├── .github └── FUNDING.yml ├── .gitignore ├── .travis.yml ├── LICENSE ├── README.md ├── base83 ├── base83.go └── base83_test.go ├── decode.go ├── decode_test.go ├── encode.go ├── encode_test.go ├── go.mod ├── test.png ├── test_blur.png ├── utils.go └── utils_test.go /.github/FUNDING.yml: -------------------------------------------------------------------------------- 1 | # These are supported funding model platforms 2 | 3 | github: # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2] 4 | patreon: # Replace with a single Patreon username 5 | open_collective: # Replace with a single Open Collective username 6 | ko_fi: # Replace with a single Ko-fi username 7 | tidelift: # Replace with a single Tidelift platform-name/package-name e.g., npm/babel 8 | community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry 9 | liberapay: buckket # Replace with a single Liberapay username 10 | issuehunt: # Replace with a single IssueHunt username 11 | otechie: # Replace with a single Otechie username 12 | custom: # Replace with up to 4 custom sponsorship URLs e.g., ['link1', 'link2'] 13 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | .idea 2 | coverage.txt -------------------------------------------------------------------------------- /.travis.yml: -------------------------------------------------------------------------------- 1 | language: go 2 | 3 | go: 4 | - 1.15.x 5 | - 1.14.x 6 | 7 | install: 8 | - go get -t -v ./... 9 | 10 | script: 11 | - go test -race -coverprofile=coverage.txt -covermode=atomic ./... 12 | 13 | after_success: 14 | - bash <(curl -s https://codecov.io/bash) 15 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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Limitation of Liability. 601 | 602 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 603 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 604 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 605 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 606 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 607 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 608 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 609 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 610 | SUCH DAMAGES. 611 | 612 | 17. Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # go-blurhash [![Build Status](https://travis-ci.org/buckket/go-blurhash.svg)](https://travis-ci.org/buckket/go-blurhash) [![Go Report Card](https://goreportcard.com/badge/github.com/buckket/go-blurhash)](https://goreportcard.com/report/github.com/buckket/go-blurhash) [![codecov](https://codecov.io/gh/buckket/go-blurhash/branch/master/graph/badge.svg)](https://codecov.io/gh/buckket/go-blurhash) [![GoDoc](https://godoc.org/github.com/buckket/go-blurhash?status.svg)](https://pkg.go.dev/github.com/buckket/go-blurhash) 2 | 3 | **go-blurhash** is a pure Go implementation of the [BlurHash](https://github.com/woltapp/blurhash) algorithm, which is used by 4 | [Mastodon](https://github.com/tootsuite/mastodon) an other Fediverse software to implement a swift way of preloading placeholder images as well 5 | as hiding sensitive media. Read more about it [here](https://blog.joinmastodon.org/2019/05/improving-support-for-adult-content-on-mastodon/). 6 | 7 | **tl;dr:** BlurHash is a compact representation of a placeholder for an image. 8 | 9 | This library allows generating the BlurHash of a given image, as well as 10 | reconstructing a blurred version with specified dimensions from a given BlurHash. 11 | 12 | This library is based on the following reference implementations: 13 | - Encoder: [https://github.com/woltapp/blurhash/blob/master/C](https://github.com/woltapp/blurhash/blob/master/C) (C) 14 | - Decoder: [https://github.com/woltapp/blurhash/blob/master/TypeScript](https://github.com/woltapp/blurhash/blob/master/TypeScript) (TypeScript) 15 | 16 | BlurHash is written by [Dag Ågren](https://github.com/DagAgren) / [Wolt](https://github.com/woltapp). 17 | 18 | | | Before | After | 19 | | ---------- |:------------------------------:| :-----------------------------:| 20 | | **Image** | ![alt text][test] | "LFE.@D9F01_2%L%MIVD*9Goe-;WB" | 21 | | **Hash** | "LFE.@D9F01_2%L%MIVD*9Goe-;WB" | ![alt text][test_blur] 22 | 23 | [test]: test.png "Blurhash example input." 24 | [test_blur]: test_blur.png "Blurhash example output" 25 | 26 | ## Installation 27 | 28 | ### From source 29 | 30 | go get -u github.com/buckket/go-blurhash 31 | 32 | ## Usage 33 | 34 | go-blurhash exports three functions: 35 | ```go 36 | func blurhash.Encode(xComponents, yComponents int, rgba image.Image) (string, error) 37 | func blurhash.Decode(hash string, width, height, punch int) (image.Image, error) 38 | func blurhash.Components(hash string) (xComponents, yComponents int, err error) 39 | ``` 40 | 41 | Here’s a simple demonstration. Check [pkg.go.dev](https://pkg.go.dev/github.com/buckket/go-blurhash) for the full documentation. 42 | 43 | ```go 44 | package main 45 | 46 | import ( 47 | "fmt" 48 | "github.com/buckket/go-blurhash" 49 | "image/png" 50 | "os" 51 | ) 52 | 53 | func main() { 54 | // Generate the BlurHash for a given image 55 | imageFile, _ := os.Open("test.png") 56 | loadedImage, err := png.Decode(imageFile) 57 | str, _ := blurhash.Encode(4, 3, loadedImage) 58 | if err != nil { 59 | // Handle errors 60 | } 61 | fmt.Printf("Hash: %s\n", str) 62 | 63 | // Generate an image for a given BlurHash 64 | // Width will be 300px and Height will be 500px 65 | // Punch specifies the contrasts and defaults to 1 66 | img, err := blurhash.Decode(str, 300, 500, 1) 67 | if err != nil { 68 | // Handle errors 69 | } 70 | f, _ := os.Create("test_blur.png") 71 | _ = png.Encode(f, img) 72 | 73 | // Get the x and y components used for encoding a given BlurHash 74 | x, y, err := blurhash.Components("LFE.@D9F01_2%L%MIVD*9Goe-;WB") 75 | if err != nil { 76 | // Handle errors 77 | } 78 | fmt.Printf("xComponents: %d, yComponents: %d", x, y) 79 | } 80 | ``` 81 | 82 | ## Limitations 83 | 84 | - Presumably a bit slower than the C implementation (TODO: Benchmarks) 85 | 86 | ## Notes 87 | 88 | - As mentioned [here](https://github.com/woltapp/blurhash#how-fast-is-encoding-decoding), it’s best to 89 | generate very small images (~32x32px) via BlurHash and scale them up to the desired dimensions afterwards for optimal performance. 90 | - 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. 91 | - Starting with v1.1.0 the signature of blurhash.Encode() has changed slightly (see [#3](https://github.com/buckket/go-blurhash/issues/3)). 92 | 93 | ## License 94 | 95 | GNU GPLv3+ 96 | 97 | -------------------------------------------------------------------------------- /base83/base83.go: -------------------------------------------------------------------------------- 1 | package base83 2 | 3 | import ( 4 | "fmt" 5 | "math" 6 | "strings" 7 | ) 8 | 9 | const characters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz#$%*+,-.:;=?@[]^_{|}~" 10 | 11 | // An InvalidCharacterError occurs when a characters is found which is not part of the Base83 character set. 12 | type InvalidCharacterError rune 13 | 14 | func (e InvalidCharacterError) Error() string { 15 | return fmt.Sprintf("base83: invalid string (character %q out of range)", rune(e)) 16 | } 17 | 18 | // An InvalidLengthError occurs when a given value cannot be encoded to a string of given length. 19 | type InvalidLengthError int 20 | 21 | func (e InvalidLengthError) Error() string { 22 | return fmt.Sprintf("base83: invalid length (%d)", int(e)) 23 | } 24 | 25 | // Encode will encode the given integer value to a Base83 string with given length. 26 | // If length is too short to encode the given value InvalidLengthError will be returned. 27 | func Encode(value, length int) (string, error) { 28 | divisor := int(math.Pow(83, float64(length))) 29 | if value/divisor != 0 { 30 | return "", InvalidLengthError(length) 31 | } 32 | divisor /= 83 33 | 34 | var str strings.Builder 35 | str.Grow(length) 36 | for i := 0; i < length; i++ { 37 | if divisor <= 0 { 38 | return "", InvalidLengthError(length) 39 | } 40 | digit := (value / divisor) % 83 41 | divisor /= 83 42 | str.WriteRune(rune(characters[digit])) 43 | } 44 | 45 | return str.String(), nil 46 | } 47 | 48 | // Decode will decode the given Base83 string to an integer. 49 | func Decode(str string) (value int, err error) { 50 | for _, r := range str { 51 | idx := strings.IndexRune(characters, r) 52 | if idx == -1 { 53 | return 0, InvalidCharacterError(r) 54 | } 55 | value = value*83 + idx 56 | } 57 | return value, nil 58 | } 59 | -------------------------------------------------------------------------------- /base83/base83_test.go: -------------------------------------------------------------------------------- 1 | package base83_test 2 | 3 | import ( 4 | "fmt" 5 | "github.com/buckket/go-blurhash/base83" 6 | "testing" 7 | ) 8 | 9 | func TestDecode(t *testing.T) { 10 | var testCasesValid = []struct { 11 | in string 12 | out int 13 | }{ 14 | {"", 0}, 15 | {"foobar", 163902429697}, 16 | {"LFE.@D9F01_2%L%MIVD*9Goe-;WB", -1597651267176502418}, 17 | } 18 | 19 | for _, tc := range testCasesValid { 20 | t.Run(fmt.Sprintf("%q", tc.in), func(t *testing.T) { 21 | out, err := base83.Decode(tc.in) 22 | if err != nil { 23 | t.Fatal(err) 24 | } 25 | if out != tc.out { 26 | t.Fatalf("got %d, wanted %d", out, tc.out) 27 | } 28 | }) 29 | } 30 | 31 | _, err := base83.Decode("LFE.@D9F01_2%L%MIVD*9Goe-;Wµ") 32 | if err == nil { 33 | t.Fatal("should have failed") 34 | } 35 | 36 | err, ok := err.(base83.InvalidCharacterError) 37 | if !ok { 38 | t.Fatal("wrong error type") 39 | } 40 | _ = err.Error() 41 | } 42 | 43 | func BenchmarkDecode(b *testing.B) { 44 | for i := 0; i < b.N; i++ { 45 | _, _ = base83.Decode("~$") 46 | } 47 | } 48 | 49 | func TestEncode(t *testing.T) { 50 | var testCasesValid = []struct { 51 | in int 52 | length int 53 | out string 54 | }{ 55 | {0, 0, ""}, 56 | {163902429697, 6, "foobar"}, 57 | {100, 2, "1H"}, 58 | } 59 | 60 | for _, tc := range testCasesValid { 61 | t.Run(fmt.Sprintf("%d", tc.in), func(t *testing.T) { 62 | out, err := base83.Encode(tc.in, tc.length) 63 | if err != nil { 64 | t.Fatal(err) 65 | } 66 | if out != tc.out { 67 | t.Fatalf("got %q, wanted %q", out, tc.out) 68 | } 69 | }) 70 | } 71 | 72 | var testCasesInvalid = []struct { 73 | in int 74 | length int 75 | }{ 76 | {84, 1}, 77 | {-1597651267176502418, 16}, 78 | {163902429697, 10}, 79 | } 80 | 81 | for _, tc := range testCasesInvalid { 82 | t.Run(fmt.Sprintf("%d", tc.in), func(t *testing.T) { 83 | _, err := base83.Encode(tc.in, tc.length) 84 | if err == nil { 85 | t.Fatal("should have failed") 86 | } 87 | 88 | err, ok := err.(base83.InvalidLengthError) 89 | if !ok { 90 | t.Fatal("wrong error type") 91 | } 92 | _ = err.Error() 93 | }) 94 | } 95 | } 96 | 97 | func BenchmarkEncode(b *testing.B) { 98 | for i := 0; i < b.N; i++ { 99 | _, _ = base83.Encode(6869, 2) 100 | } 101 | } 102 | -------------------------------------------------------------------------------- /decode.go: -------------------------------------------------------------------------------- 1 | package blurhash 2 | 3 | import ( 4 | "fmt" 5 | "github.com/buckket/go-blurhash/base83" 6 | "image" 7 | "image/color" 8 | "math" 9 | ) 10 | 11 | // An InvalidHashError occurs when the given hash is either too short or the length does not match its size flag. 12 | type InvalidHashError string 13 | 14 | func (e InvalidHashError) Error() string { 15 | return fmt.Sprintf("blurhash: %s", string(e)) 16 | } 17 | 18 | // Components decodes and returns the number of x and y components in the given BlurHash. 19 | func Components(hash string) (xComponents, yComponents int, err error) { 20 | if len(hash) < 6 { 21 | return 0, 0, InvalidHashError("hash is invalid (too short)") 22 | } 23 | 24 | sizeFlag, err := base83.Decode(string(hash[0])) 25 | if err != nil { 26 | return 0, 0, err 27 | } 28 | 29 | yComponents = (sizeFlag / 9) + 1 30 | xComponents = (sizeFlag % 9) + 1 31 | 32 | if len(hash) != 4+2*xComponents*yComponents { 33 | return 0, 0, InvalidHashError("hash is invalid (length mismatch)") 34 | } 35 | 36 | return xComponents, yComponents, nil 37 | } 38 | 39 | // Decode generates an image of the given BlurHash with a size of width and height. 40 | // Punch is a multiplier that adjusts the contrast of the resulting image. 41 | func Decode(hash string, width, height, punch int) (image.Image, error) { 42 | xComp, yComp, err := Components(hash) 43 | if err != nil { 44 | return nil, err 45 | } 46 | 47 | quantisedMaximumValue, err := base83.Decode(string(hash[1])) 48 | if err != nil { 49 | return nil, err 50 | } 51 | maximumValue := (float64(quantisedMaximumValue) + 1) / 166 52 | 53 | if punch == 0 { 54 | punch = 1 55 | } 56 | 57 | colors := make([][3]float64, xComp*yComp) 58 | 59 | for i := range colors { 60 | if i == 0 { 61 | value, err := base83.Decode(hash[2:6]) 62 | if err != nil { 63 | return nil, err 64 | } 65 | colors[i] = decodeDC(value) 66 | } else { 67 | value, err := base83.Decode(hash[4+i*2 : 6+i*2]) 68 | if err != nil { 69 | return nil, err 70 | } 71 | colors[i] = decodeAC(value, maximumValue*float64(punch)) 72 | } 73 | } 74 | 75 | img := image.NewNRGBA(image.Rect(0, 0, width, height)) 76 | 77 | for y := 0; y < height; y++ { 78 | for x := 0; x < width; x++ { 79 | var r, g, b float64 80 | for j := 0; j < yComp; j++ { 81 | for i := 0; i < xComp; i++ { 82 | basis := math.Cos(math.Pi*float64(x)*float64(i)/float64(width)) * 83 | math.Cos(math.Pi*float64(y)*float64(j)/float64(height)) 84 | pcolor := colors[i+j*xComp] 85 | r += pcolor[0] * basis 86 | g += pcolor[1] * basis 87 | b += pcolor[2] * basis 88 | } 89 | } 90 | img.SetNRGBA(x, y, color.NRGBA{R: uint8(linearTosRGB(r)), G: uint8(linearTosRGB(g)), B: uint8(linearTosRGB(b)), A: 255}) 91 | } 92 | } 93 | 94 | return img, nil 95 | } 96 | 97 | func decodeDC(value int) [3]float64 { 98 | return [3]float64{sRGBToLinear(value >> 16), sRGBToLinear(value >> 8 & 255), sRGBToLinear(value & 255)} 99 | } 100 | 101 | func decodeAC(value int, maximumValue float64) [3]float64 { 102 | quantR := math.Floor(float64(value) / (19 * 19)) 103 | quantG := math.Mod(math.Floor(float64(value)/19), 19) 104 | quantB := math.Mod(float64(value), 19) 105 | sp := func(quant float64) float64 { 106 | return signPow((quant-9)/9, 2.0) * maximumValue 107 | } 108 | return [3]float64{sp(quantR), sp(quantG), sp(quantB)} 109 | } 110 | -------------------------------------------------------------------------------- /decode_test.go: -------------------------------------------------------------------------------- 1 | package blurhash_test 2 | 3 | import ( 4 | "fmt" 5 | "github.com/buckket/go-blurhash" 6 | "image/color" 7 | "image/png" 8 | "os" 9 | "testing" 10 | ) 11 | 12 | func TestComponents(t *testing.T) { 13 | const str = "LFE.@D9F01_2%L%MIVD*9Goe-;WB" 14 | 15 | x, y, err := blurhash.Components(str) 16 | if err != nil { 17 | t.Fatal(err) 18 | } 19 | if x != 4 || y != 3 { 20 | t.Fatalf("component missmatch") 21 | } 22 | 23 | _, _, err = blurhash.Components("12345") 24 | if err == nil { 25 | t.Fatal("should have failed") 26 | } 27 | err, ok := err.(blurhash.InvalidHashError) 28 | if !ok { 29 | t.Fatal("wrong error type") 30 | } 31 | _ = err.Error() 32 | 33 | _, _, err = blurhash.Components(str[:9]) 34 | if err == nil { 35 | t.Fatal("should have failed") 36 | } 37 | err, ok = err.(blurhash.InvalidHashError) 38 | if !ok { 39 | t.Fatal("wrong error type") 40 | } 41 | _ = err.Error() 42 | } 43 | 44 | func TestDecodeFile(t *testing.T) { 45 | const str = "LFE.@D9F01_2%L%MIVD*9Goe-;WB" 46 | 47 | imageFile, err := os.Open("test_blur.png") 48 | if err != nil { 49 | t.Fatal("could not load test_blur.png") 50 | } 51 | 52 | loadedImage, err := png.Decode(imageFile) 53 | if err != nil { 54 | t.Fatal("could not decode test_blur.png") 55 | } 56 | 57 | img, err := blurhash.Decode(str, 204, 204, 1) 58 | if err != nil { 59 | t.Fatal(err) 60 | } 61 | 62 | if loadedImage.Bounds() != img.Bounds() { 63 | t.Fatal("bounds mismatch") 64 | } 65 | 66 | width, height := img.Bounds().Max.X, img.Bounds().Max.Y 67 | for x := 0; x < width; x++ { 68 | for y := 0; y < height; y++ { 69 | r1, g1, b1, a1 := img.At(x, y).RGBA() 70 | r2, g2, b2, a2 := loadedImage.At(x, y).RGBA() 71 | if r1 != r2 || g1 != g2 || b1 != b2 || a1 != a2 { 72 | t.Fatalf("pixel mismatch") 73 | } 74 | } 75 | } 76 | 77 | } 78 | 79 | func TestDecodeSingleColor(t *testing.T) { 80 | const str = "00OZZy" 81 | 82 | img, err := blurhash.Decode(str, 1, 1, 0) 83 | if err != nil { 84 | t.Fatal(err) 85 | } 86 | 87 | r, g, b, a := img.At(0, 0).RGBA() 88 | bcolor := color.RGBA{uint8(r), uint8(g), uint8(b), uint8(a)} 89 | tcolor := color.RGBA{213, 30, 120, 255} 90 | if bcolor != tcolor { 91 | t.Fatal("color mismatch") 92 | } 93 | } 94 | 95 | func TestDecodeInvalidInput(t *testing.T) { 96 | testCases := []string{ 97 | "00OZZy1", 98 | "\x000OZZy", 99 | "0\x00OZZy", 100 | "00\x00ZZy", 101 | "00O\x00Zy", 102 | "00OZ\x00y", 103 | "00OZZ\x00", 104 | "LFE.@D\x00F01_2%L%MIVD*9Goe-;WB", 105 | } 106 | 107 | for _, tc := range testCases { 108 | t.Run(fmt.Sprintf("str: %s", tc), func(t *testing.T) { 109 | _, err := blurhash.Decode(tc, 32, 32, 1) 110 | if err == nil { 111 | t.Fatal("should have failed") 112 | } 113 | }) 114 | } 115 | } 116 | 117 | func BenchmarkDecode(b *testing.B) { 118 | const str = "LFE.@D9F01_2%L%MIVD*9Goe-;WB" 119 | 120 | for i := 0; i < b.N; i++ { 121 | _, _ = blurhash.Decode(str, 32, 32, 1) 122 | } 123 | } 124 | 125 | func BenchmarkComponents(b *testing.B) { 126 | const str = "LFE.@D9F01_2%L%MIVD*9Goe-;WB" 127 | 128 | for i := 0; i < b.N; i++ { 129 | _, _, _ = blurhash.Components(str) 130 | } 131 | } 132 | 133 | func ExampleDecode() { 134 | img, err := blurhash.Decode("LFE.@D9F01_2%L%MIVD*9Goe-;WB", 204, 204, 1) 135 | if err != nil { 136 | // Handling errors 137 | } 138 | f, _ := os.Create("test_blur.png") 139 | _ = png.Encode(f, img) 140 | } 141 | 142 | func ExampleComponents() { 143 | x, y, err := blurhash.Components("LFE.@D9F01_2%L%MIVD*9Goe-;WB") 144 | if err != nil { 145 | // Handle errors 146 | } 147 | fmt.Printf("xComponents: %d, yComponents: %d", x, y) 148 | // Output: 149 | // xComponents: 4, yComponents: 3 150 | } 151 | -------------------------------------------------------------------------------- /encode.go: -------------------------------------------------------------------------------- 1 | package blurhash 2 | 3 | import ( 4 | "fmt" 5 | "github.com/buckket/go-blurhash/base83" 6 | "image" 7 | "math" 8 | "strings" 9 | ) 10 | 11 | func init() { 12 | initLinearTable(channelToLinear[:]) 13 | } 14 | 15 | var channelToLinear [256]float64 16 | 17 | func initLinearTable(table []float64) { 18 | for i := range table { 19 | channelToLinear[i] = sRGBToLinear(i) 20 | } 21 | } 22 | 23 | // An InvalidParameterError occurs when an invalid argument is passed to either the Decode or Encode function. 24 | type InvalidParameterError struct { 25 | Value int 26 | Parameter string 27 | } 28 | 29 | func (e InvalidParameterError) Error() string { 30 | return fmt.Sprintf("blurhash: %sComponents (%d) must be element of [1-9]", e.Parameter, e.Value) 31 | } 32 | 33 | // An EncodingError represents an error that occurred during the encoding of the given value. 34 | // This most likely means that your input image is invalid and can not be processed. 35 | type EncodingError string 36 | 37 | func (e EncodingError) Error() string { 38 | return fmt.Sprintf("blurhash: %s", string(e)) 39 | } 40 | 41 | // Encode calculates the Blurhash for an image using the given x and y component counts. 42 | // The x and y components have to be between 1 and 9 respectively. 43 | // The image must be of image.Image type. 44 | func Encode(xComponents int, yComponents int, rgba image.Image) (string, error) { 45 | if xComponents < 1 || xComponents > 9 { 46 | return "", InvalidParameterError{xComponents, "x"} 47 | } 48 | if yComponents < 1 || yComponents > 9 { 49 | return "", InvalidParameterError{yComponents, "y"} 50 | } 51 | 52 | var blurhash strings.Builder 53 | blurhash.Grow(4 + 2*xComponents*yComponents) 54 | 55 | // Size Flag 56 | str, err := base83.Encode((xComponents-1)+(yComponents-1)*9, 1) 57 | if err != nil { 58 | return "", EncodingError("could not encode size flag") 59 | } 60 | blurhash.WriteString(str) 61 | 62 | factors := make([]float64, yComponents*xComponents*3) 63 | multiplyBasisFunction(rgba, factors, xComponents, yComponents) 64 | 65 | var maximumValue float64 66 | var quantisedMaximumValue int 67 | var acCount = xComponents*yComponents - 1 68 | if acCount > 0 { 69 | var actualMaximumValue float64 70 | for i := 0; i < acCount*3; i++ { 71 | actualMaximumValue = math.Max(math.Abs(factors[i+3]), actualMaximumValue) 72 | } 73 | quantisedMaximumValue = int(math.Max(0, math.Min(82, math.Floor(actualMaximumValue*166-0.5)))) 74 | maximumValue = (float64(quantisedMaximumValue) + 1) / 166 75 | } else { 76 | maximumValue = 1 77 | } 78 | 79 | // Quantised max AC component 80 | str, err = base83.Encode(quantisedMaximumValue, 1) 81 | if err != nil { 82 | return "", EncodingError("could not encode quantised max AC component") 83 | } 84 | blurhash.WriteString(str) 85 | 86 | // DC value 87 | str, err = base83.Encode(encodeDC(factors[0], factors[1], factors[2]), 4) 88 | if err != nil { 89 | return "", EncodingError("could not encode DC value") 90 | } 91 | blurhash.WriteString(str) 92 | 93 | // AC values 94 | for i := 0; i < acCount; i++ { 95 | str, err = base83.Encode(encodeAC(factors[3+(i*3+0)], factors[3+(i*3+1)], factors[3+(i*3+2)], maximumValue), 2) 96 | if err != nil { 97 | return "", EncodingError("could not encode AC value") 98 | } 99 | blurhash.WriteString(str) 100 | } 101 | 102 | if blurhash.Len() != 4+2*xComponents*yComponents { 103 | return "", EncodingError("hash does not match expected size") 104 | } 105 | 106 | return blurhash.String(), nil 107 | } 108 | 109 | func multiplyBasisFunction(rgba image.Image, factors []float64, xComponents int, yComponents int) { 110 | height := rgba.Bounds().Max.Y 111 | width := rgba.Bounds().Max.X 112 | 113 | xvalues := make([][]float64, xComponents) 114 | for xComponent := 0; xComponent < xComponents; xComponent++ { 115 | xvalues[xComponent] = make([]float64, width) 116 | for x := 0; x < width; x++ { 117 | xvalues[xComponent][x] = math.Cos(math.Pi * float64(xComponent) * float64(x) / float64(width)) 118 | } 119 | } 120 | 121 | yvalues := make([][]float64, yComponents) 122 | for yComponent := 0; yComponent < yComponents; yComponent++ { 123 | yvalues[yComponent] = make([]float64, height) 124 | for y := 0; y < height; y++ { 125 | yvalues[yComponent][y] = math.Cos(math.Pi * float64(yComponent) * float64(y) / float64(height)) 126 | } 127 | } 128 | 129 | for y := 0; y < height; y++ { 130 | for x := 0; x < width; x++ { 131 | rt, gt, bt, _ := rgba.At(x, y).RGBA() 132 | lr := channelToLinear[rt>>8] 133 | lg := channelToLinear[gt>>8] 134 | lb := channelToLinear[bt>>8] 135 | 136 | for yc := 0; yc < yComponents; yc++ { 137 | for xc := 0; xc < xComponents; xc++ { 138 | 139 | scale := 1 / float64(width*height) 140 | 141 | if xc != 0 || yc != 0 { 142 | scale = 2 / float64(width*height) 143 | } 144 | 145 | basis := xvalues[xc][x] * yvalues[yc][y] 146 | factors[0+xc*3+yc*3*xComponents] += lr * basis * scale 147 | factors[1+xc*3+yc*3*xComponents] += lg * basis * scale 148 | factors[2+xc*3+yc*3*xComponents] += lb * basis * scale 149 | } 150 | } 151 | } 152 | } 153 | } 154 | 155 | func encodeDC(r, g, b float64) int { 156 | return (linearTosRGB(r) << 16) + (linearTosRGB(g) << 8) + linearTosRGB(b) 157 | } 158 | 159 | func encodeAC(r, g, b, maximumValue float64) int { 160 | quant := func(f float64) int { 161 | return int(math.Max(0, math.Min(18, math.Floor(signPow(f/maximumValue, 0.5)*9+9.5)))) 162 | } 163 | return quant(r)*19*19 + quant(g)*19 + quant(b) 164 | } 165 | -------------------------------------------------------------------------------- /encode_test.go: -------------------------------------------------------------------------------- 1 | package blurhash_test 2 | 3 | import ( 4 | "fmt" 5 | "github.com/buckket/go-blurhash" 6 | "image" 7 | "image/color" 8 | "image/draw" 9 | "image/png" 10 | "os" 11 | "testing" 12 | ) 13 | 14 | func TestEncodeFile(t *testing.T) { 15 | imageFile, err := os.Open("test.png") 16 | if err != nil { 17 | t.Fatal("could not load test.png") 18 | } 19 | 20 | loadedImage, err := png.Decode(imageFile) 21 | if err != nil { 22 | t.Fatal("could not decode test.png") 23 | } 24 | 25 | str, err := blurhash.Encode(4, 3, loadedImage) 26 | if err != nil { 27 | t.Fatal(err) 28 | return 29 | } 30 | 31 | const expectedHash = "LFE.@D9F01_2%L%MIVD*9Goe-;WB" 32 | if str != expectedHash { 33 | t.Fatalf("got %q, expected %q", str, expectedHash) 34 | } 35 | } 36 | 37 | func TestEncodeWrongParameters(t *testing.T) { 38 | testCases := []struct { 39 | xComp int 40 | yComp int 41 | }{ 42 | {0, 1}, 43 | {1, 0}, 44 | {0, 0}, 45 | {10, 1}, 46 | {1, 10}, 47 | {10, 10}, 48 | {-1, -1}, 49 | } 50 | 51 | var img image.Image 52 | img = image.NewNRGBA(image.Rect(0, 0, 100, 100)) 53 | 54 | for _, tc := range testCases { 55 | t.Run(fmt.Sprintf("xComp:%d yComp:%d", tc.xComp, tc.yComp), func(t *testing.T) { 56 | _, err := blurhash.Encode(tc.xComp, tc.yComp, img) 57 | if err == nil { 58 | t.Fatal("should have failed") 59 | } 60 | err, ok := err.(blurhash.InvalidParameterError) 61 | if !ok { 62 | t.Fatal("wrong error type") 63 | } 64 | _ = err.Error() 65 | }) 66 | } 67 | } 68 | 69 | func TestEncodeEmptyImage(t *testing.T) { 70 | var img image.Image 71 | img = image.NewNRGBA(image.Rect(0, 0, 100, 100)) 72 | 73 | str, err := blurhash.Encode(4, 3, img) 74 | if err != nil { 75 | t.Fatal(err) 76 | } 77 | const expectedHash = "L00000fQfQfQfQfQfQfQfQfQfQfQ" 78 | if str != expectedHash { 79 | t.Fatalf("got %q, expected %q", str, expectedHash) 80 | } 81 | } 82 | 83 | func TestEncodeSizeFlag(t *testing.T) { 84 | testCases := []struct { 85 | xComp int 86 | yComp int 87 | }{ 88 | {1, 2}, 89 | {9, 8}, 90 | {5, 4}, 91 | {2, 3}, 92 | {4, 5}, 93 | {7, 3}, 94 | } 95 | 96 | var img image.Image 97 | img = image.NewNRGBA(image.Rect(0, 0, 100, 100)) 98 | 99 | for _, tc := range testCases { 100 | t.Run(fmt.Sprintf("xComp:%d yComp:%d", tc.xComp, tc.yComp), func(t *testing.T) { 101 | str, err := blurhash.Encode(tc.xComp, tc.yComp, img) 102 | if err != nil { 103 | t.Fatal(err) 104 | } 105 | xComp, yComp, err := blurhash.Components(str) 106 | if err != nil { 107 | t.Fatal(err) 108 | } 109 | if xComp != tc.xComp || yComp != tc.yComp { 110 | t.Fatal("component mismatch") 111 | } 112 | }) 113 | } 114 | } 115 | 116 | func TestEncodeSingleColor(t *testing.T) { 117 | img := image.NewNRGBA(image.Rect(0, 0, 100, 100)) 118 | tcolor := color.RGBA{213, 30, 120, 255} 119 | draw.Draw(img, img.Bounds(), &image.Uniform{tcolor}, image.ZP, draw.Src) 120 | var img2 image.Image = img 121 | 122 | str, err := blurhash.Encode(1, 1, img2) 123 | if err != nil { 124 | t.Fatal(err) 125 | } 126 | const expectedHash = "00OZZy" 127 | if str != expectedHash { 128 | t.Fatalf("got %q, expected %q", str, expectedHash) 129 | } 130 | } 131 | 132 | func BenchmarkEncode(b *testing.B) { 133 | imageFile, err := os.Open("test.png") 134 | if err != nil { 135 | b.Fatal("could not load test.png") 136 | } 137 | 138 | loadedImage, err := png.Decode(imageFile) 139 | if err != nil { 140 | b.Fatal("could not decode test.png") 141 | } 142 | 143 | for i := 0; i < b.N; i++ { 144 | _, _ = blurhash.Encode(4, 3, loadedImage) 145 | } 146 | } 147 | 148 | func ExampleEncode() { 149 | imageFile, _ := os.Open("test.png") 150 | loadedImage, _ := png.Decode(imageFile) 151 | str, err := blurhash.Encode(4, 3, loadedImage) 152 | if err != nil { 153 | // Handle errors 154 | } 155 | fmt.Printf("Hash: %s", str) 156 | // Output: 157 | // Hash: LFE.@D9F01_2%L%MIVD*9Goe-;WB 158 | } 159 | -------------------------------------------------------------------------------- /go.mod: -------------------------------------------------------------------------------- 1 | module github.com/buckket/go-blurhash 2 | 3 | go 1.15 4 | -------------------------------------------------------------------------------- /test.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/buckket/go-blurhash/b97bf3be66e810606e1d08a69abe46608772b05e/test.png -------------------------------------------------------------------------------- /test_blur.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/buckket/go-blurhash/b97bf3be66e810606e1d08a69abe46608772b05e/test_blur.png -------------------------------------------------------------------------------- /utils.go: -------------------------------------------------------------------------------- 1 | package blurhash 2 | 3 | import "math" 4 | 5 | func linearTosRGB(value float64) int { 6 | v := math.Max(0, math.Min(1, value)) 7 | if v <= 0.0031308 { 8 | return int(v*12.92*255 + 0.5) 9 | } 10 | return int((1.055*math.Pow(v, 1/2.4)-0.055)*255 + 0.5) 11 | } 12 | 13 | func sRGBToLinear(value int) float64 { 14 | v := float64(value) / 255 15 | if v <= 0.04045 { 16 | return v / 12.92 17 | } 18 | return math.Pow((v+0.055)/1.055, 2.4) 19 | } 20 | 21 | func signPow(value, exp float64) float64 { 22 | return math.Copysign(math.Pow(math.Abs(value), exp), value) 23 | } 24 | -------------------------------------------------------------------------------- /utils_test.go: -------------------------------------------------------------------------------- 1 | package blurhash 2 | 3 | import ( 4 | "fmt" 5 | "math" 6 | "testing" 7 | ) 8 | 9 | func TestSignPow(t *testing.T) { 10 | var testCases = []struct { 11 | in float64 12 | exp float64 13 | out float64 14 | }{ 15 | {-2.0, 4, -16.0}, 16 | {2.0, 4, 16.0}, 17 | } 18 | 19 | for _, tc := range testCases { 20 | t.Run(fmt.Sprintf("%f", tc.in), func(t *testing.T) { 21 | sp := signPow(tc.in, tc.exp) 22 | if sp != tc.out { 23 | t.Fatalf("got %f, wanted %f", sp, tc.out) 24 | } 25 | }) 26 | } 27 | } 28 | 29 | func TestLinearTosRGB(t *testing.T) { 30 | var testCases = []struct { 31 | in float64 32 | out int 33 | }{ 34 | {0.0, 0}, 35 | {1.0, 255}, 36 | {0.5, 188}, 37 | } 38 | 39 | for _, tc := range testCases { 40 | t.Run(fmt.Sprintf("%f", tc.in), func(t *testing.T) { 41 | sp := linearTosRGB(tc.in) 42 | if sp != tc.out { 43 | t.Fatalf("got %d, wanted %d", sp, tc.out) 44 | } 45 | }) 46 | } 47 | } 48 | 49 | func TestSRGBToLinear(t *testing.T) { 50 | var testCases = []struct { 51 | in int 52 | out float64 53 | }{ 54 | {0, 0.0}, 55 | {255, 1.0}, 56 | {188, 0.5}, 57 | } 58 | 59 | for _, tc := range testCases { 60 | t.Run(fmt.Sprintf("%d", tc.in), func(t *testing.T) { 61 | sp := sRGBToLinear(tc.in) 62 | if math.Abs(tc.out-sp) > 0.05 { 63 | t.Fatalf("got %f, wanted %f", sp, tc.out) 64 | } 65 | }) 66 | } 67 | } 68 | --------------------------------------------------------------------------------