more refactoring

filetypes/filetypes.go

@@ -2,6 +2,10 @@ package filetypes
 
 import (
 	"fmt"
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
 
 	tk "modernc.org/tk9.0"
 )
@@ -95,3 +99,19 @@ func GetTkTypes(fds []FileDescription) []tk.FileType {
 	}
 	return fts
 }
+
+func IsImage(entry os.DirEntry) bool {
+	if entry.IsDir() {
+		return false
+	}
+	ext := filepath.Ext(entry.Name())
+	if ext == "" {
+		return false
+	}
+	for _, ft := range Valid {
+		if slices.Contains(ft.MacExtensions, strings.ToLower(ext[1:])) {
+			return true
+		}
+	}
+	return false
+}