Image Resizing on the Client-Side with JavaScript: An Open Source Solution

In today's web development landscape, it's often desirable to resize images on the client-side before uploading them to the server. This approach can optimize image quality, reduce server load, and improve user experience by speeding up page loading times.

While Flash has been a common option for image resizing, many developers prefer to avoid its use. Fortunately, there is a solution that utilizes JavaScript to resize images effectively.

Open Source Image Resizing Algorithm

The open source algorithm available on GitHub (https://gist.github.com/dcollien/312bce1270a5f511bf4a) provides a reliable method for resizing images client-side. It offers an ES6 version and a .js version that can be included in script tags.

Implementation

To implement the resizing algorithm, follow these steps:

1. Add the HTML code as shown below:

2. Add the JavaScript code below:

document.getElementById('select').onchange = function(evt) {
    ImageTools.resize(this.files[0], {
        width: 320, // maximum width
        height: 240 // maximum height
    }, function(blob, didItResize) {
        // didItResize will be true if it managed to resize it, otherwise false (and will return the original file as 'blob')
        document.getElementById('preview').src = window.URL.createObjectURL(blob);
        // you can also now upload this blob using an XHR.
    });
};

Features and Support

The algorithm boasts a range of features and support, including:

• Resizing based on specified maximum width and height
• Support detection and polyfills for compatibility across browsers
• Exclusion of animated GIFs for efficiency