嗨,我想在移动滑块时绘制曲线.我有两种曲线.贝塞尔曲线和二次曲线.当我绘制曲线时,我想在同一条路径上移动一个对象.我希望它是动态的,所以如果我能够改变曲线点.
所以我需要一个函数,我可以调用滑块更改,因为我正在为行做.
这是我的代码.此代码仅适用于chrome.
.wrapper {
margin: 0 auto;
width: 1000px;
}
.canHdr {
float: left;
width: 450px;
height: 400px;
border: 1px solid red;
}
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.
[No canvas support]
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.
[No canvas support]
This is my 3rd div with slanting line. I want to move a ball on this line when I move the slider. So as the line increases ball will also move on the line.
[No canvas support]
This is my 4th div with slanting line. I want to move a ball on this line when I move the slider. So as the line increases ball will also move on the line.
[No canvas support]
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();
}
function drawSlopeCurve1(sID, maxValue) {
// erase('canvasTwo');
var canId = 'myCanvas4';
var slideVal = parseInt(document.getElementById(sID).value);
var canvas = document.getElementById(canId);
var context = canvas.getContext('2d');
canvas.width = canvas.width;
//line end points
x1 = 16;
y1 = 170;
x2 = 200;
y2 = 80;
//get slope (rise over run)
var m = (y2 - y1) / (x2 - x1);
//get y-intercept
var b = y1 - (m * x1);
//get distance between the two points
var distance = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
//get new x and y values
var x = x1 + parseInt(distance / maxValue * slideVal);
var y = parseInt(m * x + b);
context.beginPath();
context.moveTo(x1, y1);
context.lineTo(x, y);
context.lineWidth = 0.6;
context.stroke();
newSprite(canId, x, y);
}
function drawSlopeCurve2(sID, maxValue) {
// erase('canvasTwo');
var canId = 'myCanvas3';
var slideVal = parseInt(document.getElementById(sID).value);
var canvas = document.getElementById(canId);
var context = canvas.getContext('2d');
canvas.width = canvas.width;
//line end points
x1 = 16;
y1 = 170;
x2 = 160;
y2 = 72;
//get slope (rise over run)
var m = (y2 - y1) / (x2 - x1);
//get y-intercept
var b = y1 - (m * x1);
//get distance between the two points
var distance = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
//get new x and y values
var x = x1 + parseInt(distance / maxValue * slideVal);
var y = parseInt(m * x + b);
context.beginPath();
context.moveTo(x1, y1);
context.lineTo(x, y);
context.lineWidth = 0.6;
context.stroke();
newSprite(canId, x, y);
}
解决方法:
您应该首先在函数中定义曲线,以便计算每个x位置的图形应该结束的位置.然后你也知道在哪里绘制终点.
我的演示函数有一个在画布上绘制正弦的函数：
function calc(x){
var y = 100 + ( 50*Math.sin(x*400));
return y;
}
通过在点之间绘制一条线(不是曲线！)来获得图形.
for (var x=0; x<=400 && (x <= slider.value); x+=3){
y= calc(x);
ctx.lineTo(x, y);
}
添加了html5slider.js以使滑块在firefox中工作.
标签：javascript,html5-canvas
来源： https://codeday.me/bug/20190709/1409634.html
