How to write an algorithm for finding the coordinates of the corners of the area of intersection of two rectangles?

M

Michael9002019-10-18 21:39:18

JavaScript

Michael900, 2019-10-18 21:39:18

Confused about it. You need to find the coordinates (lower left and upper right) of the area created by the intersection of two rectangles, and display this area with a red border. What am I doing wrong?

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>new</title>
  </head>
  <body>
    <canvas id="canvas"></canvas>
    <script src="script.js"></script>
  </body>
</html>

const WIDTH = 800;
const HEIGHT = 500;
const canvas = document.getElementById("canvas");
canvas.width = WIDTH;
canvas.height = HEIGHT;
const ctx = canvas.getContext("2d");
ctx.setTransform(1, 0, 0, -1, 0, HEIGHT);
const N = 10;
const array = [];

function rand(min, max) {
  return Math.floor(Math.random() * (max - min)) + min;
}

const r1 = {
  x1: rand(0, WIDTH),
  y1: rand(0, HEIGHT),
  x2: rand(0, WIDTH),
  y2: rand(0, HEIGHT)
};
const r2 = {
  x1: rand(0, WIDTH),
  y1: rand(0, HEIGHT),
  x2: rand(0, WIDTH),
  y2: rand(0, HEIGHT)
};
if (r1.x1 > r1.x2) {
  [r1.x1, r1.x2] = [r1.x2, r1.x1];
}
if (r1.y1 > r1.y2) {
  [r1.y1, r1.y2] = [r1.y2, r1.y1];
}
if (r2.x1 > r2.x2) {
  [r2.x1, r2.x2] = [r2.x2, r2.x1];
}
if (r2.y1 > r2.y2) {
  [r2.y1, r2.y2] = [r2.y2, r2.y1];
}
if (r1.y2 < r2.y1 || r1.y1 > r2.y2 || r1.x2 < r2.x1 || r1.x1 > r2.x2) {
  console.log("не пересекутся");
} else {
  console.log("пересеклись");
  let r3x1 = max(r1.y1, r2.y1),
    r3y1 = max(r1.x1, r2.x1),
    r3x2 = min(r1.y2, r2.y2),
    r3y2 = min(r1.x2, r2.x2);
  ctx.beginPath();
  ctx.strokeStyle = "red";
  ctx.strokeRect(r3x1, r3y1, r3x2 - r3x1, r3x2 - r3y1);

  ctx.beginPath();
  console.log("левый нижний: x = ", r3x1, " y = ", r3y1);
  console.log("правый верхний : x = ", r3x2, " y = ", r3y2);
}
function min(a, b) {
  if (a < b) return a;
  else return b;
}

function max(a, b) {
  if (a > b) return a;
  else return b;
}

ctx.strokeStyle = "grey";
ctx.strokeRect(r1.x1, r1.y1, r1.x2 - r1.x1, r1.y2 - r1.y1);
ctx.strokeRect(r2.x1, r2.y1, r2.x2 - r2.x1, r2.y2 - r2.y1);