2.2k GitHub stars and counting — mrousavy/react-native-blurhash is a Kotlin project TopGit is tracking across repositories on the platform. 🖼️ A library to show colorful blurry placeholders while your content loads.
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🖼️ Give your users the loading experience they want.
Install via npm:
npm i react-native-blurhash
npx pod-install
BlurHash is a compact representation of a placeholder for an image. Instead of displaying boring grey little boxes while your image loads, show a blurred preview until the full image has been loaded.
The algorithm was created by woltapp/blurhash, which also includes an algorithm explanation.
Expo
✅ You can use this library with Development Builds. No config plugin is required.
❌ This library can't be used in the "Expo Go" app because it requires custom native code.
Example Workflow
In order to use the Blurhash component, you have to already have a Blurhash string. See the blurha.sh page to create example strings.
This is how I use it in my project:
A user creates a post by calling a function on my server which expects a payload of an image and some post data (title, description, ...)
The function on my server then
generates a blurhash from the image in the payload using the C encoder
stores the post data (including the generated blurhash string) in my database
uploads the image to a content delivery network (e.g. AWS)
Now everytime a user loads a feed of posts from my database, I can immediately show a <Blurhash> component (with the post's .blurhash property) over my <Image> component, and fade it out once the <Image> component's onLoadEnd function has been called.
Note: You can also use the react-native-blurhash encoder to encode straight from your React Native App!
Usage
The <Blurhash> component has the following properties:
Name
Type
Explanation
Required
Default Value
blurhash
string
The blurhash string to use. Example: LGFFaXYk^6#M@-5c,1J5@[or[Q6.
✅
undefined
decodeWidth
number
The width (resolution) to decode to. Higher values decrease performance, use 16 for large lists, otherwise you can increase it to 32.
See: performance
❌
32
decodeHeight
number
The height (resolution) to decode to. Higher values decrease performance, use 16 for large lists, otherwise you can increase it to 32.
See: performance
❌
32
decodePunch
number
Adjusts the contrast of the output image. Tweak it if you want a different look for your placeholders.
❌
1.0
decodeAsync
boolean
Asynchronously decode the Blurhash on a background Thread instead of the UI-Thread.
See: Asynchronous Decoding
❌
false
resizeMode
'cover' | 'contain' | 'stretch' | 'center'
Sets the resize mode of the image. (no, 'repeat' is not supported.)
See: Image::resizeMode
❌
'cover'
onLoadStart
() => void
A callback to call when the Blurhash started to decode the given blurhash string.
❌
undefined
onLoadEnd
() => void
A callback to call when the Blurhash successfully decoded the given blurhash string and rendered the image to the <Blurhash> view.
❌
undefined
onLoadError
(message?: string) => void
A callback to call when the Blurhash failed to load. Use the message parameter to get the error message.
❌
undefined
All View props
ViewProps
All properties from the React Native View. Use style.width and style.height for display-sizes. Also, style.borderRadius is natively supported on iOS.
❌
{}
Example Usage:
import { Blurhash } from 'react-native-blurhash';
export default function App() {
return (
<Blurhash
blurhash="LGFFaXYk^6#M@-5c,1J5@[or[Q6."
style={{flex: 1}}
/>
);
}
See the example App for a full code example.
iOS Screenshot
Android Screenshot
Average Color
If your app is really colorful you might want to match some containers' colors to the content's context. To achieve this, use the getAverageColor function to get an RGB value which represents the average color of the given Blurhash:
Because encoding an Image is a pretty heavy task, this function is non-blocking and runs on a separate background Thread.
Validation
If you need to validate a blurhash string, you can use isValidBlurhash.
const result = Blurhash.isValidBlurhash('LGFFaXYk^6#M@-5c,1J5@[or[Q6.')
if (result.isValid) {
console.log(`Blurhash is valid!`)
} else {
console.log(`Blurhash is invalid! ${result.reason}`)
}
Performance
The performance of the decoders is really fast, which means you should be able to use them in collections quite easily. By increasing the decodeWidth and decodeHeight props, the time to decode also increases. I'd recommend values of 16 for large lists, and 32 otherwise. Play around with the values but keep in mind that you probably won't see a difference when increasing it to anything above 32.
Asynchronous Decoding
Use decodeAsync={true} to decode the Blurhash on a separate background Thread instead of the main UI-Thread. This is useful when you are experiencing stutters because of the Blurhash's decoder - e.g.: in large Lists.
Threads are re-used (iOS: DispatchQueue, Android: kotlinx Coroutines).
Caching
Image
A <Blurhash> component caches the rendered Blurhash (Image) as long as the blurhash, decodeWidth, decodeHeight and decodePunch properties stay the same. Because unmounting the <Blurhash> component clears the cache, re-mounting it will cause it to decode again.
Cosine Operations
Cosine operations get cached in memory to avoid expensive re-calculation (~24.576 cos(...) calls per 32x32 blurhash). Since this can affect memory usage, you can manually clear the cosine array cache by calling:
Blurhash.clearCosineCache()
Note: At the moment, cosine operations are only cached on Android. Calling clearCosineCache() is a no-op on other platforms.
Resources
this medium article. jesus christ amen thanks for that
Native Modules documentation, especially the Swift part
This cheatsheet gist thank you @chourobin.
DylanVann/react-native-fast-image as a reference for native UI modules
How active is development on mrousavy/react-native-blurhash?
The most recent commit recorded on mrousavy/react-native-blurhash was 4 months ago, based on the GitHub push timestamp. The repository has 88 forks — one of the better signals of community interest.
How does mrousavy/react-native-blurhash compare to other UI / UX projects?
mrousavy/react-native-blurhash is tracked by TopGit in the UI / UX category, with 2.2k GitHub stars and written in Kotlin. Browse the UI / UX topic page on TopGit to compare it against similar projects by stars and activity.
How many stars does mrousavy/react-native-blurhash have?
mrousavy/react-native-blurhash has 2.2k GitHub stars — refresh the page for the live number, or check github.com/mrousavy/react-native-blurhash. TopGit mirrors GitHub's count but does not claim minute-by-minute accuracy.
Is mrousavy/react-native-blurhash open source?
Yes — mrousavy/react-native-blurhash ships under the MIT license, which makes its source code freely readable (and, depending on license terms, forkable and reusable). Source: github.com/mrousavy/react-native-blurhash.
What is mrousavy/react-native-blurhash?
mrousavy/react-native-blurhash (mrousavy/react-native-blurhash) is a Kotlin project on GitHub. From the project's own README: 🖼️ A library to show colorful blurry placeholders while your content loads.
Where do I read more about mrousavy/react-native-blurhash?
This TopGit page is a snapshot — the READ ME tab shows the project's own README content (links stripped, images preserved). The GitHub repository at github.com/mrousavy/react-native-blurhash is the definitive source.
Read full README in the tab above.
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