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test.html
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test.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>canvas大面积数据展示</title>
<style>
#canvas {
background-color: #fff;
border: 1px solid #ccc;
margin: 0 auto;
display: block
}
</style>
</head>
<body>
<canvas height="400" width="600" id="canvas"></canvas>
<script>
var data = [Math.random() * 300];
for (var i = 1; i < 10; i++) { //按照echarts
data.push(Math.round((Math.random() - 0.5) * 20 + data[i - 1]));
}
option = {
canvas:{
id: 'canvas'
},
series: {
name: '模拟数据',
itemStyle: {
color: 'rgb(255, 70, 131)'
},
areaStyle: {
color: 'rgb(255, 158, 68)'
},
data: data
}
}
var ctrlNodesArr = []
var ctrlDrawIndex = 0
function LinearGradient(option) {
this.canvas = document.getElementById(option.canvas.id)
this.ctx = this.canvas.getContext('2d')
this.width = this.canvas.width
this.height = this.canvas.height
this.tooltip = option.tooltip
this.title = option.text
this.xAxis = option.data
this.series = option.series
}
LinearGradient.prototype.initData = function() {
var self = this
var scale = 0.2
var dataMax = 0,
dataMin = this.series.data[0],
diffY = 0,
diffX = 0,
self = this
this.series.data.forEach(function (obj, i) {
if (dataMax < obj) dataMax = obj
if (dataMin > obj) dataMin = obj
})
diffY = this.height / (dataMax - dataMin)
diffX = this.width / this.series.data.length
for(var index = 0; index < this.series.data.length; index ++) {
var last1X = diffX * (index - 1),
last1Y = Math.floor(self.height - diffY * (self.series.data[index - 1] - dataMin)),
last2X = diffX * (index - 2),
last2Y = Math.floor(self.height - diffY * (self.series.data[index - 2] - dataMin)),
nowX = diffX * (index),
nowY = Math.floor(self.height - diffY * (self.series.data[index] - dataMin)),
nextX = diffX * (index + 1),
nextY = Math.floor(self.height - diffY * (self.series.data[index + 1] - dataMin)),
cAx = last1X + (nowX - last2X) * scale,
cAy = last1Y + (nowY - last2Y) * scale,
cBx = nowX - (nextX - last1X) * scale,
cBy = nowY - (nextY - last1Y) * scale
if (index === 1) {
cAx = last1X + (nowX - 0) * scale
cAy = last1Y + (nowY - self.height) * scale
} else if (index === self.series.data.length - 1) {
cBx = nowX - (nowX - last1X) * scale
cBy = nowY - (nowY - last1Y) * scale
}
var obj = {
cAx: cAx,
cAy: cAy,
cBx: cBx,
cBy: cBy,
nowX: nowX,
nowY: nowY,
t: 0
}
ctrlNodesArr.push(obj)
}
}
LinearGradient.prototype.draw = function() {
// dataMax = yMax; dataMin = yMin
var self = this
this.ctx.beginPath()
// this.ctx.lineTo(0, this.height)
ctrlNodesArr.forEach(function(item, index) { //找到前一个点到下一个点中间的控制点
var ctrlAx = item.cAx,
ctrlAy = item.cAy,
ctrlBx = item.cBx,
ctrlBy = item.cBy,
x = item.nowX,
y = item.nowY
self.ctx.bezierCurveTo(ctrlAx, ctrlAy, ctrlBx, ctrlBy, x, y);
})
var lingrad = this.ctx.createLinearGradient(0,0,0,this.width);
lingrad.addColorStop(0, this.series.areaStyle.color);
lingrad.addColorStop(1, this.series.itemStyle.color);
// this.ctx.lineTo(this.width, this.height)
// this.ctx.lineTo(0, this.height)
this.ctx.strokeStyle = this.series.itemStyle.color
this.ctx.stroke()
}
LinearGradient.prototype.drawBall = function() {
var self = this
var item = ctrlNodesArr[ctrlDrawIndex]
var ctrlAx = item.cAx,
ctrlAy = item.cAy,
ctrlBx = item.cBx,
ctrlBy = item.cBy,
x = item.nowX,
y = item.nowY,
ox = 0,
oy = 0
if(ctrlDrawIndex === 0) {
ox = 0
oy = 0
} else {
ox = ctrlNodesArr[ctrlDrawIndex - 1].nowX
oy = ctrlNodesArr[ctrlDrawIndex - 1].nowY
}
if(item.t > 1) {
ctrlDrawIndex++
}else {
self.ctx.clearRect(0, 0, self.width, self.height)
item.t += 0.05
var ballX = ox * Math.pow((1 - item.t), 3) + 3 * ctrlAx * item.t * Math.pow((1 - item.t), 2) + 3 * ctrlBx * Math.pow(item.t, 2) * (1 - item.t) + x * Math.pow(item.t, 3)
var ballY = oy * Math.pow((1 - item.t), 3) + 3 * ctrlAy * item.t * Math.pow((1 - item.t), 2) + 3 * ctrlBy * Math.pow(item.t, 2) * (1 - item.t) + y * Math.pow(item.t, 3)
newMap.draw()
self.ctx.beginPath()
self.ctx.arc(ballX, ballY, 5, 0, Math.PI * 2, false)
self.ctx.fill()
}
if(ctrlDrawIndex !== ctrlNodesArr.length) {
window.requestAnimationFrame(newMap.drawBall.bind(self))
}
}
var newMap = new LinearGradient(option)
newMap.initData()
newMap.drawBall()
</script>
</body>
</html>