How to Resize an Image using Client-Side JavaScript and HTML5 Canvas

Output image preserves its aspect ratios and resolution. Enables image export. Full code implementation included.

Illustration by Author | Resizing an image using pure JavaScript

For the past couple of months, several browser utility tools I have implemented for a variety of distinct use-cases have involved the use of HTML5 element — <canvas></canvas>

FYI: For more information on HTML <canvas> component, please refer to: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/canvas

In essence, the unique attributes and in-built functions of the <canvas> element paves the way for web-based multimedia use-cases. On a smaller scale, <canvas> is able to render image data via the function drawImage() which in turn can be resized while preserving its aspect ratio. With this property in mind, I decided to create a minimalistic browser tool as an offline alternative to resize any user-uploaded image and enable the export of its resized output.

Implementation Details — 3 Parts

Image by Author | Each of the 3 implementation steps refer to the specific numbered components as tagged in the above screenshot

Part (1). Enable users to upload custom…