libtuning: Improve filename parsing

In the tuning datasets, the files had names like
'imx335_1600l_3000k_1.dng'. That failed on the old filename parsing
function. As there is no need to dictate the order of the tags, split
the big regex into chunks and parse them one by one. This also makes
the code easier to digest.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

utils/tuning/libtuning/utils.py

@@ -43,16 +43,30 @@ def _list_image_files(directory):
 
 
 def _parse_image_filename(fn: Path):
-    result = re.search(r'^(alsc_)?(\d+)[kK]_(\d+)?[lLuU]?.\w{3,4}$', fn.name)
+    lsc_only = False
-    if result is None:
+    color_temperature = None
-        logger.error(f'The file name of {fn.name} is incorrectly formatted')
+    lux = None
-        return None, None, None
 
-    color = int(result.group(2))
+    parts = fn.stem.split('_')
-    lsc_only = result.group(1) is not None
+    for part in parts:
-    lux = None if lsc_only else int(result.group(3))
+        if part == 'alsc':
+            lsc_only = True
+            continue
+        r = re.match(r'(\d+)[kK]', part)
+        if r:
+            color_temperature = int(r.group(1))
+            continue
+        r = re.match(r'(\d+)[lLuU]', part)
+        if r:
+            lux = int(r.group(1))
 
-    return color, lux, lsc_only
+    if color_temperature is None:
+        logger.error(f'The file name of "{fn.name}" does not contain a color temperature')
+
+    if lux is None and lsc_only is False:
+        logger.error(f'The file name of "{fn.name}" must either contain alsc or a lux level')
+
+    return color_temperature, lux, lsc_only
 
 
 # \todo Implement this from check_imgs() in ctt.py