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October 7, 2020 15:13
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A simple way to render an icon based on a hash
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/* | |
Copyright (c) 2013, Damian Gryski <[email protected]> | |
All rights reserved. | |
Redistribution and use in source and binary forms, with or without | |
modification, are permitted provided that the following conditions are met: | |
* Redistributions of source code must retain the above copyright notice, | |
this list of conditions and the following disclaimer. | |
* Redistributions in binary form must reproduce the above copyright notice, | |
this list of conditions and the following disclaimer in the documentation | |
and/or other materials provided with the distribution. | |
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND | |
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED | |
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE | |
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE | |
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR | |
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER | |
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, | |
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
*/ | |
// Package identicon creates simple visual hashes of data as PNGs. | |
/* | |
For more information, see https://en.wikipedia.org/wiki/Identicon and https://github.com/blog/1586-identicons | |
*/ | |
package main | |
import ( | |
"bytes" | |
"fmt" | |
"hash" | |
"image" | |
"image/color" | |
"image/png" | |
"os" | |
"github.com/dchest/siphash" | |
) | |
func main() { | |
r := New7x7([]byte("hi, this is the key")) | |
res := r.Render([]byte("aaa dorld, how are you today?")) | |
fmt.Println(res) | |
img, _, err := image.Decode(bytes.NewBuffer(res)) | |
if err != nil { | |
// Handle error | |
} | |
f, err := os.Create("outimage.png") | |
if err != nil { | |
// Handle error | |
} | |
defer f.Close() | |
// Encode to `PNG` with `DefaultCompression` level | |
// then save to file | |
err = png.Encode(f, img) | |
if err != nil { | |
// Handle error | |
} | |
} | |
// Renderer allows rendering of data as a PNG identicon | |
type Renderer interface { | |
// Render generates a PNG from data | |
Render(data []byte) []byte | |
} | |
type identicon struct { | |
key []byte | |
sqSize int | |
rows int | |
cols int | |
h hash.Hash64 | |
} | |
const xborder = 35 | |
const yborder = 35 | |
const maxX = 420 | |
const maxY = 420 | |
// New5x5 creates a new 5-by-5 identicon renderer using 'key' as the hash salt | |
func New5x5(key []byte) Renderer { | |
return &identicon{ | |
sqSize: 70, | |
rows: 5, | |
cols: 5, | |
h: siphash.New(key), | |
} | |
} | |
// New7x7 creates a new 7-by-7 identicon renderer using 'key' as the hash salt | |
func New7x7(key []byte) Renderer { | |
return &identicon{ | |
sqSize: 50, | |
rows: 7, | |
cols: 7, | |
h: siphash.New(key), | |
} | |
} | |
func (icon *identicon) Render(data []byte) []byte { | |
icon.h.Reset() | |
icon.h.Write(data) | |
h := icon.h.Sum64() | |
nrgba := color.NRGBA{ | |
R: uint8(h), | |
G: uint8(h >> 8), | |
B: uint8(h >> 16), | |
A: 0xff, | |
} | |
h >>= 24 | |
img := image.NewPaletted(image.Rect(0, 0, maxX, maxY), color.Palette{color.NRGBA{0xf0, 0xf0, 0xf0, 0xff}, nrgba}) | |
sqx := 0 | |
sqy := 0 | |
pixels := make([]byte, icon.sqSize) | |
for i := 0; i < icon.sqSize; i++ { | |
pixels[i] = 1 | |
} | |
for i := 0; i < icon.rows*(icon.cols+1)/2; i++ { | |
if h&1 == 1 { | |
for i := 0; i < icon.sqSize; i++ { | |
x := xborder + sqx*icon.sqSize | |
y := yborder + sqy*icon.sqSize + i | |
offs := img.PixOffset(x, y) | |
copy(img.Pix[offs:], pixels) | |
x = xborder + (icon.cols-1-sqx)*icon.sqSize | |
offs = img.PixOffset(x, y) | |
copy(img.Pix[offs:], pixels) | |
} | |
} | |
h >>= 1 | |
sqy++ | |
if sqy == icon.rows { | |
sqy = 0 | |
sqx++ | |
} | |
} | |
var buf bytes.Buffer | |
png.Encode(&buf, img) | |
return buf.Bytes() | |
} |
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