Question

我画了一个画布，里面有一些落下的五彩纸屑，我用这个jquery改变它的高度：

$(window).on("scroll touchmove", function () {
    $('#world').toggleClass('tiny', $(document).scrollTop() > 0);
});

但画布只是拉伸而不是裁剪，所以五彩纸屑看起来很怪异。那是我的纸屑：

(function() {
  var COLORS, Confetti, NUM_CONFETTI, PI_2, canvas, confetti, context, drawCircle, i, range, resizeWindow, xpos;

  NUM_CONFETTI = 350;
  COLORS = [[85, 71, 106], [174, 61, 99], [219, 56, 83], [244, 92, 68], [248, 182, 70]];
  PI_2 = 2 * Math.PI;
  canvas = document.getElementById("world");
  context = canvas.getContext("2d");
  window.w = 0;
  window.h = 0;
  resizeWindow = function() {
    window.w = canvas.width = window.innerWidth;
    return window.h = canvas.height = window.innerHeight;
  };
  window.addEventListener('resize', resizeWindow, false);
  window.onload = function() {
    return setTimeout(resizeWindow, 0);
  };
  range = function(a, b) {
    return (b - a) * Math.random() + a;
  };
  drawCircle = function(x, y, r, style) {
    context.beginPath();
    context.arc(x, y, r, 0, PI_2, false);
    context.fillStyle = style;
    return context.fill();
  };
  xpos = 0.5;
  document.onmousemove = function(e) {
    return xpos = e.pageX / w;
  };
  window.requestAnimationFrame = (function() {
    return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function(callback) {
      return window.setTimeout(callback, 1000 / 60);
    };
  })();
  Confetti = (function() {
    function Confetti() {
      this.style = COLORS[~~range(0, 5)];
      this.rgb = "rgba(" + this.style[0] + "," + this.style[1] + "," + this.style[2];
      this.r = ~~range(2, 6);
      this.r2 = 2 * this.r;
      this.replace();
    }
    Confetti.prototype.replace = function() {
      this.opacity = 0;
      this.dop = 0.03 * range(1, 4);
      this.x = range(-this.r2, w - this.r2);
      this.y = range(-20, h - this.r2);
      this.xmax = w - this.r;
      this.ymax = h - this.r;
      this.vx = range(0, 2) + 8 * xpos - 5;
      return this.vy = 0.7 * this.r + range(-1, 1);
    };
    Confetti.prototype.draw = function() {
      var ref;
      this.x += this.vx;
      this.y += this.vy;
      this.opacity += this.dop;
      if (this.opacity > 1) {
        this.opacity = 1;
        this.dop *= -1;
      }
      if (this.opacity < 0 || this.y > this.ymax) {
        this.replace();
      }
      if (!((0 < (ref = this.x) && ref < this.xmax))) {
        this.x = (this.x + this.xmax) % this.xmax;
      }
      return drawCircle(~~this.x, ~~this.y, this.r, this.rgb + "," + this.opacity + ")");
    };
    return Confetti;
  })();
  confetti = (function() {
    var j, ref, results;
    results = [];
    for (i = j = 1, ref = NUM_CONFETTI; 1 <= ref ? j <= ref : j >= ref; i = 1 <= ref ? ++j : --j) {
      results.push(new Confetti);
    }
    return results;
  })();
  window.step = function() {
    var c, j, len, results;
    requestAnimationFrame(step);
    context.clearRect(0, 0, w, h);
    results = [];
    for (j = 0, len = confetti.length; j < len; j++) {
      c = confetti[j];
      results.push(c.draw());
    }
    return results;
  };
  step();
}).call(this);

另一个问题是五彩纸屑开始从顶部掉下来。但是我希望他们已经填满了整个画布。这有可能吗？

Answer 1

问题在于，当您的画布尝试检测window.resize事件时，动画不会更改窗口的大小。相反，它只是收缩画布的包装，这使得动画很奇怪。我认为你要做的是将overflow: hidden;添加到画布容器的CSS中，这样当它改变大小时，里面的画布可以保持其大小（通过height: __px;规则画布）。

希望这会有所帮助：JSFiddle demo

您可以删除window.resize的监听器。

编辑 - overflow: hidden;不起作用：

只需从画布中删除规则position: fixed;和height: 100%;即可。在页面加载时，画布已调整为正确的大小并保持在正确的位置。定位元素将显示在静态定位的元素上。删除这两个样式，一切都应该像在JSFiddle中一样。

画布拉伸而不是裁剪和开始位置

1 个答案: