我正在编写一段代码,希望在刷新时更改可擦画布的颜色。
在CSS中触发颜色会更容易,尽管现在这是在这些触发器的编码本身中进行的;
var container = document.getElementById('canvas');
init(container, 5000, 3000, '#f8fa58');
我如何使它可以从中选择多种(假设2种)可变颜色。因此,在刷新网站时,特定颜色是随机的吗?
(function() {
// a little verbose but...
function handleMousemove(event) {
var x = event.clientX;
var y = event.clientY;
draw(x, y);
}
function handleTouchmove(event) {
event.preventDefault(); // we don't want to scroll
var touch = event.touches[0];
var x = touch.clientX;
var y = touch.clientY;
draw(x, y);
}
// this one can be shared by both touch and move events
function activateDrawing(event) {
event.preventDefault();
canvas.isDrawing = true;
}
function draw(eventX, eventY) {
var x = eventX - canvas.node.offsetLeft;
var y = eventY - canvas.node.offsetTop;
if (!canvas.isDrawing) {
return;
}
var radius = 100; // or whatever
var fillColor = '#ff0000';
ctx.globalCompositeOperation = 'destination-out';
ctx.fillCircle(x, y, radius, fillColor);
}
function createCanvas(parent, width, height) {
var canvas = {};
canvas.node = document.createElement('canvas');
canvas.context = canvas.node.getContext('2d');
canvas.node.width = width || 100;
canvas.node.height = height || 100;
parent.appendChild(canvas.node);
return canvas;
}
var canvas, ctx; // got it out to avoid nesting too deeply my handlers;
function init(container, width, height, fillColor) {
canvas = createCanvas(container, width, height);
ctx = canvas.context;
// define a custom fillCircle method
ctx.fillCircle = function(x, y, radius, fillColor) {
var radgrad = ctx.createRadialGradient(x, y, 0, x, y, radius);
radgrad.addColorStop(0, 'rgba(255,0,0,1)');
radgrad.addColorStop(0.8, 'rgba(255,0,0,.9)');
radgrad.addColorStop(1, 'rgba(255,0,0,0)');
// draw shape
ctx.fillStyle = radgrad;
ctx.fillRect(x - radius, y - radius, x + radius, y + radius);
};
ctx.clearTo = function(fillColor) {
ctx.fillStyle = fillColor;
ctx.fillRect(0, 1, width, height);
};
ctx.clearTo(fillColor || "#ddd");
// bind mouse events
canvas.node.onmousemove = throttle(handleMousemove);
canvas.node.ontouchmove = throttle(handleTouchmove);
canvas.node.onmouseenter =
canvas.node.ontouchstart = throttle(activateDrawing);
}
var container = document.getElementById('canvas');
init(container, 5000, 3000, '#f8fa58');
/* Bonus : throttle these events so they don't fire too often */
function throttle(callback) {
var active = false; // a simple flag
var evt; // to keep track of the last event
var handler = function() { // fired only when screen has refreshed
active = false; // release our flag
callback(evt);
}
return function handleEvent(e) { // the actual event handler
evt = e; // save our event at each call
if (!active) { // only if we weren't already doing it
active = true; // raise the flag
requestAnimationFrame(handler); // wait for next screen refresh
};
}
}
})();
document.body.addEventListener('touchstart', function(e) {
e.preventDefault();
});
body {
overflow: hidden !important;
margin-left: -10vw;
margin-top: -30vh;
}
#back {
z-index: -10;
pointer-events: none;
position: absolute;
margin: 0;
display: block;
background: url(https://odlp-staging1.s3.amazonaws.com/uploads/2012/04/original_01_-belladonna-viviane-sassen-jpg.jpg) no-repeat center center fixed;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;
width: 110vw;
height: 130vh;
}
#canvas {
z-index: -1;
top: 2vh;
left: -10vw;
width: 110vw;
height: 130vh;
overflow: hidden;
}
<div id="back"></div>
<div id="canvas"></div>
最佳答案
对于随机颜色,可以将各种颜色存储在数组中,然后使用随机方法。
var randomColors = ['#f8fa58','red','black'];
var bg = randomColors[Math.floor(Math.random()*randomColors.length)];
init(container, 5000, 3000, bg);
关于javascript - 在刷新浏览器时更改JS中的颜色,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/46911095/