Canvas Composition

Posted in Canvas Tutorial

Updated on May 19, 2024

By Mari Selvan

👁️ 52 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

Canvas is a powerful HTML element that allows dynamic, scriptable rendering of 2D shapes, images, and animations. Understanding how to compose elements on the canvas is essential for creating complex and visually appealing graphics.

In this guide, we'll explore various techniques for composing elements on the HTML canvas.

📦 Layers and Composition

One of the key concepts in canvas composition is layering. By default, canvas has a single drawing surface, but you can simulate layers by drawing elements in a specific order. Elements drawn later appear on top of previously drawn elements, creating the illusion of depth and composition.

✏️ Drawing Order

The order in which elements are drawn on the canvas determines their visibility. Elements drawn later are positioned above earlier ones. For example, drawing a rectangle after a circle will result in the rectangle appearing on top of the circle.

🕶️ Transparency and Opacity

Canvas supports transparency and opacity, allowing elements to blend with the background or other elements. You can control transparency using the globalAlpha property or by specifying RGBA color values with an alpha channel.

📄 Example

Let's create a simple canvas composition:

example.js

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const canvas = document.getElementById('myCanvas');
const ctx = canvas.getContext('2d');

// Draw a blue rectangle
ctx.fillStyle = 'blue';
ctx.fillRect(50, 50, 100, 80);

// Draw a red circle
ctx.fillStyle = 'red';
ctx.beginPath();
ctx.arc(150, 100, 40, 0, 2 * Math.PI);
ctx.fill();

🧠 How it works?

In this example, we draw a blue rectangle and a red circle on the canvas. The rectangle is drawn first, followed by the circle, resulting in the circle appearing on top of the rectangle.