无缝四分之一圆和半圆背景效果-html代码-BFW代码库

无缝四分之一圆和半圆背景效果

代码语言：html

所属分类：背景

代码描述：无缝四分之一圆和半圆背景效果

下面为部分代码预览，完整代码请点击下载或在bfwstudio webide中打开

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">

<style>
body {
  font-family: Arial, Helvetica, "Liberation Sans", FreeSans, sans-serif;
  background-color: #000;
  color: #fff;
  margin: 0;
  padding: 0;
  border-width:0;
  cursor:pointer;
}
</style>

</head>
<body translate="no">


<script>
"use strict";

/* Inspired by Johan Karlsson'n pen Quarter Circle and Half a Circle
              https://codepen.io/DonKarlssonSan/details/abvRErd
              vertices are numberered 0 (NW), 1(NE), 2(SE) and 3(SW)
              sides are numered 0(N), 1(E), 2(S) and 3(W)
              */
window.onload = function () {

  const sideMin = 50;
  const sideMax = 120;

  let canv, ctx; // canvas and context
  let maxx, maxy;
  let side; // side of square
  let nbx, nby; // number of squares in width / height
  let orgx, orgy; // coordinates of top left corner of grid[0][0]
  let grid;
  let colors;

  /* for animation */
  let events = [];

  // shortcuts for Math.…

  const mrandom = Math.random;
  const mfloor = Math.floor;
  const mround = Math.round;
  const mceil = Math.ceil;
  const mabs = Math.abs;
  const mmin = Math.min;
  const mmax = Math.max;

  const mPI = Math.PI;
  const mPIS2 = Math.PI / 2;
  const m2PI = Math.PI * 2;
  const msin = Math.sin;
  const mcos = Math.cos;
  const matan2 = Math.atan2;

  const mhypot = Math.hypot;
  const msqrt = Math.sqrt;

  const rac3 = msqrt(3);
  const rac3s2 = rac3 / 2;
  const mPIS3 = Math.PI / 3;

  //-----------------------------------------------------------------

  function intAlea(min, max) {
    // random integer number [min..max[ . If no max is provided, [0..min[

    if (typeof max == 'undefined') {
      max = min;min = 0;
    }
    return mfloor(min + (max - min) * mrandom());
  } // intAlea

  //-----------------------------------------------------------------

  function createGrid() {
    /* attribute color 0, 1 or 2 to every square side
                         so that :
                           - each square uses the 3 colors (two are use once, one is used twice
                           on sides of a same vertex)
                           - matching sides of neighbour square are the same color
                         */

    let elem;
    grid = [];
    for (let ky = 0; ky < nby; ++ky) {
      grid[ky] = [];
      for (let kx = 0; kx < nbx; ++kx) {

        grid[ky][kx] = elem = [];
        // copy constraint from neighbours
        if (ky > 0) elem[0] = grid[ky - 1][kx][2];
        if (kx > 0) elem[3] = grid[ky][kx - 1][1];
        // fill two first sides in not constrained
        if (elem[0] === undefined) elem[0] = intAlea(3);
        if (elem[3] === undefined) elem[3] = intAlea(3);
        // if equal, give other possible values to other sides
        if (elem[0] == elem[3]) {
          let a = (elem[0] + 1) % 3;
          let b = (elem[0] + 2) % 3;
          if (intAlea(2)) {
            elem[1] = a;elem[2] = b;
          } else {
            elem[2] = a;elem[1] = b;
          }
        } else {// two first sides different
          // pick thirs value
          let ov = 0;
          while (ov == elem[0] || ov == elem[3]) ++ov;
          // pick value to use twice
          let tut = intAlea(3);
          if (tut == ov) {
            elem[1] = elem[2] = tut;
          } else {
            if (tut == elem[3]) {
              elem[2] = tut; // same as on side 3
              elem[1] = ov; // other color
            } else {
              elem[1] = tut; // same as on side 0
              elem[2] = ov; // other color
            }
          }

        } // if two first sides different
      } // kx
    } // ky
  } // createGrid

  //---------------------------------.........完整代码请登录后点击上方下载按钮下载查看