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package main
import (
"bytes"
"crypto/sha256"
"errors"
"image"
"image/color"
_ "image/gif"
_ "image/jpeg"
"image/png"
"math"
"sync"
"golang.org/x/image/draw"
_ "golang.org/x/image/webp"
)
const avatarSize = 256
var decoding sync.Mutex
func cropAvatar(data []byte, x, y, size int) ([]byte, error) {
cfg, _, err := image.DecodeConfig(bytes.NewReader(data))
if err != nil {
return nil, errors.New("Avatar must be a PNG, JPEG, GIF or WebP image")
}
if cfg.Width > 6000 || cfg.Height > 6000 || cfg.Width*cfg.Height > 16_000_000 {
return nil, errors.New("Avatar image is too large, keep it under 16 megapixels")
}
decoding.Lock()
defer decoding.Unlock()
img, _, err := image.Decode(bytes.NewReader(data))
if err != nil {
return nil, errors.New("Avatar must be a PNG, JPEG, GIF or WebP image")
}
b := img.Bounds()
if size <= 0 || size > b.Dx() || size > b.Dy() {
size = min(b.Dx(), b.Dy())
x = (b.Dx() - size) / 2
y = (b.Dy() - size) / 2
}
x = max(0, min(x, b.Dx()-size))
y = max(0, min(y, b.Dy()-size))
src := image.Rect(b.Min.X+x, b.Min.Y+y, b.Min.X+x+size, b.Min.Y+y+size)
dst := image.NewRGBA(image.Rect(0, 0, avatarSize, avatarSize))
draw.CatmullRom.Scale(dst, dst.Bounds(), img, src, draw.Src, nil)
var out bytes.Buffer
if err := png.Encode(&out, dst); err != nil {
return nil, err
}
return out.Bytes(), nil
}
var blocks = [][][2]float64{
{{0, 0}, {1, 0}, {1, 1}, {0, 1}},
{{0, 0}, {1, 0}, {0, 1}},
{{0, 0}, {1, .5}, {0, 1}},
{{.5, 0}, {1, .5}, {.5, 1}, {0, .5}},
{{.25, .25}, {.75, .25}, {.75, .75}, {.25, .75}},
{{0, 0}, {1, 0}, {.5, .5}},
{{.5, 0}, {1, 1}, {0, 1}},
{{0, 0}, {1, 0}, {1, .5}, {0, .5}},
{{0, 0}, {.5, 0}, {1, 1}, {.5, 1}},
{{0, .5}, {.5, 0}, {1, .5}, {1, 1}, {0, 1}},
}
var centres = []int{0, 3, 4}
func identicon(seed string) []byte {
sum := sha256.Sum256([]byte(seed))
h := float64(uint16(sum[28])<<8|uint16(sum[29])) / 65536
fg := hsl(h, 0.5+float64(sum[30])/255*0.2, 0.42+float64(sum[31])/255*0.12)
const pad, cell = 14, 76
img := image.NewRGBA(image.Rect(0, 0, avatarSize, avatarSize))
draw.Draw(img, img.Bounds(), &image.Uniform{color.RGBA{255, 255, 255, 255}}, image.Point{}, draw.Src)
corner, side := int(sum[0])%len(blocks), int(sum[1])%len(blocks)
cornerTurn, sideTurn := int(sum[2])%4, int(sum[3])%4
centre := centres[int(sum[4])%len(centres)]
invert := sum[5]&1 == 1
place := func(shape, col, row, turn int, flip bool) {
poly := blocks[shape]
for y := 0; y < cell; y++ {
for x := 0; x < cell; x++ {
u, v := (float64(x)+.5)/cell, (float64(y)+.5)/cell
for i := 0; i < turn; i++ {
u, v = v, 1-u
}
if inside(poly, u, v) != flip {
img.SetRGBA(pad+col*cell+x, pad+row*cell+y, fg)
}
}
}
}
for i, p := range [][2]int{{0, 0}, {2, 0}, {2, 2}, {0, 2}} {
place(corner, p[0], p[1], (cornerTurn+i)%4, false)
}
for i, p := range [][2]int{{1, 0}, {2, 1}, {1, 2}, {0, 1}} {
place(side, p[0], p[1], (sideTurn+i)%4, invert)
}
place(centre, 1, 1, 0, false)
var out bytes.Buffer
png.Encode(&out, img)
return out.Bytes()
}
func inside(poly [][2]float64, x, y float64) bool {
in := false
for i, j := 0, len(poly)-1; i < len(poly); j, i = i, i+1 {
a, b := poly[i], poly[j]
if (a[1] > y) != (b[1] > y) && x < (b[0]-a[0])*(y-a[1])/(b[1]-a[1])+a[0] {
in = !in
}
}
return in
}
func hsl(h, s, l float64) color.RGBA {
q := l + s - l*s
if l < 0.5 {
q = l * (1 + s)
}
p := 2*l - q
ch := func(t float64) uint8 {
t -= math.Floor(t)
switch {
case t < 1.0/6:
return uint8(255 * (p + (q-p)*6*t))
case t < 0.5:
return uint8(255 * q)
case t < 2.0/3:
return uint8(255 * (p + (q-p)*(2.0/3-t)*6))
}
return uint8(255 * p)
}
return color.RGBA{ch(h + 1.0/3), ch(h), ch(h - 1.0/3), 255}
}
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