Import existing source code

.gitignore

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+.idea
+
+idicon

Dockerfile

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+FROM golang:1.16-alpine AS build-env
+
+ENV USER=appuser
+ENV UID=8000
+
+RUN adduser \
+    --disabled-password \
+    --gecos "" \
+    --home "/null" \
+    --shell "/sbin/nologin" \
+    --no-create-home \
+    --uid "${UID}" \
+    "${USER}"
+
+WORKDIR /tmp/build
+ADD . /tmp/build
+# -ldlflags '-s' to strip binary
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o app -ldflags '-w -s'
+
+###
+
+FROM scratch
+
+COPY --from=build-env /etc/passwd /etc/passwd
+COPY --from=build-env /etc/group /etc/group
+COPY --from=build-env /tmp/build/app /usr/local/bin/idicon
+
+USER appuser:appuser
+
+EXPOSE 8000
+
+ENTRYPOINT ["/usr/local/bin/idicon"]

LICENSE

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+The MIT License
+
+Copyright (c) 2021 Paul-Christian Volkmer
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.adoc

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+= IdIcon
+
+Simple implementation of an identicon service.
+
+== Usage
+
+HTTP `GET` is used to request an identicon image.
+
+....
+curl http://localhost:8000/avatar/23463b99b62a72f26ed677cc556c44e8?s=100&c=v2
+....
+
+Instead of requesting identicons for MD5 hashes of usernames or mail addresses, it is possible to use plain username and mail address. The will result in the same generated identicon.
+
+Use request query parameter `s` to request images with specified size. Default value is 80px. The size is limited to a maximum value of 512px.
+Query parameter `c` will set color scheme. Available values are `v1` and `v2`.
+
+=== Server settings
+
+You can use `COLORSCHEME` in environment to define the default color scheme to be used. Fallback value will be `v2`.
+
+== Development and local start
+
+A *Golang* setup is required for development. File `idicon.go` contains the source code. Type
+
+....
+$ go run
+....
+
+to run the application on port 8000.
+
+=== Docker build
+
+Use `Dockerfile` to build a new image based on `scratch` image and start this image by typing
+
+....
+$ docker build -t idicon .
+$ docker run -p 8000:8000 idicon
+....
+
+This will build the image and will start a new container listening on port 8000 for requests.

go.mod

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+module idicon
+
+go 1.16
+
+require github.com/gorilla/mux v1.8.0

go.sum

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+github.com/gorilla/mux v1.8.0 h1:i40aqfkR1h2SlN9hojwV5ZA91wcXFOvkdNIeFDP5koI=
+github.com/gorilla/mux v1.8.0/go.mod h1:DVbg23sWSpFRCP0SfiEN6jmj59UnW/n46BH5rLB71So=

idicon.go

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+package main
+
+import (
+	"crypto/md5"
+	"encoding/hex"
+	"github.com/gorilla/mux"
+	"image"
+	"image/color"
+	"image/draw"
+	"image/png"
+	"log"
+	"net/http"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+func colorV1(hash [16]byte) color.RGBA {
+	r := 32 + (hash[0]%16)/2<<4
+	g := 32 + (hash[2]%16)/2<<4
+	b := 32 + (hash[len(hash)-1]%16)/2<<4
+
+	if r > g && r > b {
+		r += 48
+	} else if g > r && g > b {
+		g += 48
+	} else if b > r && b > g {
+		b += 48
+	}
+	return color.RGBA{r, g, b, 255}
+}
+
+func colorV2(hash [16]byte) color.RGBA {
+	var palette = []color.RGBA{
+		{0x3c, 0x38, 0x36, 0xff},
+		{0xcc, 0x24, 0x1d, 0xff},
+		{0x98, 0x97, 0x1a, 0xff},
+		{0xd7, 0x99, 0x21, 0xff},
+		{0x45, 0x85, 0x88, 0xff},
+		{0xb1, 0x62, 0x86, 0xff},
+		{0x68, 0x9d, 0x6a, 0xff},
+		{0xa8, 0x99, 0x84, 0xff},
+	}
+	return palette[hash[15]%8]
+}
+
+func genIdIcon(id string, size int, f func([16]byte) color.RGBA) *image.NRGBA {
+	id = strings.ToLower(id)
+	blocks := 5
+	if size > 512 {
+		size = 512
+	}
+
+	hash := hashBytes(id)
+	data := make([]bool, blocks*blocks)
+	for i := 0; i < len(hash)-1; i++ {
+		data[i] = hash[i]%2 != hash[i+1]%2
+	}
+	return drawImage(mirrorData(data, blocks), blocks, size, f(hash))
+}
+
+func hashBytes(id string) [16]byte {
+	hash := [16]byte{}
+	md5RegExp := regexp.MustCompile("[a-f0-9]{32}")
+	if !md5RegExp.Match([]byte(id)) {
+		hash = md5.Sum([]byte(id))
+	} else {
+		dec, _ := hex.DecodeString(id)
+		for idx, b := range dec {
+			hash[idx] = b
+		}
+	}
+	return hash
+}
+
+func mirrorData(data []bool, blocks int) []bool {
+	for x := 0; x < blocks; x++ {
+		min := x*blocks + 1
+		for y := 0; y < blocks; y++ {
+			a := ((blocks - x - 1) * blocks) + y
+			b := min + y - 1
+			if data[a] {
+				data[b] = true
+			}
+		}
+	}
+	return data
+}
+
+func drawImage(data []bool, blocks int, size int, c color.Color) *image.NRGBA {
+	img := image.NewNRGBA(image.Rect(0, 0, size, size))
+
+	draw.Draw(img, img.Bounds(), &image.Uniform{color.Gray{240}}, image.Point{0, 0}, draw.Src)
+
+	blockSize := size / (blocks + 1)
+	border := (size - (blocks * blockSize)) / 2
+
+	for x := border; x < blockSize*blocks+border; x++ {
+		bx := (x - border) / blockSize
+		for y := border; y < blockSize*blocks+border; y++ {
+			by := (y - border) / blockSize
+			idx := bx*blocks + by
+			if data[idx] && (bx < blocks || by < blocks) {
+				img.Set(x, y, c)
+			}
+		}
+	}
+
+	return img
+}
+
+func RequestHandler(w http.ResponseWriter, r *http.Request) {
+	id := mux.Vars(r)["id"]
+
+	size, err := strconv.Atoi(r.URL.Query().Get("s"))
+	if err != nil {
+		size = 80
+	}
+
+	colorScheme := r.URL.Query().Get("c")
+	if colorScheme == "" {
+		colorScheme = os.Getenv("COLORSCHEME")
+	}
+
+	w.Header().Add("Content-Type", "image/png")
+	if colorScheme == "v1" {
+		err = png.Encode(w, genIdIcon(id, size, colorV1))
+	} else {
+		err = png.Encode(w, genIdIcon(id, size, colorV2))
+	}
+}
+
+func main() {
+	router := mux.NewRouter()
+	router.HandleFunc("/avatar/{id}", RequestHandler)
+	log.Fatal(http.ListenAndServe(":8000", router))
+}

idicon_test.go

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+package main
+
+import (
+	"bytes"
+	_ "embed"
+	"github.com/gorilla/mux"
+	"image/png"
+	"net/http"
+	"net/http/httptest"
+	"reflect"
+	"testing"
+)
+
+//go:embed testdata/1a79a4d60de6718e8e5b326e338ae533_v1.png
+var v1 []byte
+
+//go:embed testdata/1a79a4d60de6718e8e5b326e338ae533_v2.png
+var v2 []byte
+
+func testRouter() *mux.Router {
+	router := mux.NewRouter()
+	router.HandleFunc("/avatar/{id}", RequestHandler)
+	return router
+}
+
+func TestCorrectContentType(t *testing.T) {
+	req, err := http.NewRequest("GET", "/avatar/example", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rr := httptest.NewRecorder()
+	testRouter().ServeHTTP(rr, req)
+
+	if ctype := rr.Header().Get("Content-Type"); ctype != "image/png" {
+		t.Errorf("content type header does not match: got %v want image/png", ctype)
+	}
+}
+
+func TestCorrectResponseForV1ColorScheme(t *testing.T) {
+	req, err := http.NewRequest("GET", "/avatar/1a79a4d60de6718e8e5b326e338ae533?c=v1", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rr := httptest.NewRecorder()
+	testRouter().ServeHTTP(rr, req)
+
+	if !reflect.DeepEqual(rr.Body.Bytes(), v1) {
+		t.Errorf("returned image does not match expected image")
+	}
+}
+
+func TestCorrectResponseForV2ColorScheme(t *testing.T) {
+	req, err := http.NewRequest("GET", "/avatar/1a79a4d60de6718e8e5b326e338ae533?c=v2", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rr := httptest.NewRecorder()
+	testRouter().ServeHTTP(rr, req)
+
+	if !reflect.DeepEqual(rr.Body.Bytes(), v2) {
+		t.Errorf("returned image does not match expected image")
+	}
+}
+
+func TestIgnoreCase(t *testing.T) {
+	w1 := bytes.NewBuffer([]byte{})
+	png.Encode(w1, genIdIcon("example", 80, colorV1))
+
+	w2 := bytes.NewBuffer([]byte{})
+	png.Encode(w2, genIdIcon("Example", 80, colorV1))
+
+	if bytes.Compare(w1.Bytes(), w2.Bytes()) != 0 {
+		t.Errorf("resulting images do not match")
+	}
+}
+
+func TestStringMatchesHash(t *testing.T) {
+	w1 := bytes.NewBuffer([]byte{})
+	// MD5 of lowercase 'example'
+	png.Encode(w1, genIdIcon("1a79a4d60de6718e8e5b326e338ae533", 80, colorV2))
+
+	w2 := bytes.NewBuffer([]byte{})
+	png.Encode(w2, genIdIcon("Example", 80, colorV2))
+
+	if bytes.Compare(w1.Bytes(), w2.Bytes()) != 0 {
+		t.Errorf("resulting images do not match")
+	}
+}