Clean up

2 files changed, 74 insertions, 38 deletions

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..8e6bab1
--- /dev/null
+++ b/README.md
@@ -0,0 +1,32 @@
+# hashimg
+
+Written for Boston Golang "Chopped" meetup. Given the following packages (and
+any of their subpackages), make anything:
+
+* bytes
+* crypto
+* encoding
+* image
+* regexp
+
+Additionally, the following packages from the standard library were available:
+
+* flag
+* fmt
+
+I ended up using all of the "basket" packages, even where not strictly
+necessary; e.g. the only real reason to base64 encode the resulting image is
+just so that we can do something with the encoding package. Likewise, we don't
+_really_ need a regular expression to validate the input, but why not throw it
+in?
+
+Given a "username", this program finds the SHA 256 checksum of the username and
+uses it to generate a GitHub-style default avatar. The first three bytes are
+used to create color A, the next three bytes are used to create color B, and the
+next 25 bytes are used to form a 5x5 pixel grid, with the value being used to
+determine whether the pixel should be colored with A or B.
+
+Next, the 5x5 pixel image is tesselated into a 10x10 pixel image for some neat
+mirroring, and then it is scaled up by a user-provided multiplier.
+
+Finally, the image is base64 encoded and printed to standard output.
diff --git a/main.go b/main.go
index 148ce16..7e59b1b 100644
--- a/main.go
+++ b/main.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	// Bag 4: bytes, crypto, encoding, image, regexp
 	"bytes"
 	"crypto/sha256"
 	"encoding/base64"
@@ -9,54 +10,55 @@ import (
 	"image/png"
 	"regexp"
 
+	// Pantry: flag
 	"flag"
 	"fmt"
-	"strings"
 )
 
-var usernamePattern = regexp.MustCompile("[a-zA-Z][a-zA-Z0-9]+")
+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 strings.TrimSpace(*username) == "" {
+
+	if !usernamePattern.MatchString(*username) {
 		flag.Usage()
 		return
 	}
 
-	if !usernamePattern.MatchString(*username) {
+	if *mult < 1 {
 		flag.Usage()
 		return
 	}
 
-	seed := hash(*username)
-	img := makeBigger(repeat(generateImage(seed)))
-	str, err := encodeImage(img)
+	hash := sha256.Sum256([]byte(*username))
+	img := makeBigger(tesselate(generateImage(hash)), *mult)
+	str, err := encodePNG(img)
 	if err != nil {
-		fmt.Printf("%v\n", err)
+		fmt.Println(err)
 		return
 	}
-	fmt.Println(str)
-}
 
-func hash(username string) [32]byte {
-	return sha256.Sum256([]byte(username))
+	fmt.Println(str)
 }
 
-func generateImage(hash [32]byte) image.Image {
-	img := image.NewNRGBA(image.Rect(0, 0, 5, 5))
-	colorA := color.NRGBA{
-		R: hash[0],
-		G: hash[1],
-		B: hash[2],
-		A: 255,
+func newColor(b []byte) color.NRGBA {
+	if len(b) != 3 {
+		panic("cannot make color without exactly 3 bytes")
 	}
-	colorB := color.NRGBA{
-		R: hash[3],
-		G: hash[4],
-		B: hash[5],
+	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++ {
@@ -72,7 +74,7 @@ func generateImage(hash [32]byte) image.Image {
 	return img
 }
 
-func encodeImage(img image.Image) (string, error) {
+func encodePNG(img *image.NRGBA) (string, error) {
 	var b bytes.Buffer
 	if err := png.Encode(&b, img); err != nil {
 		return "", err
@@ -80,26 +82,28 @@ func encodeImage(img image.Image) (string, error) {
 	return base64.StdEncoding.EncodeToString(b.Bytes()), nil
 }
 
-func repeat(img image.Image) image.Image {
-	newImg := image.NewNRGBA(image.Rect(0, 0, 10, 10))
-	for x := 0; x < 5; x++ {
-		for y := 0; y < 5; y++ {
+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(9-x, y, img.At(x, y))
-			newImg.Set(x, 9-y, img.At(x, y))
-			newImg.Set(9-x, 9-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.Image) image.Image {
-	newImg := image.NewNRGBA(image.Rect(0, 0, 200, 200))
-	for x := 0; x < 10; x++ {
-		for y := 0; y < 10; y++ {
-			for i := 0; i < 20; i++ {
-				for j := 0; j < 20; j++ {
-					newImg.Set(x*20+i, y*20+j, img.At(x, y))
+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))
 				}
 			}
 		}