本文介绍了我想沿特定路径对对象进行动画处理的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着跟版网的小编来一起学习吧！
问题描述
我必须移动路径上的小矩形.在画布内单击后，矩形会移动.
我无法为它设置动画，因为对象只是跳转到所需的点.
请在
<!doctype html><html lang="zh"><头><风格>身体{背景颜色:象牙色；}画布{border:1px 纯红色；}</风格><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><脚本>$(函数(){var canvas=document.getElementById("canvas");var ctx=canvas.getContext("2d");//设置起始值变量 fps = 60;变量百分比=0变种方向=1；//开始动画动画()；函数动画(){//设置动画位置 (0-100)百分比+=方向；如果(百分比<0){百分比=0;方向=1；};如果(百分比> 100){百分比= 100；方向=-1；};平局(百分比)；//请求另一个帧设置超时(函数(){requestAnimationFrame(动画);}, 1000/fps);}//根据sliderValue绘制当前帧函数绘制(滑块值){//重绘路径ctx.clearRect(0,0,canvas.width,canvas.height);ctx.lineWidth = 5;ctx.beginPath();ctx.moveTo(100, 20);ctx.lineTo(200, 160);ctx.strokeStyle = '红色';ctx.stroke();ctx.beginPath();ctx.moveTo(200, 160);ctx.quadraticCurveTo(230, 200, 250, 120);ctx.strokeStyle = '绿色';ctx.stroke();ctx.beginPath();ctx.moveTo(250,120);ctx.bezierCurveTo(290, -40, 300, 200, 400, 150);ctx.strokeStyle = '蓝色';ctx.stroke();ctx.beginPath();ctx.moveTo(400, 150);ctx.lineTo(500, 90);ctx.strokeStyle = '黄金';ctx.stroke();//绘制跟踪矩形变量 xy;如果(滑块值<25){变量百分比=sliderValue/24；xy=getLineXYatPercent({x:100,y:20},{x:200,y:160},百分比);}否则 if(sliderValue<50){var percent=(sliderValue-25)/24xy=getQuadraticBezierXYatPercent({x:200,y:160},{x:230,y:200},{x:250,y:120},百分比);}否则 if(sliderValue<75){var percent=(sliderValue-50)/24xy=getCubicBezierXYatPercent({x:250,y:120},{x:290,y:-40},{x:300,y:200},{x:400,y:150},百分比);}别的 {var percent=(sliderValue-75)/25xy=getLineXYatPercent({x:400,y:150},{x:500,y:90},百分比);}绘制矩形(xy，红色")；}//在 xy 处绘制跟踪矩形函数drawRect(点，颜色){ctx.fillStyle="青色";ctx.strokeStyle="灰色";ctx.lineWidth=3;ctx.beginPath();ctx.rect(point.x-13,point.y-8,25,15);ctx.fill();ctx.stroke();}//在 xy 处绘制跟踪点函数drawDot(点，颜色){ctx.fillStyle=颜色；ctx.strokeStyle="黑色";ctx.lineWidth=3;ctx.beginPath();ctx.arc(point.x,point.y,8,0,Math.PI*2,false);ctx.closePath();ctx.fill();ctx.stroke();}//行:百分比是 0-1函数 getLineXYatPercent(startPt,endPt,percent) {var dx = endPt.x-startPt.x;var dy = endPt.y-startPt.y;var X = startPt.x + dx*percent;var Y = startPt.y + dy*percent;返回({x:X,y:Y})；}//二次贝塞尔曲线:百分比为 0-1函数 getQuadraticBezierXYatPercent(startPt,controlPt,endPt,percent) {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;返回({x:x，y:y})；}//三次贝塞尔百分比为 0-1函数 getCubicBezierXYatPercent(startPt,controlPt1,controlPt2,endPt,percent){var x=CubicN(百分比,startPt.x,controlPt1.x,controlPt2.x,endPt.x);var y=CubicN(百分比,startPt.y,controlPt1.y,controlPt2.y,endPt.y);返回({x:x,y:y});}//距离百分比的三次辅助公式函数 CubicN(pct, a,b,c,d) {var t2 = pct * pct;变量 t3 = t2 * pct;返回 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;}});//结束 $(function(){});</脚本></头><身体><canvas id="canvas" width=600 height=300></canvas></身体></html>I have to move the small rectangle on the path. The rectangle moves after a click inside the canvas.
I am not able to animate it as the object just jumps to the required point.
Please find the code on Fiddle.
HTML
<canvas id="myCanvas" width=578 height=200></canvas>
CSS
#myCanvas {
width:578px;
height:200px;
border:2px thin;
}
JavaScript
var myRectangle = {
x: 100,
y: 20,
width: 25,
height: 10,
borderWidth: 1
};
$(document).ready(function () {
$('#myCanvas').css("border", "2px solid black");
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
var cntxt = canvas.getContext('2d');
drawPath(context);
drawRect(myRectangle, cntxt);
$('#myCanvas').click(function () {
function animate(myRectangle, canvas, cntxt, startTime) {
var time = (new Date()).getTime() - startTime;
var linearSpeed = 10;
var newX = Math.round(Math.sqrt((100 * 100) + (160 * 160)));
if (newX < canvas.width - myRectangle.width - myRectangle.borderWidth / 2) {
myRectangle.x = newX;
}
context.clearRect(0, 0, canvas.width, canvas.height);
drawPath(context);
drawRect(myRectangle, cntxt);
// request new frame
requestAnimFrame(function () {
animate(myRectangle, canvas, cntxt, startTime);
});
}
drawRect(myRectangle, cntxt);
myRectangle.x = 100;
myRectangle.y = 121;
setTimeout(function () {
var startTime = (new Date()).getTime();
animate(myRectangle, canvas, cntxt, startTime);
}, 1000);
});
});
$(document).keypress(function (e) {
if (e.which == 13) {
$('#myCanvas').click();
}
});
function drawRect(myRectangle, cntxt) {
cntxt.beginPath();
cntxt.rect(myRectangle.x, myRectangle.y, myRectangle.width, myRectangle.height);
cntxt.fillStyle = 'cyan';
cntxt.fill();
cntxt.strokeStyle = 'black';
cntxt.stroke();
};
function drawPath(context) {
context.beginPath();
context.moveTo(100, 20);
// line 1
context.lineTo(200, 160);
// quadratic curve
context.quadraticCurveTo(230, 200, 250, 120);
// bezier curve
context.bezierCurveTo(290, -40, 300, 200, 400, 150);
// line 2
context.lineTo(500, 90);
context.lineWidth = 5;
context.strokeStyle = 'blue';
context.stroke();
};
解决方案
Here is how to move an object along a particular path
Animation involves movement over time. So for each "frame" of your animation you need to know the XY coordinate where to draw your moving object (rectangle).
This code takes in a percent-complete (0.00 to 1.00) and returns the XY coordinate which is that percentage along the path segment. For example:
- 0.00 will return the XY at the beginning of the line (or curve).
- 0.50 will return the XY at the middle of the line (or curve).
- 1.00 will return the XY at the end of the line (or curve).
Here is the code to get the XY at the specified percentage along a line:
// line: percent is 0-1
function getLineXYatPercent(startPt,endPt,percent) {
var dx = endPt.x-startPt.x;
var dy = endPt.y-startPt.y;
var X = startPt.x + dx*percent;
var Y = startPt.y + dy*percent;
return( {x:X,y:Y} );
}
Here is the code to get the XY at the specified percentage along a quadratic bezier curve:
// quadratic bezier: percent is 0-1
function getQuadraticBezierXYatPercent(startPt,controlPt,endPt,percent) {
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} );
}
Here is the code to get the XY at the specified percentage along a cubic bezier curve:
// cubic bezier percent is 0-1
function getCubicBezierXYatPercent(startPt,controlPt1,controlPt2,endPt,percent){
var x=CubicN(percent,startPt.x,controlPt1.x,controlPt2.x,endPt.x);
var y=CubicN(percent,startPt.y,controlPt1.y,controlPt2.y,endPt.y);
return({x:x,y:y});
}
// cubic helper 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;
}
And here is how you put it all together to animate the various segments of your path
// calculate the XY where the tracking will be drawn
if(pathPercent<25){
var line1percent=pathPercent/24;
xy=getLineXYatPercent({x:100,y:20},{x:200,y:160},line1percent);
}
else if(pathPercent<50){
var quadPercent=(pathPercent-25)/24
xy=getQuadraticBezierXYatPercent({x:200,y:160},{x:230,y:200},{x:250,y:120},quadPercent);
}
else if(pathPercent<75){
var cubicPercent=(pathPercent-50)/24
xy=getCubicBezierXYatPercent({x:250,y:120},{x:290,y:-40},{x:300,y:200},{x:400,y:150},cubicPercent);
}
else {
var line2percent=(pathPercent-75)/25
xy=getLineXYatPercent({x:400,y:150},{x:500,y:90},line2percent);
}
// draw the tracking rectangle
drawRect(xy);
Here is working code and a Fiddle: http://jsfiddle.net/m1erickson/LumMX/
<!doctype html>
<html lang="en">
<head>
<style>
body{ background-color: ivory; }
canvas{border:1px solid red;}
</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");
// set starting values
var fps = 60;
var percent=0
var direction=1;
// start the animation
animate();
function animate() {
// set the animation position (0-100)
percent+=direction;
if(percent<0){ percent=0; direction=1; };
if(percent>100){ percent=100; direction=-1; };
draw(percent);
// request another frame
setTimeout(function() {
requestAnimationFrame(animate);
}, 1000 / fps);
}
// draw the current frame based on sliderValue
function draw(sliderValue){
// redraw path
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.lineWidth = 5;
ctx.beginPath();
ctx.moveTo(100, 20);
ctx.lineTo(200, 160);
ctx.strokeStyle = 'red';
ctx.stroke();
ctx.beginPath();
ctx.moveTo(200, 160);
ctx.quadraticCurveTo(230, 200, 250, 120);
ctx.strokeStyle = 'green';
ctx.stroke();
ctx.beginPath();
ctx.moveTo(250,120);
ctx.bezierCurveTo(290, -40, 300, 200, 400, 150);
ctx.strokeStyle = 'blue';
ctx.stroke();
ctx.beginPath();
ctx.moveTo(400, 150);
ctx.lineTo(500, 90);
ctx.strokeStyle = 'gold';
ctx.stroke();
// draw the tracking rectangle
var xy;
if(sliderValue<25){
var percent=sliderValue/24;
xy=getLineXYatPercent({x:100,y:20},{x:200,y:160},percent);
}
else if(sliderValue<50){
var percent=(sliderValue-25)/24
xy=getQuadraticBezierXYatPercent({x:200,y:160},{x:230,y:200},{x:250,y:120},percent);
}
else if(sliderValue<75){
var percent=(sliderValue-50)/24
xy=getCubicBezierXYatPercent({x:250,y:120},{x:290,y:-40},{x:300,y:200},{x:400,y:150},percent);
}
else {
var percent=(sliderValue-75)/25
xy=getLineXYatPercent({x:400,y:150},{x:500,y:90},percent);
}
drawRect(xy,"red");
}
// draw tracking rect at xy
function drawRect(point,color){
ctx.fillStyle="cyan";
ctx.strokeStyle="gray";
ctx.lineWidth=3;
ctx.beginPath();
ctx.rect(point.x-13,point.y-8,25,15);
ctx.fill();
ctx.stroke();
}
// draw tracking dot at xy
function drawDot(point,color){
ctx.fillStyle=color;
ctx.strokeStyle="black";
ctx.lineWidth=3;
ctx.beginPath();
ctx.arc(point.x,point.y,8,0,Math.PI*2,false);
ctx.closePath();
ctx.fill();
ctx.stroke();
}
// line: percent is 0-1
function getLineXYatPercent(startPt,endPt,percent) {
var dx = endPt.x-startPt.x;
var dy = endPt.y-startPt.y;
var X = startPt.x + dx*percent;
var Y = startPt.y + dy*percent;
return( {x:X,y:Y} );
}
// quadratic bezier: percent is 0-1
function getQuadraticBezierXYatPercent(startPt,controlPt,endPt,percent) {
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 percent is 0-1
function getCubicBezierXYatPercent(startPt,controlPt1,controlPt2,endPt,percent){
var x=CubicN(percent,startPt.x,controlPt1.x,controlPt2.x,endPt.x);
var y=CubicN(percent,startPt.y,controlPt1.y,controlPt2.y,endPt.y);
return({x:x,y:y});
}
// cubic helper 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>
<canvas id="canvas" width=600 height=300></canvas>
</body>
</html>
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