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canvas.js
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canvas.js
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let drawColour = "black";
let drawWidth = 5;
let whiteboardColour = "white";
window.addEventListener("resize", resizeCanvas, false);
function resizeCanvas() {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight - 100;
context.lineJoin = "round";
context.lineCap = "round";
if (index > -1) {
context.putImageData(undoStack[index], 0, 0);
}
}
// Select Pen Colour
function changeColour(element) {
drawColour = element.style.background;
}
function clearCanvas() {
context.fillStyle = whiteboardColour;
context.clearRect(0, 0, canvas.width, canvas.height);
context.fillRect(0, 0, canvas.width, canvas.height);
undoStack = [];
index = -1;
}
let undoStack = [];
let redoStack = [];
let index = -1;
function undoLast() {
if (index <= 0) {
redoStack.push(undoStack.pop());
clearCanvas();
} else {
index -= 1;
redoStack.push(undoStack.pop());
context.putImageData(undoStack[index], 0, 0);
}
console.log("undo stack:", undoStack);
console.log("redo stack: ", redoStack);
}
// Keybindings for undo and redo
Mousetrap.bind(["ctrl+z", "command+z"], function () {
undoLast();
});
Mousetrap.bind(["ctrl+shift+z", "command+shift+z"], function () {
redoLast();
});
function redoLast() {
if (redoStack.length != 0) {
undoStack.push(redoStack.pop());
index += 1;
console.log(redoStack);
context.putImageData(undoStack[index], 0, 0);
}
}
const canvas = document.querySelector("#canvas");
const context = canvas.getContext("2d");
canvas.height = window.innerHeight - 100;
canvas.width = window.innerWidth;
context.fillStyle = whiteboardColour;
context.fillRect(0, 0, canvas.width, canvas.height);
let isDown = false;
let points = [];
let beginPoint = null;
context.lineJoin = "round";
context.lineCap = "round";
canvas.addEventListener("mousedown", down, false);
canvas.addEventListener("mousemove", move, false);
canvas.addEventListener("mouseup", up, false);
canvas.addEventListener("mouseout", up, false);
function down(evt) {
isDown = true;
const { x, y } = getPos(evt);
points.push({ x, y });
beginPoint = { x, y };
drawLine(beginPoint, beginPoint, beginPoint);
}
function move(evt) {
if (!isDown) return;
const { x, y } = getPos(evt);
points.push({ x, y });
if (points.length > 3) {
const lastTwoPoints = points.slice(-2);
const controlPoint = lastTwoPoints[0];
const endPoint = {
x: (lastTwoPoints[0].x + lastTwoPoints[1].x) / 2,
y: (lastTwoPoints[0].y + lastTwoPoints[1].y) / 2,
};
drawLine(beginPoint, controlPoint, endPoint);
beginPoint = endPoint;
}
}
function up(evt) {
if (!isDown) return;
const { x, y } = getPos(evt);
points.push({ x, y });
if (points.length > 3) {
const lastTwoPoints = points.slice(-2);
const controlPoint = lastTwoPoints[0];
const endPoint = lastTwoPoints[1];
drawLine(beginPoint, controlPoint, endPoint);
}
beginPoint = null;
isDown = false;
points = [];
undoStack.push(context.getImageData(0, 0, canvas.width, canvas.height));
index += 1;
redoStack = [];
console.log("undoStack: ", undoStack);
console.log("redoStack: ", redoStack);
}
function getPos(evt) {
return {
x: evt.clientX,
y: evt.clientY,
};
}
function drawLine(beginPoint, controlPoint, endPoint) {
context.beginPath();
context.lineWidth = drawWidth;
context.strokeStyle = drawColour;
context.moveTo(beginPoint.x, beginPoint.y);
context.quadraticCurveTo(
controlPoint.x,
controlPoint.y,
endPoint.x,
endPoint.y
);
context.stroke();
context.closePath();
}