我试图将我的OVERLAY标记显示在我的画布javascript上。我已经完成了所有问题，但没有任何效果！
请帮忙！代码：
page.html中
<!DOCTYPE html>
<html lang="en">
<head>
<link rel="stylesheet" href="style.css">
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<div id='container'>
<canvas id='canvas'></canvas>
<script src="test-script.js"></script>
<div id='overlay'>OVERLAY
<br></br>
OVERLAY
<br></br>
OVERLAY
</div>
</div>
</body>
</html>
style.css
#canvas {position: fixed; z-index: -1;}
#overlay {margin-top: -50px; z-index:0; position: relative;}
测试的script.js
var ns = ns || {};
(function draw() {
var c;
var ctx;
var trails = [];
document.body.onload = function() {
c = document.getElementById( 'canvas' );
c.width = 2000;
c.height = 2000;
document.body.appendChild( c );
ctx = c.getContext( "2d" );
trails.push( new ns.trailer( [990000, 990000, 990000, 600000, 600000 ]));
// trails.push( new ns.trailer( [ 600000,600000,600000,600000,600000,600000,600000 ] ));
trails.push( new ns.trailer( [ 8000000, 8000000, 8000000, 990000, 990000 ] ));
document.onmousedown = reset;
reset();
setInterval( compute, 0 );
}
function reset() {
ctx.fillStyle = "white";
ctx.fillRect( 0,0,c.width,c.height );
for( var i =0; i < trails.length; i++ ) {
trails[ i ].reset();
}
}
function compute() {
for( var i =0; i < trails.length; i++ ) {
trails[ i ].compute( ctx );
}
}
})();
ns.trailer = function( colors ) {
this.points = [];
this.stroke = new ns.stroke( null, 100, 10, colors[ 0 ] );
this.colorIterator = 10;
this.colors = colors;
}
ns.trailer.prototype = {
reset : function() {
this.points = [];
this.width = document.body.offsetWidth;
this.height = document.body.offsetHeight;
this.radius = Math.max( this.width, this.height );
this.center = new ns.point( this.width / 2, this.height / 2 );
this.a0 = Math.random() * Math.PI * 2;
this.a1 = Math.random() * Math.PI * 2;
this.a2 = Math.random() * Math.PI * 2;
var mul = 1 + Math.random() * 2;
if( Math.random() > .5 ) mul *= 5;
else mul /= 2;
this.s0 = ( Math.random() - .5 ) * mul / 180 * Math.PI;
this.s1 = ( Math.random() - .5 ) * mul / 180 * Math.PI;
this.s2 = ( Math.random() - .5 ) * mul / 180 * Math.PI;
},
compute : function( ctx ) {
with( this ) {
a0 += s0;
a1 += s1;
a2 += s2;
var c = Math.cos( a0 ) * Math.cos( a1 ) * Math.cos( a2 );
var s = Math.sin( a0 ) * Math.sin( a1 ) * Math.sin( a2 );
points.push( new ns.point( center.x + c * radius,
center.y + s * radius ) );
if( points.length > 10 ) points.shift();
stroke.anchors = points;
stroke.draw( ctx );
var t = .5 + (Math.sin( new Date().getTime() * .001 ) * .5 );
stroke.color = colors[ Math.floor( t * colors.length ) ];
stroke.width = 25 + ( 1 - t ) * 50;
//stroke.strokeCount = 5 + t * 5;
stroke.strokeCount = 5;
}
}
}
ns.point = function( x,y ) {
this.x = x;
this.y = y;
}
ns.point.prototype = {
add : function( p ) {
return new ns.point( this.x + p.x, this.y + p.y );
}.
sub : function( p ) {
return new ns.point( this.x - p.x, this.y - p.y );
},
negate : function() {
this.x *= -1;
this.y *= -1;
return this;
},
clone : function() {
return new ns.point( this.x, this.y );
},
length : function() {
return Math.sqrt( this.x * this.x + this.y * this.y );
},
normalize : function ( scale ) {
scale = scale || 1;
var l = this.length();
this.x /= l;
this.x *= scale;
this.y /= l;
this.y *= scale;
return this;
}
}
ns.stroke = function( anchors, width, strokeCount, color ) {
this.anchors = anchors;
this.width = width;
this.strokeCount = strokeCount;
this.color = color;
}
ns.stroke.prototype = {
normal : function( p0, p1 ){
return new ns.point( -( p1.y - p0.y ), ( p1.x - p0.x ) );
},
draw : function( ctx ) {
if( this.anchors == undefined ) return;
var half = this.height * .5;
var p, c, n, pnorm, pln, prn, cnorm, cln, crn;
with( this ) {
for( var j = 0; j < strokeCount; j++ ) {
half = width * .5 * Math.random();
var col = ns.variation( color, 35 );
ctx.lineWidth = .1 + Math.random() * 2;
for( var i = 0; i < anchors.length - 2; i++ ) {
p = anchors[ i ];
c = anchors[ i+1 ];
n = anchors[ i+2 ];
pnorm = normal( p, c );
cnorm = normal( c, n );
half += ( Math.random() - .5 );
pnorm.normalize( half );
pln = p.add( pnorm );
pnorm.normalize( -half );
prn = p.add( pnorm );
half += ( Math.random() - .5 );
cnorm.normalize( half );
cln = c.add( cnorm );
cnorm.normalize( -half );
crn = c.add( cnorm );
ctx.beginPath();
ctx.strokeStyle = col;
ctx.moveTo( prn.x, prn.y );
ctx.lineTo( crn.x, crn.y );
ctx.stroke();
ctx.closePath();
ctx.beginPath();
ctx.strokeStyle = col;
ctx.moveTo( pln.x, pln.y );
ctx.lineTo( cln.x, cln.y );
ctx.stroke();
ctx.closePath();
}
}
}
}
}
ns.variation = function( color, amount ) {
amount = amount || 25;
var r = color >> 16 & 0xFF;
var g = color >> 8 & 0xFF;
var b = color & 0xFF;
r += Math.floor( ( Math.random() - .5 ) * amount );
g += Math.floor( ( Math.random() - .5 ) * amount );
b += Math.floor( ( Math.random() - .5 ) * amount );
r = r > 0xFF ? 0xFF : r < 0 ? 0 : r;
g = g > 0xFF ? 0xFF : g < 0 ? 0 : g;
b = b > 0xFF ? 0xFF : b < 0 ? 0 : b;
return "rgba("+r+','+g+','+b+','+Math.random()+');';
}
**我已经添加了我的Javascript代码
答案 0 :(得分：1)
您需要使用absolute位置。还要提到100%的宽度和高度。将元素放在其他元素上应该更高z-index。
#canvas {
position: fixed;
}
#overlay {
z-index: 9;
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
background: rgba(0, 0, 0, 0.3);
}<div id='container'>
<canvas id='canvas'></canvas>
<div id='overlay'>OVERLAY
<br>OVERLAY
<br>OVERLAY
</div>
</div>
答案 1 :(得分：1)
<强> CSS
#container {
position: relative;
}
#overlay {
position:absolute;
top:50px;
left:150px;
z-index:10;
}
调整＆＃34;顶部＆＃34;和＆＃34;左＆＃34;等于将OVERLAY定位在画布顶部。
这是JavaScript。
运行我的代码段。
var ns = ns || {};
(function draw() {
var c;
var ctx;
var trails = [];
document.body.onload = function() {
c = document.getElementById( 'canvas' );
c.width = 2000;
c.height = 2000;
document.body.appendChild( c );
ctx = c.getContext( "2d" );
trails.push( new ns.trailer( [990000, 990000, 990000, 600000, 600000 ]));
// trails.push( new ns.trailer( [ 600000,600000,600000,600000,600000,600000,600000 ] ));
trails.push( new ns.trailer( [ 8000000, 8000000, 8000000, 990000, 990000 ] ));
document.onmousedown = reset;
reset();
setInterval( compute, 0 );
};
function reset() {
ctx.fillStyle = "white";
ctx.fillRect( 0,0,c.width,c.height );
for( var i =0; i < trails.length; i++ ) {
trails[ i ].reset();
}
}
function compute() {
for( var i =0; i < trails.length; i++ ) {
trails[ i ].compute( ctx );
}
}
})();
ns.trailer = function( colors ) {
this.points = [];
this.stroke = new ns.stroke( null, 100, 10, colors[ 0 ] );
this.colorIterator = 10;
this.colors = colors;
};
ns.trailer.prototype = {
reset : function() {
this.points = [];
this.width = document.body.offsetWidth;
this.height = document.body.offsetHeight;
this.radius = Math.max( this.width, this.height );
this.center = new ns.point( this.width / 2, this.height / 2 );
this.a0 = Math.random() * Math.PI * 2;
this.a1 = Math.random() * Math.PI * 2;
this.a2 = Math.random() * Math.PI * 2;
var mul = 1 + Math.random() * 2;
if( Math.random() > .5 ) mul *= 5;
else mul /= 2;
this.s0 = ( Math.random() - .5 ) * mul / 180 * Math.PI;
this.s1 = ( Math.random() - .5 ) * mul / 180 * Math.PI;
this.s2 = ( Math.random() - .5 ) * mul / 180 * Math.PI;
},
compute : function( ctx ) {
with( this ) {
a0 += s0;
a1 += s1;
a2 += s2;
var c = Math.cos( a0 ) * Math.cos( a1 ) * Math.cos( a2 );
var s = Math.sin( a0 ) * Math.sin( a1 ) * Math.sin( a2 );
points.push( new ns.point( center.x + c * radius,
center.y + s * radius ) );
if( points.length > 10 ) points.shift();
stroke.anchors = points;
stroke.draw( ctx );
var t = .5 + (Math.sin( new Date().getTime() * .001 ) * .5 );
stroke.color = colors[ Math.floor( t * colors.length ) ];
stroke.width = 25 + ( 1 - t ) * 50;
//stroke.strokeCount = 5 + t * 5;
stroke.strokeCount = 5;
}
}
};
ns.point = function( x,y ) {
this.x = x;
this.y = y;
};
ns.point.prototype = {
add : function( p ) {
return new ns.point( this.x + p.x, this.y + p.y );
},
sub : function( p ) {
return new ns.point( this.x - p.x, this.y - p.y );
},
negate : function() {
this.x *= -1;
this.y *= -1;
return this;
},
clone : function() {
return new ns.point( this.x, this.y );
},
length : function() {
return Math.sqrt( this.x * this.x + this.y * this.y );
},
normalize : function ( scale ) {
scale = scale || 1;
var l = this.length();
this.x /= l;
this.x *= scale;
this.y /= l;
this.y *= scale;
return this;
}
};
ns.stroke = function( anchors, width, strokeCount, color ) {
this.anchors = anchors;
this.width = width;
this.strokeCount = strokeCount;
this.color = color;
};
ns.stroke.prototype = {
normal : function( p0, p1 ){
return new ns.point( -( p1.y - p0.y ), ( p1.x - p0.x ) );
},
draw : function( ctx ) {
if( this.anchors === undefined ) return;
var half = this.height * .5;
var p, c, n, pnorm, pln, prn, cnorm, cln, crn;
with( this ) {
for( var j = 0; j < strokeCount; j++ ) {
half = width * .5 * Math.random();
var col = ns.variation( color, 35 );
ctx.lineWidth = .1 + Math.random() * 2;
for( var i = 0; i < anchors.length - 2; i++ ) {
p = anchors[ i ];
c = anchors[ i+1 ];
n = anchors[ i+2 ];
pnorm = normal( p, c );
cnorm = normal( c, n );
half += ( Math.random() - .5 );
pnorm.normalize( half );
pln = p.add( pnorm );
pnorm.normalize( -half );
prn = p.add( pnorm );
half += ( Math.random() - .5 );
cnorm.normalize( half );
cln = c.add( cnorm );
cnorm.normalize( -half );
crn = c.add( cnorm );
ctx.beginPath();
ctx.strokeStyle = col;
ctx.moveTo( prn.x, prn.y );
ctx.lineTo( crn.x, crn.y );
ctx.stroke();
ctx.closePath();
ctx.beginPath();
ctx.strokeStyle = col;
ctx.moveTo( pln.x, pln.y );
ctx.lineTo( cln.x, cln.y );
ctx.stroke();
ctx.closePath();
}
}
}
}
};
ns.variation = function( color, amount ) {
amount = amount || 25;
var r = color && 16 && 0xFF;
var g = color && 8 && 0xFF;
var b = color && 0xFF;
r += Math.floor( ( Math.random() - .5 ) * amount );
g += Math.floor( ( Math.random() - .5 ) * amount );
b += Math.floor( ( Math.random() - .5 ) * amount );
r = r > 0xFF ? 0xFF : r < 0 ? 0 : r;
g = g > 0xFF ? 0xFF : g < 0 ? 0 : g;
b = b > 0xFF ? 0xFF : b < 0 ? 0 : b;
return "rgba("+r+','+g+','+b+','+Math.random()+');';
};#container {
position: relative;
}
#overlay {
position:absolute;
top:50px;
left:150px;
z-index:10;
}<body>
<div id='container'>
<div id='overlay'>
<h1>
OVERLAY
</h1>
</div>
<canvas id='canvas'>
</canvas>
</div>
<!-- scripts -->
<script type="text/javascript" src="test-script.js"></script>
</body>