Desenhar um gráfico de linhas
Antes de trabalhar, usei o ECharts do Baidu para desenhar um gráfico de linhas. É muito simples começar. Aqui, desenho um gráfico de linhas simples na tela. Aqui, todo o processo de desenho é dividido em várias etapas:
1. Desenho da grade 2. Desenho do sistema de coordenadas 3. Desenho do ponto 4. Desenhe um gráfico de linhas completo combinando as três partes anteriores .
Primeiro, desenhe a grade
代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
canvas {
border: 1px solid #00CED1;
}
</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 X轴的条数 = 画布高度/网格大小*/
var xLineTotal = Math.floor(canvasHeight / gridSize);
for (var i = 0; i <= xLineTotal; i++) {
ctx.beginPath();
ctx.moveTo(0, i * gridSize);
ctx.lineTo(canvasWidth, i * gridSize);
ctx.strokeStyle = '#eee';
ctx.stroke();
}
/*4.画多少条Y轴方向的线 Y轴的条数 = 画布宽度/网格大小*/
var yLineTotal = Math.floor(canvasWidth / gridSize);
for (var i = 0; i <= yLineTotal; i++) {
ctx.beginPath();
ctx.moveTo(i*gridSize ,0);
ctx.lineTo(i*gridSize ,canvasHeight);
ctx.strokeStyle = '#eee';
ctx.stroke();
}
</script>
</body>
</html>
Resultado da operação
Segundo, desenhe o sistema de coordenadas
代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<style>
canvas {
border: 1px solid #00CED1;
}
</style>
</head>
<body>
<canvas width="600" height="400"></canvas>
<script>
var myCanvas = document.querySelector('canvas');
var ctx = myCanvas.getContext('2d');
/*1.绘制坐标系*/
/*2.确定原点*/
/*3.确定距离画布旁边的距离*/
/*4.确定坐标轴的长度*/
/*5.确定箭头的大小 是个等腰三角形 10 */
/*6.绘制箭头填充*/
var space = 20;
var arrowSize = 10;
/*计算原点*/
var canvasWidth = ctx.canvas.width;
var canvasHeight = ctx.canvas.height;
//原点坐标
var x0 = space;
var y0 = canvasHeight - space;
/*绘制x轴*/
ctx.beginPath();
ctx.moveTo(x0, y0);
ctx.lineTo(canvasWidth - space, y0);
/*箭头 三角形 原点 左下 左上 原点*/
ctx.lineTo(canvasWidth - space - arrowSize, y0 + arrowSize / 2);
ctx.lineTo(canvasWidth - space - arrowSize, y0 - arrowSize / 2);
ctx.lineTo(canvasWidth - space, y0);
//填充
ctx.fill();
ctx.stroke();
/*绘制y轴*/
ctx.beginPath();
ctx.moveTo(x0, y0);
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>
Resultado da operação
Terceiro, empate pontos
代码
<html lang="en">
<head>
<meta charset="UTF-8">
<style>
canvas {
border: 1px solid #00CED1;
}
</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;
//相对于正方形 左上 -> 右上 -> 右下 -> 左下
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>
Resultado da operação
Quarto, o gráfico de linhas completo
Mostre o efeito primeiro.
代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
canvas {
border: 1px solid #00CED1;
}
</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);
this.ctx.lineTo(this.canvasWidth, i * this.gridSize);
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);
this.ctx.lineTo(i * this.gridSize, 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>
`` Outros me chamam de gorda, ficarei com raiva, porque admito que sou gorda. Quando outros dizem que sou baixo, acho engraçado porque sei em meu coração que não posso ser baixo. É por isso que estamos zangados com os ataques dos outros. Quem ataca meu escudo é a lança no meu coração (10) `` `