Sukar untuk dijelaskan. Tetapi saya akan cuba, keseluruhan kanvas diimbangi. Saya tidak pasti bagaimana ini berlaku atau bagaimana untuk membetulkannya. Seperti apabila tetikus anda berada di sudut kiri atas halaman dan anda bermula dari tengah, ia sepadan dengan sudut kiri atas elemen kanvas itu sendiri. Gunakan coretan kod untuk memahami perkara yang saya perkatakan.

let currentColor = null;

let inputs = document.getElementsByClassName("style2");

for (const input of inputs) {
  input.addEventListener("click", (e) => {
    if (e.detail !== 2) e.preventDefault();
  });
}


let arr = [];

for (let i = 0; i < inputs.length + 1; i++) {
  arr.push(i.toString());
}
arr.shift();

for (const input of inputs) {
  input.addEventListener("input", (e) => {
    const { value } = document.getElementById(e.target.id);
    currentColor = value;
    $("#selectedColor").css("background-color", value);
  })
    input.addEventListener("click", (e) => {
    const { value }  = document.getElementById(e.target.id);
    currentColor = value;
    $("#selectedColor").css("background-color", value);
  })
}

var rangeslider = document.getElementById("sliderRange");
const setSize = document.getElementById("setSize")
const submit = document.getElementById("submit")

submit.addEventListener("click", (e) => {
  rangeslider.value = setSize.value 
})

const button = document.getElementById("clear")
// create canvas element and append it to document body
var canvas = document.getElementById('canvas');
// some hotfixes... ( ≖_≖)
// get canvas 2D context and set him correct size
var ctx = canvas.getContext('2d');
resize();

// last known position
var pos = { x: 0, y: 0 };

window.addEventListener('resize', resize);
button.addEventListener('click', clear)
document.addEventListener('mousemove', draw);
document.addEventListener('mousedown', setPosition);
document.addEventListener('mousemove', setPosition);


// new position from mouse event
function setPosition(e) {
  let canvas = document.getElementById("canvas")
  pos.x = e.clientX
  pos.y = e.clientY
}

// resize canvas
function resize() {
  ctx.canvas.width = 650;
  ctx.canvas.height = 375;
}

function draw(e) {
  // mouse left button must be pressed
  if (e.buttons !== 1) return;
  let canvas = document.getElementById('canvas');

  console.log(pos)
  ctx.beginPath(); // begin

  ctx.lineWidth = rangeslider.value;
  ctx.lineCap = 'round';
  ctx.strokeStyle = currentColor;

  ctx.moveTo(pos.x, pos.y); // from
  setPosition(e);
  ctx.lineTo(pos.x, pos.y); // to

  ctx.stroke(); // draw it!
}

function clear() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
}

html, body {
  height: 100%;
  width: 100%;
  font-family: sans-serif;
  background-color: #B3B7B5;
/*   overflow: hidden; */
}

.style2 {
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
  background-color: transparent;
  width: 35px;
  height: 35px;
  border: none;
  cursor: pointer;
}


.style2::-webkit-color-swatch {
  border-radius: 50%;
  border: 3px solid #000000;
}
.style2::-moz-color-swatch {
  border-radius: 50%;
  border: 3px solid #000000;
}

.box {
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: 5px;
  max-width: 320px;
  margin: 0 auto;
  padding: 7.5px 10px;
}

.box1 {
    display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: 5px;
  max-width: 9999px;
  margin: 0 auto;
  padding: 10px 10px;
}

.box5 {
    display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: 5px;
  max-width: 650px;
  margin: 0 auto;
  padding: 10px 10px;
}

.box2 {
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: 5px;
  max-width: 9999px;
  margin: 0 auto;
  padding: 10px 10px;
}

#selectedColor {
  width: 100px;
  height: 30px;
  border: 3px solid black;
  border-radius: 5px;
  background-color: black;
}

.canvas {
  height: 350px;
  width: 650px;
  border: 3px solid black;
  border-radius: 5px;
  background-color: white;
  cursor: crosshair;
  position: relative;
/*   left: 50%; */
}

#clear {
  width: 50px;
  height: 35px;
  font-size: 15px;
  border-radius: 5px;
}

#submit {
  width: 59px;
  height: 23px;
  margin: auto;
  left: 35%;
  border-radius: 5px;
  position: relative;
}

.rangeslider {
    width: 50%;
}
  
.myslider {
    -webkit-appearance: none;
    background: #FCF3CF  ;
    width: 50%;
    height: 20px;
    opacity: 2;
   }
  
  
.myslider::-webkit-slider-thumb {
    -webkit-appearance: none;
    cursor: pointer;
    background: #34495E  ;
    width: 5%;
    height: 20px;
}
  
  
.myslider:hover {
    opacity: 1;
}

.rangeslider {
  left: 38%;
  position: absolute;
}

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>replit</title>
  <link href="style.css" rel="stylesheet" type="text/css" />
</head>

<body>
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

  <div class="box5">
    <canvas class="canvas" id="canvas"></canvas>
  </div>
  
  <div class="box1">
    <button id="clear">Clear</button><br>
  </div>

  <div class="box1">
    <div class="rangeslider">
          <input type="range" min="1" max="100" value="5" class="myslider" id="sliderRange">
    </div>
  </div>
  <div class=box1>
    <div>
      <input id="setSize" type="text" placeholder="Set Brush Size... (Max 100)">
      <br>
      <button type="submit" id="submit" for="setSize">Submit</button>
    </div>
  </div>
  
  <div class="box">
      <div class="container">
        <input type="color" value="#000000" class="style2" id="1" />
      </div>
      <div class="container">
        <input type="color" value="#ffffff" class="style2" id="2" />
      </div>
      <div class="container">
        <input type="color" value="#ffffff" class="style2" id="3" />
      </div>
      <div class="container">
        <input type="color" value="#ffffff" class="style2" id="4" />
      </div>
      <div class="container">
        <input type="color" value="#ffffff" class="style2" id="5" />
      </div>
  </div>

  <div class="box">
    <label for="selectedColor">Current Color:</label>
    <div id="selectedColor"></div>
  </div>

  <script src="script.js"></script>
</body>

</html>
 

Saya tahu kod ini agak pelik, tetapi sila beritahu saya.