mirror of
https://github.com/superseriousbusiness/gotosocial
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96 lines
4 KiB
Markdown
96 lines
4 KiB
Markdown
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# go-blurhash [](https://travis-ci.org/buckket/go-blurhash) [](https://goreportcard.com/report/github.com/buckket/go-blurhash) [](https://codecov.io/gh/buckket/go-blurhash) [](https://pkg.go.dev/github.com/buckket/go-blurhash)
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**go-blurhash** is a pure Go implementation of the [BlurHash](https://github.com/woltapp/blurhash) algorithm, which is used by
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[Mastodon](https://github.com/tootsuite/mastodon) an other Fediverse software to implement a swift way of preloading placeholder images as well
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as hiding sensitive media. Read more about it [here](https://blog.joinmastodon.org/2019/05/improving-support-for-adult-content-on-mastodon/).
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**tl;dr:** BlurHash is a compact representation of a placeholder for an image.
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This library allows generating the BlurHash of a given image, as well as
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reconstructing a blurred version with specified dimensions from a given BlurHash.
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This library is based on the following reference implementations:
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- Encoder: [https://github.com/woltapp/blurhash/blob/master/C](https://github.com/woltapp/blurhash/blob/master/C) (C)
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- Deocder: [https://github.com/woltapp/blurhash/blob/master/TypeScript](https://github.com/woltapp/blurhash/blob/master/TypeScript) (TypeScript)
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BlurHash is written by [Dag Ågren](https://github.com/DagAgren) / [Wolt](https://github.com/woltapp).
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| | Before | After |
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| ---------- |:------------------------------:| :-----------------------------:|
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| **Image** | ![alt text][test] | "LFE.@D9F01_2%L%MIVD*9Goe-;WB" |
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| **Hash** | "LFE.@D9F01_2%L%MIVD*9Goe-;WB" | ![alt text][test_blur]
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[test]: test.png "Blurhash example input."
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[test_blur]: test_blur.png "Blurhash example output"
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## Installation
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### From source
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go get -u github.com/buckket/go-blurhash
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## Usage
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go-blurhash exports three functions:
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```go
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func blurhash.Encode(xComponents, yComponents int, rgba image.Image) (string, error)
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func blurhash.Decode(hash string, width, height, punch int) (image.Image, error)
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func blurhash.Components(hash string) (xComponents, yComponents int, err error)
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```
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Here’s a simple demonstration. Check [pkg.go.dev](https://pkg.go.dev/github.com/buckket/go-blurhash) for the full documentation.
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```go
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package main
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import (
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"fmt"
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"github.com/buckket/go-blurhash"
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"image/png"
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"os"
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)
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func main() {
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// Generate the BlurHash for a given image
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imageFile, _ := os.Open("test.png")
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loadedImage, err := png.Decode(imageFile)
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str, _ := blurhash.Encode(4, 3, loadedImage)
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if err != nil {
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// Handle errors
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}
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fmt.Printf("Hash: %s\n", str)
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// Generate an image for a given BlurHash
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// Width will be 300px and Height will be 500px
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// Punch specifies the contrasts and defaults to 1
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img, err := blurhash.Decode(str, 300, 500, 1)
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if err != nil {
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// Handle errors
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}
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f, _ := os.Create("test_blur.png")
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_ = png.Encode(f, img)
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// Get the x and y components used for encoding a given BlurHash
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x, y, err := blurhash.Components("LFE.@D9F01_2%L%MIVD*9Goe-;WB")
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if err != nil {
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// Handle errors
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}
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fmt.Printf("xComponents: %d, yComponents: %d", x, y)
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}
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```
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## Limitations
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- Presumably a bit slower than the C implementation (TODO: Benchmarks)
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## Notes
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- As mentioned [here](https://github.com/woltapp/blurhash#how-fast-is-encoding-decoding), it’s best to
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generate very small images (~32x32px) via BlurHash and scale them up to the desired dimensions afterwards for optimal performance.
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- Since [#2](https://github.com/buckket/go-blurhash/pull/2) we diverted from the reference implementation by memorizing sRGBtoLinear values, thus increasing encoding speed at the cost of higher memory usage.
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- Starting with v1.1.0 the signature of blurhash.Encode() has changed slightly (see [#3](https://github.com/buckket/go-blurhash/issues/3)).
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## License
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GNU GPLv3+
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