AI: Added some intelligence to label loading.

Now when loading labels internal/ai/tensorflow package will try to look
for all the files that match the glob label*.txt and will return the
labels that match the expected number. Some models add a first label
called background, which is a bias.
Also, a new parameter has been added to models to allow a second path to
look for the label files. This path is set to nasnet asset on
internal/ai/vision.

internal/ai/tensorflow/labels.go

@@ -2,19 +2,17 @@ package tensorflow
 
 import (
 	"bufio"
+	"io/fs"
 	"os"
+	"path/filepath"
 )
 
-// LoadLabels loads the labels of classification models from the specified path and returns them.
-func LoadLabels(modelPath string) (labels []string, err error) {
-	modelLabels := modelPath + "/labels.txt"
-
-	log.Infof("tensorflow: loading model labels from labels.txt")
-
-	f, err := os.Open(modelLabels)
+func loadLabelsFromPath(path string) (labels []string, err error) {
+	log.Infof("tensorflow: loading model labels from %s", path)
 
+	f, err := os.Open(path)
 	if err != nil {
-		return labels, err
+		return nil, err
 	}
 
 	defer f.Close()
@@ -30,3 +28,34 @@ func LoadLabels(modelPath string) (labels []string, err error) {
 
 	return labels, err
 }
+
+// LoadLabels loads the labels of classification models from the specified path and returns them.
+func LoadLabels(modelPath string, expectedLabels int) (labels []string, err error) {
+
+	dir := os.DirFS(modelPath)
+	matches, err := fs.Glob(dir, "labels*.txt")
+	if err != nil {
+		return nil, err
+	}
+
+	for i := range matches {
+		labels, err := loadLabelsFromPath(filepath.Join(modelPath, matches[i]))
+		if err != nil {
+			return nil, err
+		}
+
+		switch expectedLabels - len(labels) {
+		case 0:
+			log.Infof("Found a valid labels file: %s", matches[i])
+			return labels, nil
+		case 1:
+			log.Infof("Found a valid labels file %s but we have to add bias", matches[i])
+
+			return append([]string{"background"}, labels...), nil
+		default:
+			log.Infof("File not valid. Expected %d labels and have %d",
+				expectedLabels, len(labels))
+		}
+	}
+	return nil, os.ErrNotExist
+}