How to Get the Width and Height of a Base64 Image in JavaScript

Learn how to easily determine the width and height of a Base64 image in JavaScript using an async function and Promises. Perfect for developers looking to enhance their image handling skills!
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This video is based on the question https://stackoverflow.com/q/63969580/ asked by the user 'RAHUL KUNDU' ( https://stackoverflow.com/u/13333147/ ) and on the answer https://stackoverflow.com/a/63969643/ provided by the user 'mousetail' ( https://stackoverflow.com/u/6333444/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Get the Width and Height of a Base64 Image in JavaScript

Are you trying to extract the dimensions of a Base64 image representation but running into problems? You’re not alone! Many developers find themselves stuck when trying to get the width and height of an image from a Base64 string. In this post, we’ll explore how to tackle this issue by creating an efficient helper function in JavaScript.

The Problem

The primary challenge arises when dealing with asynchronous operations in JavaScript. When you load an image, the process does not complete instantly; instead, it loads in the background. In your initial approach, you tried to get the width and height of the image immediately after setting its source. However, since the image hasn’t finished loading yet, you end up with null values for the dimensions.

Here’s a snippet of the code you might have started with:

[[See Video to Reveal this Text or Code Snippet]]

The Solution: Using Async/Await

To effectively get the dimensions of a Base64 image, we need to set up our function to handle the image loading asynchronously. This can be achieved using a Promise. When the image has finished loading, we resolve the Promise with the width and height.

Step-by-Step Implementation

Wrap the Image Loading in a Promise: This will allow us to wait for the image to load before trying to access its dimensions.

Modify the Function to Return a Promise: This change will enable us to use async/await syntax and easily handle the resolved dimensions.

Here’s the revised code that demonstrates this approach:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code:

Async Function: The getDimensions function is modified to return a Promise. This is crucial for handling asynchronous code effectively.

Image Object: A new Image object is created, and its source is set to the provided Base64 image string.

On Load: The onload event handler will be triggered once the image has fully loaded, allowing us to access its dimensions without encountering null values.

Error Handling: An optional onerror handler has been added to manage cases where the image fails to load.

Conclusion

With this method, you can accurately obtain the width and height of a Base64 image in JavaScript. Implementing asynchronous handling with Promises simplifies the image loading process and prevents issues related to accessing dimensions before they are available.

If you're new to Promises and async programming, consider diving into guides on these subjects to deepen your understanding. Happy coding!