<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Canvas</title>
<style>
body {
margin: 0;
overflow: hidden;
background: #ccc;
}
.toolbar {
width: 150px;
height: 75px;
background: #ccc;
padding: 5px;
}
input[type="color"], button {
width: 90%;
margin: 0 auto;
display: block;
}
input[type="range"] {
width: 70%;
}
span {
position: relative;
bottom: 5px;
}
</style>
</head>
<body>
<div class="toolbar">
<input type="color" aria-label="select pen color">
<input type="range" min="2" max="50" value="30" aria-label="select pen size"><span class="output">30</span>
<button>Clear canvas</button>
</div>
<canvas class="myCanvas">
<p>Add suitable fallback here.</p>
</canvas>
<script>
var canvas = document.querySelector('.myCanvas');
var width = canvas.width = window.innerWidth;
var height = canvas.height = window.innerHeight-85;
var ctx = canvas.getContext('2d');
ctx.fillStyle = 'rgb(0,0,0)';
ctx.fillRect(0,0,width,height);
var colorPicker = document.querySelector('input[type="color"]');
var sizePicker = document.querySelector('input[type="range"]');
var output = document.querySelector('.output');
var clearBtn = document.querySelector('button');
// covert degrees to radians
function degToRad(degrees) {
return degrees * Math.PI / 180;
};
// update sizepicker output value
sizePicker.oninput = function() {
output.textContent = sizePicker.value;
}
// store mouse pointer coordinates, and whether the button is pressed
var curX;
var curY;
var pressed = false;
// update mouse pointer coordinates
document.onmousemove = function(e) {
curX = (window.Event) ? e.pageX : e.clientX + (document.documentElement.scrollLeft ? document.documentElement.scrollLeft : document.body.scrollLeft);
curY = (window.Event) ? e.pageY : e.clientY + (document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop);
}
canvas.onmousedown = function() {
pressed = true;
};
canvas.onmouseup = function() {
pressed = false;
}
clearBtn.onclick = function() {
ctx.fillStyle = 'rgb(0,0,0)';
ctx.fillRect(0,0,width,height);
}
function draw() {
if(pressed) {
ctx.fillStyle = colorPicker.value;
ctx.beginPath();
ctx.arc(curX, curY-85, sizePicker.value, degToRad(0), degToRad(360), false);
ctx.fill();
}
requestAnimationFrame(draw);
}
draw();
</script>
</body>
</html>
