Prioritize using pywebp if there is no duplicated frame, else use pillow

src/sticker_convert/converter.py

@@ -33,10 +33,16 @@
     "[F] Failed Compression {} -> {}, "
     "cannot get below limit {} with lowest quality under current settings (Best size: {})"
 )
-MSG_PYWEBP = (
-    "WARNING: System WebP>=0.5.0 was not found, hence Pillow cannot be used "
-    "for creating animated webp. Using pywebp instead, which is known to "
-    "collapse same frames into single frame, causing problem with animation timing."
+MSG_PYWEBP_DUPFRAME = (
+    "[W] {} contains duplicated frame.\n"
+    "    System WebP>=0.5.0 was not found, hence Pillow cannot be used\n"
+    "    for creating animated webp. Using pywebp instead, which is known to\n"
+    "    collapse same frames into single frame, causing problem with animation timing."
+)
+MSG_WEBP_PIL_DUPFRAME = (
+    "[W] {} contains duplicated frame.\n"
+    "    Using Pillow to create animated webp to avoid same frames collapse\n"
+    "    into single frame, but this is slower."
 )
 
 YUV_RGB_MATRIX = np.array(
@@ -189,7 +195,8 @@ def __init__(
         self.result_step: Optional[int] = None
 
         self.apngasm = None
-        self.pywebp_warning_displayed = False
+        self.msg_pywebp_dupframe_displayed = False
+        self.msg_webp_pil_dupframe_displayed = False
 
     @staticmethod
     def convert(
@@ -689,16 +696,51 @@ def frames_export(self) -> None:
                 self._frames_export_apng()
             else:
                 self._frames_export_png()
-        elif self.out_f.suffix == ".gif" or (
-            self.out_f.suffix == ".webp" and (PIL_WEBP_ANIM or not is_animated)
-        ):
-            self._frames_export_pil_anim()
         elif self.out_f.suffix == ".webp":
             self._frames_export_webp()
+        elif self.out_f.suffix == ".gif":
+            self._frames_export_pil_anim()
         elif self.out_f.suffix in (".webm", ".mp4", ".mkv") or is_animated:
             self._frames_export_pyav()
         else:
             self._frames_export_pil()
+
+    def _check_dup(self) -> bool:
+        if len(self.frames_processed) == 1:
+            return False
+
+        prev_frame = self.frames_processed[0]
+        for frame in self.frames_processed[1:]:
+            if np.array_equal(frame, prev_frame):
+                return True
+            prev_frame = frame
+
+        return False
+
+    def _frames_export_webp(self) -> None:
+        has_dup_frames = self._check_dup()
+        if self.fps:
+            # It was noted that pywebp would collapse all frames.
+            # aed005b attempted to fix this by creating webp with
+            # variable frame duration. However, the webp created would
+            # not be accepted by WhatsApp.
+            # Therefore, we are preferring Pillow over pywebp.
+            if has_dup_frames:
+                if PIL_WEBP_ANIM:
+                    # Warn that using Pillow is slower
+                    if not self.msg_webp_pil_dupframe_displayed:
+                        self.cb.put(MSG_WEBP_PIL_DUPFRAME.format(self.in_f_name))
+                        self.msg_webp_pil_dupframe_displayed = True
+                    self._frames_export_pil_anim()
+                else:
+                    if not self.msg_pywebp_dupframe_displayed:
+                        self.cb.put(MSG_PYWEBP_DUPFRAME.format(self.in_f_name))
+                        self.msg_pywebp_dupframe_displayed = True
+                    self._frames_export_pywebp()
+            else:
+                self._frames_export_pywebp()
+        else:
+            self._frames_export_pil()
 
     def _frames_export_pil(self) -> None:
         with Image.fromarray(self.frames_processed[0]) as im:  # type: ignore
@@ -799,17 +841,9 @@ def _frames_export_pil_anim(self) -> None:
             **extra_kwargs,
         )
 
-    def _frames_export_webp(self) -> None:
+    def _frames_export_pywebp(self) -> None:
         import webp  # type: ignore
 
-        # It was noted that pywebp would collapse all frames.
-        # aed005b attempted to fix this by creating webp with
-        # variable frame duration. However, the webp created would
-        # not be accepted by WhatsApp.
-        # Therefore, we are preferring Pillow over pywebp.
-        if not self.pywebp_warning_displayed:
-            self.cb.put(MSG_PYWEBP)
-
         assert self.fps
 
         config = webp.WebPConfig.new(quality=self.quality)  # type: ignore