Скачать или смотреть How to Reuse Images Efficiently with Canvas in JavaScript

Discover how to avoid repeatedly loading images for the canvas in your JavaScript projects, enhancing performance with memoization techniques.
---
This video is based on the question https://stackoverflow.com/q/63149276/ asked by the user 'Kerrakuu' ( https://stackoverflow.com/u/14004576/ ) and on the answer https://stackoverflow.com/a/63149353/ provided by the user 'sçuçu' ( https://stackoverflow.com/u/2605049/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Reuse an Image with Canvas

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Reuse Images Efficiently with Canvas in JavaScript

When working with HTML5 canvas in web development, one common issue that developers encounter is the repeated loading of images. This not only increases the loading time but also consumes unnecessary resources. If you find your canvas drawing function calling the loadImage method multiple times for the same image, you're not alone. Let's dive into how to resolve this problem efficiently.

The Problem: Repeated Image Loading

In the code snippet below, we see a function called draw that draws images onto a canvas based on tile data. Every time draw is called, it also calls the loadImage function, which loads images from the specified source.

Code Overview

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

This can lead to performance issues because every time the draw function is invoked, the same images are loaded again and again, which is inefficient.

The Solution: Memoizing Image Loading

To avoid the repeated image loading, we can introduce a memoization technique. This means we'll store the loaded images in memory so we can retrieve them without loading the same image multiple times. Here’s how you can implement it.

Step 1: Create an In-Memory Cache

First, we need to modify the loadImage function to include a caching mechanism. We can use a simple object to cache the images based on their source paths.

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

Step 2: Optimize Your Draw Function

Now that we have a caching mechanism in place, we can utilize it in the draw function. Since the images are cached, the loadImage function will resolve with the cached image if it has already been loaded.

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

Additional Considerations

If your tileData is static and never changes, you can call loadImage once during the setup or initialization phase and reuse those images throughout your application.

Monitor your application's memory usage as caching images can increase memory consumption if many large images are stored.

Conclusion

Implementing an in-memory caching solution for images in your canvas drawing code can significantly improve performance by reducing redundant image loading. By memoizing the loadImage function, you ensure that images are only fetched once, allowing your application to run faster and more efficiently.

Start leveraging this technique in your canvas projects today for a smoother user experience!