JavaScript Project - Drawing Application

 In this tutorial, we will learn how to create a simple JavaScript Drawing Application.

We will use the <canvas> HTML element to draw graphics on a web page.

The <canvas> HTML element is used to draw graphics, on the fly, via JavaScript.

The <canvas> element is only a container for graphics. You must use JavaScript to actually draw the graphics.

The <canvas> tag is a relatively new element that is quickly gaining in popularity. It can be used for a variety of different things, such as drawing graphs, shapes, images, applying styles and colors, making photo compositions, and even some simple, neat animations.

JavaScript Drawing Application

Create a folder called drawing-app as project workspace and we will create all the project files inside this folder.

1. index.html

Let's create index.html and add the following code to it:

<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8" /> <meta name="viewport" content="width=device-width, initial-scale=1.0" /> <title>Drawing App</title> <link rel="stylesheet" href="style.css" /> <script src="script.js" defer></script> </head> <body> <h1> Drawing App </h1> <canvas id="canvas" width="800" height="400"></canvas> <div class="toolbox"> <button id="decrease">-</button> <span id="size">30</span> <button id="increase">+</button> <input type="color" id="color" /> <button id="clear">💩</button> </div> </body> </html>

2. script.js

Let's create JavaScript file named script.js and add following JavaScript code to it:

const canvas = document.getElementById("canvas"); const increaseBtn = document.getElementById("increase"); const decreaseBtn = document.getElementById("decrease"); const sizeEl = document.getElementById("size"); const colorEl = document.getElementById("color"); const clearEl = document.getElementById("clear"); const ctx = canvas.getContext("2d"); let size = 30; let isPressed = false; let color = "black"; let x = undefined; let y = undefined; canvas.addEventListener("mousedown", (e) => { isPressed = true; x = e.offsetX; y = e.offsetY; }); canvas.addEventListener("mouseup", (e) => { isPressed = false; x = undefined; y = undefined; }); canvas.addEventListener("mousemove", (e) => { if (isPressed) { const x2 = e.offsetX; const y2 = e.offsetY; drawCircle(x2, y2); drawLine(x, y, x2, y2); x = x2; y = y2; } }); function drawCircle(x, y) { ctx.beginPath(); ctx.arc(x, y, size, 0, Math.PI * 2); ctx.fillStyle = color; ctx.fill(); } function drawLine(x1, y1, x2, y2) { ctx.beginPath(); ctx.moveTo(x1, y1); ctx.lineTo(x2, y2); ctx.strokeStyle = color; ctx.lineWidth = size * 2; ctx.stroke(); } increaseBtn.addEventListener("click", () => { size += 5; if (size > 50) { size = 50; } updateSizeOnScreen(); }); decreaseBtn.addEventListener("click", () => { size -= 5; if (size < 5) { size = 5; } updateSizeOnScreen(); }); colorEl.addEventListener("change", (e) => { color = e.target.value; }); clearEl.addEventListener("click", () => { ctx.clearRect(0, 0, canvas.width, canvas.height); }); function updateSizeOnScreen() { sizeEl.innerText = size; }

style.css

Let's create CSS file named style.css and add the following CSS code to it:

@import url("https://fonts.googleapis.com/css2?family=Poppins:wght@200;400;600&display=swap"); * { box-sizing: border-box; } body { background-color: #f5f5f5; display: flex; flex-direction: column; align-items: center; justify-content: center; font-family: "Poppins", sans-serif; margin: 0; min-height: 100vh; } canvas { border: 2px solid rebeccapurple; } .toolbox { background-color: rebeccapurple; border: 1px solid rebeccapurple; display: flex; padding: 1rem; width: 804px; } .toolbox > * { background-color: #fff; border: none; display: inline-flex; align-items: center; justify-content: center; font-size: 2rem; padding: 0.25rem; margin: 0.25rem; height: 50px; width: 50px; } .toolbox > *:last-child { margin-left: auto; }

Open index.html in Browser

Let's open the index.html file in the browser and you will be able to see the following screen:

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