JavaScript
语言：
JaveScriptBabelCoffeeScript
确定
const canvas = document.querySelector('#draw');
const ctx = canvas.getContext('2d');
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
ctx.strokeStyle = '#BADA55'; //ctx is the canvas
ctx.lineJoin = 'round';
ctx.lineCap = 'round';
ctx.lineWidth = 100;
// ctx.globalCompositeOperation = 'multiply';
let isDrawing = false;
let lastX = 0;
let lastY = 0;
let hue = 0;
let direction = true;
function draw(e) {
if (!isDrawing) return; // stop the fn from running when they are not moused down
console.log(e);
ctx.strokeStyle = `hsl(${hue}, 100%, 50%)`;
ctx.beginPath();
// start from
ctx.moveTo(lastX, lastY);
// go to
ctx.lineTo(e.offsetX, e.offsetY);
ctx.stroke();
[lastX, lastY] = [e.offsetX, e.offsetY];
hue++;
if (hue >= 360) {
hue = 0;
}
if (ctx.lineWidth >= 100 || ctx.lineWidth <= 1) {
direction = !direction;
}
if (direction) {
ctx.lineWidth++;
} else {
ctx.lineWidth--;
}
}
canvas.addEventListener('mousedown', (e) => {
isDrawing = true;
[lastX, lastY] = [e.offsetX, e.offsetY];
});
canvas.addEventListener('mousemove', draw);
canvas.addEventListener('mouseup', () => isDrawing = false);
canvas.addEventListener('mouseout', () => isDrawing = false);
