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package main
import (
// Bag 4: bytes, crypto, encoding, image, regexp
"bytes"
"crypto/sha256"
"encoding/base64"
"image"
"image/color"
"image/png"
"regexp"
// Pantry: flag
"flag"
"fmt"
)
var usernamePattern = regexp.MustCompile("[a-zA-Z][a-zA-Z0-9]*")
func main() {
username := flag.String("username", "", "username to encode as image (must contain only letters a-zA-Z0-9 and start with a letter)")
mult := flag.Int("mult", 20, "the multiplier to apply to the 10x10 generated image (must be >= 1)")
flag.Parse()
if !usernamePattern.MatchString(*username) {
flag.Usage()
return
}
if *mult < 1 {
flag.Usage()
return
}
hash := sha256.Sum256([]byte(*username))
img := makeBigger(tesselate(generateImage(hash)), *mult)
str, err := encodePNG(img)
if err != nil {
fmt.Println(err)
return
}
fmt.Println(str)
}
func newColor(b []byte) color.NRGBA {
if len(b) != 3 {
panic("cannot make color without exactly 3 bytes")
}
return color.NRGBA{
R: b[0],
G: b[1],
B: b[2],
A: 255,
}
}
func generateImage(hash [32]byte) *image.NRGBA {
img := image.NewNRGBA(image.Rect(0, 0, 5, 5))
colorA := newColor(hash[0:3])
colorB := newColor(hash[3:6])
offset := 6
for x := 0; x < 5; x++ {
for y := 0; y < 5; y++ {
on := hash[offset] > 127
color := colorA
if on {
color = colorB
}
img.Set(x, y, color)
offset++
}
}
return img
}
func encodePNG(img *image.NRGBA) (string, error) {
var b bytes.Buffer
if err := png.Encode(&b, img); err != nil {
return "", err
}
return base64.StdEncoding.EncodeToString(b.Bytes()), nil
}
func tesselate(img *image.NRGBA) *image.NRGBA {
newImg := image.NewNRGBA(image.Rect(0, 0, img.Bounds().Max.X*2, img.Bounds().Max.Y*2))
for x := 0; x < img.Bounds().Max.X; x++ {
for y := 0; y < img.Bounds().Max.Y; y++ {
x1 := img.Bounds().Max.X*2 - 1
y1 := img.Bounds().Max.Y*2 - 1
newImg.Set(x, y, img.At(x, y))
newImg.Set(x1-x, y, img.At(x, y))
newImg.Set(x, y1-y, img.At(x, y))
newImg.Set(x1-x, y1-y, img.At(x, y))
}
}
return newImg
}
func makeBigger(img *image.NRGBA, mult int) *image.NRGBA {
newImg := image.NewNRGBA(image.Rect(0, 0, img.Bounds().Max.X*mult, img.Bounds().Max.Y*mult))
for x := 0; x < img.Bounds().Max.X; x++ {
for y := 0; y < img.Bounds().Max.Y; y++ {
for i := 0; i < mult; i++ {
for j := 0; j < mult; j++ {
newImg.Set(x*mult+i, y*mult+j, img.At(x, y))
}
}
}
}
return newImg
}
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