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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Canvas Rotation</title>
<style>
html{
background-color: #999;
}
#canvas{
background-color: #fff;
border: 1px solid #333;
width: 70%;
margin: 1rem auto;
display: block;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
<script>
let canvas, ctx;
document.addEventListener('DOMContentLoaded', ()=>{
canvas = document.getElementById('canvas');
ctx = canvas.getContext('2d');
canvas.width = 600;
canvas.height = 800;
ctx.fillStyle = 'cornflowerblue';
ctx.strokeStyle = '#ccc';
ctx.lineWidth = 2;
ctx.textAlign = 'start';
ctx.font = 'normal 30px Arial';
drawGrid(100);
let x = 100;
let y = 100;
ctx.save(); //creates a save point
ctx.beginPath();
ctx.translate(200, 200);
ctx.fillText('translate', 10, 30);
ctx.fill();
ctx.closePath();
ctx.restore(); //go back to the last save point
ctx.save();
ctx.beginPath();
ctx.arc(0, 0, 10, 0, Math.PI*2);
ctx.rotate(Math.PI/4); //3.14 radians 180 deg
ctx.fillText('rotate', 300, 0);
ctx.fill();
ctx.closePath();
ctx.restore();
ctx.beginPath();
ctx.translate(100, 500);
ctx.scale(1, -1);
ctx.fillText('scale', x, y);
ctx.fill();
ctx.closePath();
});
function drawGrid(gap){
ctx.beginPath();
for(x=gap; x<canvas.width; x=x+gap){
ctx.moveTo(x, 0);
ctx.lineTo(x, canvas.height);
}
for(let y=gap; y<canvas.height; y=y+gap){
ctx.moveTo(0, y);
ctx.lineTo(canvas.height, y);
}
ctx.stroke();
ctx.closePath();
}
</script>
</body>
</html>
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