Add ability to tune hashing algorithm and image resolution

Closes #2

Signed-off-by: Igor Shishkin <me@teran.ru>

go.mod

@@ -3,7 +3,7 @@ module github.com/teran/imgsum
 go 1.13
 
 require (
-	github.com/Soreil/arw v0.0.0-20180907190942-c71045f5319b
+	github.com/soreil/arw v0.0.0-20180907190942-c71045f5319b
 	github.com/bamiaux/rez v0.0.0-20170731184118-29f4463c688b
 	github.com/brett-lempereur/ish v0.0.0-20161214150457-bbdc45bcf55d
 	github.com/gonum/blas v0.0.0-20181208220705-f22b278b28ac

image/hasher.go

@@ -0,0 +1,29 @@
+package image
+
+import (
+	"fmt"
+
+	"github.com/brett-lempereur/ish"
+)
+
+// HashType type to represent the list of hashers available
+type HashType string
+
+var (
+	// HashTypeAvg reflects AverageHash
+	HashTypeAvg HashType = "avg"
+
+	// HashTypeDiff reflects DiffrenceHash
+	HashTypeDiff HashType = "diff"
+)
+
+func getHasher(kind HashType, res int) (ish.PerceptualHash, error) {
+	switch kind {
+	case HashTypeAvg:
+		return ish.NewAverageHash(res, res), nil
+	case HashTypeDiff:
+		return ish.NewDifferenceHash(res, res), nil
+	default:
+		return nil, fmt.Errorf("Unknown hasher: %s", kind)
+	}
+}

image/image.go

@@ -9,9 +9,8 @@ import (
 	"os"
 	"regexp"
 
-	"github.com/Soreil/arw"
-	"github.com/brett-lempereur/ish"
 	"github.com/nf/cr2"
+	"github.com/soreil/arw"
 )
 
 var (
@@ -117,8 +116,8 @@ func (i *Image) openSonyRaw() error {
 
 // Hexdigest produces image hash and returns it as string
 // actually the string is SHA256 from the hasher's value
-func (i *Image) Hexdigest() (string, error) {
-	hasher := ish.NewAverageHash(1024, 1024)
+func (i *Image) Hexdigest(hashKind HashType, res int) (string, error) {
+	hasher, err := getHasher(hashKind, res)
 	dh, err := hasher.Hash(i.image)
 	if err != nil {
 		return "", err

main.go

@@ -32,15 +32,15 @@ var (
 	date    = "0000-00-00T00:00:00Z"
 )
 
-func calculate(file string) error {
+func calculate(file string, hashKind image.HashType, res int) error {
 	i, err := image.NewImage(file)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, file, err.Error())
 		wg.Done()
 		return err
 	}
 
-	h, err := i.Hexdigest()
+	h, err := i.Hexdigest(hashKind, res)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, file, err.Error())
 		wg.Done()
@@ -117,6 +117,10 @@ func main() {
 		fmt.Printf("    Read file list from stdin as a JSON({'files':['file1', 'file2']}) and calculate their hash\n")
 		fmt.Printf("  -json-output\n")
 		fmt.Printf("    Return duplicates as a JSON(useful for IPC)\n")
+		fmt.Printf("  -hash-kind avg|diff")
+		fmt.Printf("    Allows to set hash function: average or difference (avg by default)")
+		fmt.Printf("  -hash-resolution 1024")
+		fmt.Printf("    Allows to set the (squared) image resolution to pass to hashing function (1024 by default)")
 		fmt.Printf("  -version\n")
 		fmt.Printf("    Print imgsum version\n\n")
 		fmt.Printf("Examples:\n")
@@ -132,6 +136,8 @@ func main() {
 	json_input := flag.Bool("json-input", false, "")
 	json_output := flag.Bool("json-output", false, "")
 	versionFlag := flag.Bool("version", false, "")
+	hashKind := flag.String("hash-kind", "avg", "")
+	hashResolution := flag.Int("hash-resolution", 1024, "")
 
 	flag.Parse()
 	if flag.NArg() < 1 && !*json_input && !*versionFlag {
@@ -168,7 +174,7 @@ func main() {
 			filename := files[file]
 			wg.Add(1)
 			go func() {
-				calculate(filename)
+				calculate(filename, image.HashType(*hashKind), *hashResolution)
 				defer func() {
 					<-sem
 				}()