(canvasX - that.dottedSize / 2, canvasY - that.dottedSize / 2); that.ctx.lineTo(canvasX + that.dottedSize / 2, canvasY - that.dottedSize / 2); that.ctx.lineTo(canvasX + that.dottedSize / 2, canvasY + that.dottedSize / 2); that.ctx.lineTo(canvasX - that.dottedSize / 2, canvasY + that.dottedSize / 2); that.ctx.closePath(); that.ctx.fill(); /*点的连线*/ /*当时第一个点的时候起点是 x0 y0*/ /*当时不是第一个点的时候起点是上一个点*/ if(i == 0){ that.ctx.beginPath(); that.ctx.moveTo(that.x0,that.y0); that.ctx.lineTo(canvasX,canvasY); that.ctx.stroke(); }else{ /*上一个点*/ that.ctx.beginPath(); that.ctx.moveTo(prevCanvasX,prevCanvasY); that.ctx.lineTo(canvasX,canvasY); that.ctx.stroke(); } /*记录当前的坐标，下一次要用*/ prevCanvasX = canvasX; prevCanvasY = canvasY; }); }; /*3.初始化*/ var data = [ { x: 100, y: 120 }, { x: 200, y: 160 }, { x: 300, y: 240 }, { x: 400, y: 120 }, { x: 500, y: 80 } ]; var lineChart = new LineChart(); lineChart.init(data); </script> </body> </html> ~~~