javascript - 如何旋转形状？

Question

到目前为止我得到了什么:

我可以使用一些简单的语法将形状绘制到 Canvas 中:

let shape = "10n10" // example shapeSyntax (*)



shapeSyntax:  "1" == "colored area"
              "0" == "blank area"
              "n" == "new line"


* So creating a simple line (width = 4, height = 1) is possible using the syntax "1111"
* Creating a square (width = 2, height = 2) is possible using the syntax "11n11" (n stands for new line)
* Creating a stair -shape would be possible using the syntax "001n011n111"

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到目前为止，这工作得很好。 所以我添加了代码，以便您查看自己的代码:

我想得到什么:

我想开发一个 rotate(degree) 函数，它能够旋转语法(不仅仅是 Canvas 元素或其他东西!! !) 围绕 [90, 180, 270] 度的任何形状。

因此将语法为“1111”的行旋转大约 90deg 应该得到“1n1n1n1”:

rotate("1111", 90) // == "1n1n1n1"

请看这张图片，我很确定它会有助于理解:

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What I've noticed is that rotating any shape around 180deg the syntax could just be changed by reading it backwards: "1011" gets "1101". But how can I get the syntax from 0->90deg? I got no idea how so any help how to solve this would be really appreciated. Thanks in advance.

// This is what I've got

// The 4 shapes where
// "1" == "colored area"
// "0" == "blank area"
// "n" == "new line"
let shapeA = "1111"
let shapeB = "10n11"
let shapeC = "111n011"
let shapeD = "00111n11100"


// This is the function to draw the shapes using *canvas*
let drawShape = function(shape, offset) {
  shape = shape.split("n");
  let shapeHeight = shape.length,
      shapeWidth = shape[0].length;
      
  let canvas = document.createElement("canvas");
  let ctx = canvas.getContext("2d");
  canvas.width = canvas.height = 300;
  ctx.fillStyle=["red", "green", "blue", "gray", "magenta", "orange", "yellow"][Math.round(Math.random()*6)];
  
  for (let y=0; y<shapeHeight; y++) {
    for (let x=0; x<shapeWidth; x++) {
      if (shape[y][x] === "1") 
        ctx.fillRect(x*20, y*20, 20, 20);
    }
  }
  canvas.style.position = "absolute";
  canvas.style.left = offset + "%";
  document.getElementById("element").append(canvas)
}


// This is how I'm able to call the function (the second parameter is for the offset of the position)
drawShape(shapeA, 0);
drawShape(shapeB, 20);
drawShape(shapeC, 40);
drawShape(shapeD, 60);

input {
position: absolute;
  top: 50%;
  z-index: 4
} 

<input type="text" oninput="document.getElementById('element').innerHTML = ''; drawShape(this.value, 10)" placeholder="input shape syntax"/>
<div id="element"></div>

Answer 1

转换成二维数组，旋转(transpose)然后转换回来。

编辑:谢谢 meowgoesthedog，转置并不代表我认为的意思。

var rotate = array => array[0].map( (col, i) => array.map(row => row[i]).reverse() );
var decode = str => str.split('n').map( s => s.split('') )
var encode = arr => arr.map( a => a.join('') ).join('n')

encode( rotate( decode( '01n00' ) ) )