PHP 및 GD 라이브러리 가이드: 마우스를 기반으로 그래픽을 그리는 방법

<?php
$width = 600;
$height = 400;

$image = imagecreatetruecolor($width, $height);
$backgroundColor = imagecolorallocate($image, 255, 255, 255);
imagefill($image, 0, 0, $backgroundColor);

<canvas id="canvas" width="<?php echo $width; ?>" height="<?php echo $height; ?>"></canvas>
<script>
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var isDrawing = false;
var lastX = 0;
var lastY = 0;

canvas.onmousedown = function(e) {
  isDrawing = true;
  lastX = e.clientX - canvas.offsetLeft;
  lastY = e.clientY - canvas.offsetTop;
};

canvas.onmousemove = function(e) {
  if (!isDrawing) return;
  var x = e.clientX - canvas.offsetLeft;
  var y = e.clientY - canvas.offsetTop;
  
  // 向服务器端发送鼠标坐标
  var xmlhttp = new XMLHttpRequest();
  xmlhttp.open("GET", "draw.php?x=" + x + "&y=" + y, true);
  xmlhttp.send();
  
  context.beginPath();
  context.moveTo(lastX, lastY);
  context.lineTo(x, y);
  context.stroke();
  
  lastX = x;
  lastY = y;
};

canvas.onmouseup = function() {
  isDrawing = false;
};
</script>

<?php
$x = $_GET['x'];
$y = $_GET['y'];

<?php
imagefilledellipse($image, $x, $y, 10, 10, imagecolorallocate($image, 0, 0, 0));

<?php
header('Content-Type: image/png');
imagepng($image);
imagedestroy($image);

<?php
$width = 600;
$height = 400;

$image = imagecreatetruecolor($width, $height);
$backgroundColor = imagecolorallocate($image, 255, 255, 255);
imagefill($image, 0, 0, $backgroundColor);

$x = $_GET['x'];
$y = $_GET['y'];

imagefilledellipse($image, $x, $y, 10, 10, imagecolorallocate($image, 0, 0, 0));

header('Content-Type: image/png');
imagepng($image);
imagedestroy($image);
?>