mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-04 22:20:53 +01:00
96 lines
4.0 KiB
Markdown
96 lines
4.0 KiB
Markdown
|
# 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)
|
|||
|
|
|
|||
|
|
**go-blurhash** is a pure Go implementation of the [BlurHash](https://github.com/woltapp/blurhash) algorithm, which is used by
|
|||
|
|
[Mastodon](https://github.com/tootsuite/mastodon) an other Fediverse software to implement a swift way of preloading placeholder images as well
|
|||
|
|
as hiding sensitive media. Read more about it [here](https://blog.joinmastodon.org/2019/05/improving-support-for-adult-content-on-mastodon/).
|
|||
|
|
|
|||
|
|
**tl;dr:** BlurHash is a compact representation of a placeholder for an image.
|
|||
|
|
|
|||
|
|
This library allows generating the BlurHash of a given image, as well as
|
|||
|
|
reconstructing a blurred version with specified dimensions from a given BlurHash.
|
|||
|
|
|
|||
|
|
This library is based on the following reference implementations:
|
|||
|
|
- Encoder: [https://github.com/woltapp/blurhash/blob/master/C](https://github.com/woltapp/blurhash/blob/master/C) (C)
|
|||
|
|
- Deocder: [https://github.com/woltapp/blurhash/blob/master/TypeScript](https://github.com/woltapp/blurhash/blob/master/TypeScript) (TypeScript)
|
|||
|
|
|
|||
|
|
BlurHash is written by [Dag Ågren](https://github.com/DagAgren) / [Wolt](https://github.com/woltapp).
|
|||
|
|
|
|||
|
|
| | Before | After |
|
|||
|
|
| ---------- |:------------------------------:| :-----------------------------:|
|
|||
|
|
| **Image** | ![alt text][test] | "LFE.@D9F01_2%L%MIVD*9Goe-;WB" |
|
|||
|
|
| **Hash** | "LFE.@D9F01_2%L%MIVD*9Goe-;WB" | ![alt text][test_blur]
|
|||
|
|
|
|||
|
|
[test]: test.png "Blurhash example input."
|
|||
|
|
[test_blur]: test_blur.png "Blurhash example output"
|
|||
|
|
|
|||
|
|
## Installation
|
|||
|
|
|
|||
|
|
### From source
|
|||
|
|
|
|||
|
|
go get -u github.com/buckket/go-blurhash
|
|||
|
|
|
|||
|
|
## Usage
|
|||
|
|
|
|||
|
|
go-blurhash exports three functions:
|
|||
|
|
```go
|
|||
|
|
func blurhash.Encode(xComponents, yComponents int, rgba image.Image) (string, error)
|
|||
|
|
func blurhash.Decode(hash string, width, height, punch int) (image.Image, error)
|
|||
|
|
func blurhash.Components(hash string) (xComponents, yComponents int, err error)
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
Here’s a simple demonstration. Check [pkg.go.dev](https://pkg.go.dev/github.com/buckket/go-blurhash) for the full documentation.
|
|||
|
|
|
|||
|
|
```go
|
|||
|
|
package main
|
|||
|
|
|
|||
|
|
import (
|
|||
|
|
"fmt"
|
|||
|
|
"github.com/buckket/go-blurhash"
|
|||
|
|
"image/png"
|
|||
|
|
"os"
|
|||
|
|
)
|
|||
|
|
|
|||
|
|
func main() {
|
|||
|
|
// Generate the BlurHash for a given image
|
|||
|
|
imageFile, _ := os.Open("test.png")
|
|||
|
|
loadedImage, err := png.Decode(imageFile)
|
|||
|
|
str, _ := blurhash.Encode(4, 3, loadedImage)
|
|||
|
|
if err != nil {
|
|||
|
|
// Handle errors
|
|||
|
|
}
|
|||
|
|
fmt.Printf("Hash: %s\n", str)
|
|||
|
|
|
|||
|
|
// Generate an image for a given BlurHash
|
|||
|
|
// Width will be 300px and Height will be 500px
|
|||
|
|
// Punch specifies the contrasts and defaults to 1
|
|||
|
|
img, err := blurhash.Decode(str, 300, 500, 1)
|
|||
|
|
if err != nil {
|
|||
|
|
// Handle errors
|
|||
|
|
}
|
|||
|
|
f, _ := os.Create("test_blur.png")
|
|||
|
|
_ = png.Encode(f, img)
|
|||
|
|
|
|||
|
|
// Get the x and y components used for encoding a given BlurHash
|
|||
|
|
x, y, err := blurhash.Components("LFE.@D9F01_2%L%MIVD*9Goe-;WB")
|
|||
|
|
if err != nil {
|
|||
|
|
// Handle errors
|
|||
|
|
}
|
|||
|
|
fmt.Printf("xComponents: %d, yComponents: %d", x, y)
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
## Limitations
|
|||
|
|
|
|||
|
|
- Presumably a bit slower than the C implementation (TODO: Benchmarks)
|
|||
|
|
|
|||
|
|
## Notes
|
|||
|
|
|
|||
|
|
- As mentioned [here](https://github.com/woltapp/blurhash#how-fast-is-encoding-decoding), it’s best to
|
|||
|
|
generate very small images (~32x32px) via BlurHash and scale them up to the desired dimensions afterwards for optimal performance.
|
|||
|
|
- 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.
|
|||
|
|
- Starting with v1.1.0 the signature of blurhash.Encode() has changed slightly (see [#3](https://github.com/buckket/go-blurhash/issues/3)).
|
|||
|
|
|
|||
|
|
## License
|
|||
|
|
|
|||
|
|
GNU GPLv3+
|
|||
|
|
|