我正在尝试在网站上使用圣诞节 Javascript 叠加层，我使用的标签显示在我网站的其余内容上。
window.onload = function(){
//canvas init
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
//canvas dimensions
var W = window.innerWidth;
var H = window.innerHeight;
canvas.width = W;
canvas.height = H;
//snowflake particles
var mp = 25; //max particles
var particles = [];
for(var i = 0; i < mp; i++)
{
particles.push({
x: Math.random()*W, //x-coordinate
y: Math.random()*H, //y-coordinate
r: Math.random()*4+1, //radius
d: Math.random()*mp //density
})
}
//Lets draw the flakes
function draw()
{
ctx.clearRect(0, 0, W, H);
ctx.fillStyle = "rgba(255, 255, 255, 0.8)";
ctx.beginPath();
for(var i = 0; i < mp; i++)
{
var p = particles[i];
ctx.moveTo(p.x, p.y);
ctx.arc(p.x, p.y, p.r, 0, Math.PI*2, true);
}
ctx.fill();
update();
}
//Function to move the snowflakes
//angle will be an ongoing incremental flag. Sin and Cos functions will be applied to it to create vertical and horizontal movements of the flakes
var angle = 0;
function update()
{
angle += 0.01;
for(var i = 0; i < mp; i++)
{
var p = particles[i];
//Updating X and Y coordinates
//We will add 1 to the cos function to prevent negative values which will lead flakes to move upwards
//Every particle has its own density which can be used to make the downward movement different for each flake
//Lets make it more random by adding in the radius
p.y += Math.cos(angle+p.d) + 1 + p.r/2;
p.x += Math.sin(angle) * 2;
//Sending flakes back from the top when it exits
//Lets make it a bit more organic and let flakes enter from the left and right also.
if(p.x > W+5 || p.x < -5 || p.y > H)
{
if(i%3 > 0) //66.67% of the flakes
{
particles[i] = {x: Math.random()*W, y: -10, r: p.r, d: p.d};
}
else
{
//If the flake is exitting from the right
if(Math.sin(angle) > 0)
{
//Enter from the left
particles[i] = {x: -5, y: Math.random()*H, r: p.r, d: p.d};
}
else
{
//Enter from the right
particles[i] = {x: W+5, y: Math.random()*H, r: p.r, d: p.d};
}
}
}
}
}
//animation loop
setInterval(draw, 33);
} * {margin: 0; padding: 0;}
body {
/*You can use any kind of background here.*/
background: #6b92b9;
}
canvas {
display: block;
position: absolute;
} <canvas id="canvas">
<header> <a href = "/games/"><img id="headerimg" src="http://hosted-it.co.uk/img/logo-colour.svg" alt="Hosted-IT" height="150px" width="250px" /> </a></header>
<nav class="navbar"><form method="get" action="/games/questions">
<button type="onclick">Questions</button>
</form> </nav>
<body>
{% block content %}
{% endblock %}
</body>
</canvas>如果有帮助，这都是内联脚本/html/css。它使用 DJango 模板来使用主 html 文件来存储主要格式，然后在各个文件中进行任何其他调整。我希望是否有人能帮我弄清楚为什么 canvas 标签会完全覆盖页面本身的所有内容？
最佳答案
你应该提供一个 plunker，但现在你可以尝试下面的 css
canvas {
display: block;
position: relative;
}
将位置更改为“相对”。可能会奏效。 在 HTML 中第一行关闭画布标签
<canvas id="canvas"></canvas>
<header> <a href = "/games/"><img id="headerimg" src="http://hosted-it.co.uk/img/logo-colour.svg" alt="Hosted-IT" height="150px" width="250px" /></a></header>
<nav class="navbar"><form method="get" action="/games/questions">
<button type="onclick">Questions</button>
</form> </nav>
<body>
{% block content %}
{% endblock %}
</body>
关于javascript - HTML Canvas 显示我的主要内容，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/41060423/