javascript-html5-canvas在滑块的运动上绘制曲线
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我正在尝试在滑块的运动上绘制二次曲线.因此,随着滑块移动将绘制曲线.我想对二次曲线和贝塞尔曲线都这样做.这是我的代码,仅适用于chrome
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<style type="text/css">
.wrapper {
margin: 0 auto;
width: 1000px;
}
.canHdr {
float: left;
width: 450px;
height: 400px;
border: 1px solid red;
}
</style>
</head>
<body>
<form>
<!-- wrapper -->
<div class="wrapper">
<!-- canHdr -->
<div id="canHdr" class="canHdr" >
<p>
This is my 1st div with quadratic curve I want to draw this curve as I move the slider. I want to make it dynamic so when I should be able to change the curve points. Also I want to move an object on that curve as I am doing in my 3rd div.
</p>
<div class="canOuterHdr" >
<canvas id="myCanvas1" width="300" height="195" style="position: relative;">
[No canvas support]
</canvas>
</div>
<div id="slider1" class="newBg">
<input id="slide1" type="range" min="0" max="100" step="1" value="0" onchange="counterSlider('slide1');" />
</div>
</div>
<!--/ canHdr -->
<!-- canHdr2 -->
<div id="canHdr2" class="canHdr" >
<p>
This is my 2nd div. I have bezier curve. I want to make it dynamic so when I should be able to change the curve points. Also I want to move an object on that curve as I am doing in my 3rd div.
</p>
<div class="canOuterHdr" >
<canvas id="myCanvas2" width="300" height="195" style="position: relative;">
[No canvas support]
</canvas>
</div>
<div id="slider2" class="newBg">
<input id="slide2" type="range" min="0" max="100" step="1" value="0" onchange="counterSlider('slide2');" />
</div>
</div>
<!-- canHdr2 -->
</div>
<!-- /wrapper -->
<script type="text/javascript">
// newSprite('myCanvas3', 16, 170);
quadraticCurve('myCanvas1', 18.8, 45, 28, 160, 228, 165);
bezierCurve('myCanvas2', 20, 75, 55.2, 150.0, 200,100, 228, 165)
function counterSlider(sID) {
var slideVal = document.getElementById(sID).value;
/*if (maxValue ==100){
slideVal=slideVal/100;
}*/
slideVal = slideVal / 100;
if (slideVal == 0) {
/* erase('myCanvas2');
erase('myCanvas3');
erase('myCanvas4');*/
//newSprite('myCanvas1b', 18.8, 45);
// newSprite('myCanvas3', 16, 170);
} else if (slideVal > 0 && slideVal <= 34) {
/*erase('myCanvas1');
//erase('myCanvas1b');
erase('myCanvas2');
erase('myCanvas3');
erase('myCanvas4');*/
} else if (slideVal > 34 && slideVal <= 67) {
/*erase('myCanvas1');
erase('myCanvas2');
erase('myCanvas3');
erase('myCanvas4');*/
} else if (slideVal > 67 && slideVal <= 100) {
/*erase('myCanvas1');
erase('myCanvas2');
erase('myCanvas3');
erase('myCanvas4');*/
}
}
function erase(canvasId) {
var canvas = document.getElementById(canvasId);
var context = canvas.getContext("2d");
context.beginPath();
context.clearRect(0, 0, canvas.width, canvas.height);
canvas.width = canvas.width;
}
/**********for backgroundImage********************/
function quadraticCurve(canId, spx, spy, cpx, cpy, endx, endy) {
var canvas = document.getElementById(canId);
var ctx = canvas.getContext('2d');
ctx.beginPath();
ctx.moveTo(spx, spy);
ctx.quadraticCurveTo(cpx, cpy, endx, endy);
ctx.strokeStyle = "#eaca2d";
ctx.stroke();
}
function bezierCurve(canId, spx, spy, cpx1, cpy1, cpx2, cpy2, endx, endy) {
var canvas = document.getElementById(canId);
var ctx = canvas.getContext('2d');
ctx.beginPath();
ctx.moveTo(spx, spy);
ctx.quadraticCurveTo(cpx1, cpy1, cpx2, cpy2, endx, endy);
ctx.strokeStyle = "#eaca2d";
ctx.stroke();
}
function newSprite(canId, mvx, mvy) {
var canvas = document.getElementById(canId);
var ctx = canvas.getContext('2d');
ctx.globalCompositeOperation = 'source-over';
//ctx.globalCompositeOperation = "destination-over";
ctx.beginPath();
ctx.fillStyle = "#0077c1";
ctx.arc(mvx, mvy, 6, 0, Math.PI * 2, true);
ctx.closePath();
ctx.fill();
}
</script>
</form>
</body>
</html>
这是jsfiddle的链接：http://jsfiddle.net/Y5yYD/1/
解决方法:
以下是逐步绘制四边形&的方法带滑块的三次贝塞尔曲线
小提琴示例：http://jsfiddle.net/m1erickson/auFam/
此函数将返回Quad曲线指定百分比处的XY点：
// quadratic bezier: percent is 0-1
function getQuadraticBezierXY(percent,startPt,controlPt,endPt) {
var x = Math.pow(1-percent,2) * startPt.x + 2 * (1-percent) * percent * controlPt.x + Math.pow(percent,2) * endPt.x;
var y = Math.pow(1-percent,2) * startPt.y + 2 * (1-percent) * percent * controlPt.y + Math.pow(percent,2) * endPt.y;
return( {x:x,y:y} );
}
此函数将以指定的三次曲线百分比返回XY点：
// cubic bezier pct is 0-1
function getCubicBezierXY(pct,startPt,controlPt1,controlPt2,endPt){
var x=CubicN(pct,startPt.x,controlPt1.x,controlPt2.x,endPt.x);
var y=CubicN(pct,startPt.y,controlPt1.y,controlPt2.y,endPt.y);
return({x:x,y:y});
}
// cubic formula at percent distance
function CubicN(pct, a,b,c,d) {
var t2 = pct * pct;
var t3 = t2 * pct;
return a + (-a * 3 + pct * (3 * a - a * pct)) * pct
+ (3 * b + pct * (-6 * b + b * 3 * pct)) * pct
+ (c * 3 - c * 3 * pct) * t2
+ d * t3;
}
这是示例代码和小提琴：http://jsfiddle.net/m1erickson/auFam/
<!doctype html>
<html lang="en">
<head>
<style>
body{ background-color: ivory; }
#wrapper{ position:relative; }
canvas{ position:absolute; left:40px; top:5px; border:1px solid blue;}
#amount{ position:absolute; left:1px; top:5px; margin-bottom:15px; width:23px; border:0; color:#f6931f; font-weight:bold; }
#slider-vertical{ position:absolute; left:5px; top:40px; width:15px; height:225px; border:0px; color:#f6931f; font-weight:bold; }
</style>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.10.3/themes/smoothness/jquery-ui.css" />
<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script src="http://code.jquery.com/ui/1.10.3/jquery-ui.js"></script>
<script>
$(function() {
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
// starting value
var startingSliderValue=50;
drawBoth(startingSliderValue);
$( "#slider-vertical" ).slider({
orientation: "vertical",
range: "min",
min: 0,
max: 100,
value: startingSliderValue,
slide: function( event, ui ) {
$( "#amount" ).val( ui.value );
drawBoth( $("#amount").val() );
}
});
$( "#amount" ).val( $( "#slider-vertical" ).slider( "value" ) );
function drawBoth(sliderValue){
ctx.clearRect(0,0,canvas.width,canvas.height);
drawQuadBezier(sliderValue/100);
drawCubicBezier(sliderValue/100);
}
function drawQuadBezier(pct){
var startPt={ x:18.8, y:45 };
var controlPt={ x:28, y:160};
var endPt={ x:228, y:165 };
ctx.beginPath();
ctx.moveTo(startPt.x,startPt.y);
for(var p=0;p<=pct;p+=.01){
var pt=getQuadraticBezierXY(p,startPt,controlPt,endPt)
ctx.lineTo(pt.x,pt.y);
}
ctx.strokeStyle="green";
ctx.stroke();
var pt=getQuadraticBezierXY(pct,startPt,controlPt,endPt)
drawDot(pt.x,pt.y,"#0077c1");
}
function drawCubicBezier(pct){
var startPt={ x:20, y:75 };
var controlPt1={ x:55.2, y:150};
var controlPt2={ x:200, y:100};
var endPt={ x:228, y:165 };
ctx.beginPath();
ctx.moveTo(startPt.x,startPt.y);
for(var p=0;p<=pct;p+=.01){
var pt=getCubicBezierXY(p,startPt,controlPt1,controlPt2,endPt);
ctx.lineTo(pt.x,pt.y);
}
ctx.strokeStyle="red";
ctx.stroke();
var pt=getCubicBezierXY(pct,startPt,controlPt1,controlPt2,endPt);
drawDot(pt.x,pt.y,"#0077c1");
}
// just draw a dot at xy
function drawDot(x,y,color){
ctx.fillStyle=color;
ctx.beginPath();
ctx.arc(x,y,6,0,Math.PI*2,false);
ctx.closePath();
ctx.fill();
}
// quadratic bezier: percent is 0-1
function getQuadraticBezierXY(percent,startPt,controlPt,endPt) {
var x = Math.pow(1-percent,2) * startPt.x + 2 * (1-percent) * percent * controlPt.x + Math.pow(percent,2) * endPt.x;
var y = Math.pow(1-percent,2) * startPt.y + 2 * (1-percent) * percent * controlPt.y + Math.pow(percent,2) * endPt.y;
return( {x:x,y:y} );
}
// cubic bezier pct is 0-1
function getCubicBezierXY(pct,startPt,controlPt1,controlPt2,endPt){
var x=CubicN(pct,startPt.x,controlPt1.x,controlPt2.x,endPt.x);
var y=CubicN(pct,startPt.y,controlPt1.y,controlPt2.y,endPt.y);
return({x:x,y:y});
}
// cubic formula at percent distance
function CubicN(pct, a,b,c,d) {
var t2 = pct * pct;
var t3 = t2 * pct;
return a + (-a * 3 + pct * (3 * a - a * pct)) * pct
+ (3 * b + pct * (-6 * b + b * 3 * pct)) * pct
+ (c * 3 - c * 3 * pct) * t2
+ d * t3;
}
}); // end $(function(){});
</script>
</head>
<body>
<div id="wrapper">
<input type="text" id="amount" />
<div id="slider-vertical"></div>
<canvas id="canvas" width=300 height=300></canvas>
</div>
</body>
</html>
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