Javascript线条动态背景Canvas

发布 : 2019-04-10 分类 : WEB 浏览 :

效果预览

源代码

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! function() {
//封装方法,压缩之后减少文件大小
function get_attribute(node, attr, default_value) {
return node.getAttribute(attr) || default_value;
}
//封装方法,压缩之后减少文件大小
function get_by_tagname(name) {
return document.getElementsByTagName(name);
}
//获取配置参数
function get_config_option() {
var scripts = get_by_tagname("script"),
script_len = scripts.length,
script = scripts[script_len - 1]; //当前加载的script
return {
l: script_len, //长度,用于生成id用
z: get_attribute(script, "zIndex", -20), //z-index
o: get_attribute(script, "opacity", 0.7), //opacity
c: get_attribute(script, "color", "0,100,150"), //color
n: get_attribute(script, "count", 130) //count
};
}
//设置canvas的高宽
function set_canvas_size() {
canvas_width = the_canvas.width = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth,
canvas_height = the_canvas.height = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight;
}

//绘制过程
function draw_canvas() {
context.clearRect(0, 0, canvas_width, canvas_height);
//随机的线条和当前位置联合数组
var all_array = [current_point].concat(random_lines);
var e, i, d, x_dist, y_dist, dist; //临时节点
//遍历处理每一个点
random_lines.forEach(function(r) {
r.x += r.xa,
r.y += r.ya, //移动
r.xa *= r.x > canvas_width || r.x < 0 ? -1 : 1,
r.ya *= r.y > canvas_height || r.y < 0 ? -1 : 1, //碰到边界,反向反弹
context.fillRect(r.x - 0.5, r.y - 0.5, 1, 1); //绘制一个宽高为1的点
for (i = 0; i < all_array.length; i++) {
e = all_array[i];
//不是当前点
if (r !== e && null !== e.x && null !== e.y) {
x_dist = r.x - e.x, //x轴距离 l
y_dist = r.y - e.y, //y轴距离 n
dist = x_dist * x_dist + y_dist * y_dist; //总距离, m
dist < e.max && (e === current_point && dist >= e.max / 2 && (r.x -= 0.03 * x_dist, r.y -= 0.03 * y_dist), //靠近的时候加速
d = (e.max - dist) / e.max,
context.beginPath(),
context.lineWidth = d / 2,
context.strokeStyle = "rgba(" + config.c + "," + (d + 0.2) + ")",
context.moveTo(r.x, r.y),
context.lineTo(e.x, e.y),
context.stroke());
}
}
all_array.splice(all_array.indexOf(r), 1);

}), frame_func(draw_canvas);
}
//创建画布,并添加到body中
var the_canvas = document.createElement("canvas"), //画布
config = get_config_option(), //配置
canvas_id = "c_n" + config.l, //canvas id
context = the_canvas.getContext("2d"),
canvas_width, canvas_height,
frame_func = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function(func) {
window.setTimeout(func, 1000 / 45);
},
random = Math.random,
current_point = {
x: null, //当前鼠标x
y: null, //当前鼠标y
max: 20000
};
the_canvas.id = canvas_id;
the_canvas.style.cssText = "position:fixed;top:0;left:0;z-index:" + config.z + ";opacity:" + config.o;
get_by_tagname("body")[0].appendChild(the_canvas);

//初始化画布大小
set_canvas_size(), window.onresize = set_canvas_size;

//当时鼠标位置存储,离开的时候,释放当前位置信息
window.onmousemove = function(e) {
e = e || window.event, current_point.x = e.clientX, current_point.y = e.clientY;
}, window.onmouseout = function() {
current_point.x = null, current_point.y = null;
};

//随机生成config.n条线位置信息
for (var random_lines = [], i = 0; config.n > i; i++) {
var x = random() * canvas_width, //随机位置
y = random() * canvas_height,
xa = 2 * random() - 1, //随机运动方向
ya = 2 * random() - 1;
random_lines.push({
x: x,
y: y,
xa: xa,
ya: ya,
max: 6000 //沾附距离
});
}

//0.1秒后绘制
setTimeout(function() {
draw_canvas();
}, 100);
}();
本文作者 : Richex
原文链接 : https://blog.richex.cn/524.html
版权声明 : 本博客所有文章除特别声明外,均采用 CC BY-NC-SA 4.0 许可协议。转载请注明出处!

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