优化 giftool 的截取逻辑

konabot/plugins/image_process/__init__.py

@@ -1,10 +1,10 @@
 import re
 from io import BytesIO
 
+import PIL.Image
 from nonebot import on_message
 from nonebot.adapters import Bot
-from nonebot_plugin_alconna import (Alconna, Args, Image, Option, UniMessage,
-                                    on_alconna)
+from nonebot_plugin_alconna import Alconna, Args, Image, Option, UniMessage, on_alconna
 
 from konabot.common.nb.exc import BotExceptionMessage
 from konabot.common.nb.extract_image import PIL_Image
@@ -29,15 +29,17 @@ def parse_timestamp(tx: str) -> float | None:
     return res
 
 
-cmd_giftool = on_alconna(Alconna(
-    "giftool",
-    Args["img", Image | None],
-    Option("--ss", Args["start_point", str]),
-    Option("--frames:v", Args["frame_count", int]),
-    Option("-t", Args["length", str]),
-    Option("-to", Args["end_point", str]),
-    Option("--speed", Args["speed_factor", float], default=1.0, alias=["-s"]),
-))
+cmd_giftool = on_alconna(
+    Alconna(
+        "giftool",
+        Args["img", Image | None],
+        Option("--ss", Args["start_point", str]),
+        Option("--frames:v", Args["frame_count", int]),
+        Option("-t", Args["length", str]),
+        Option("-to", Args["end_point", str]),
+        Option("--speed", Args["speed_factor", float], default=1.0, alias=["-s"]),
+    )
+)
 
 
 @cmd_giftool.handle()
@@ -80,81 +82,66 @@ async def _(
     if not getattr(image, "is_animated", False):
         raise BotExceptionMessage("错误：输入的不是动图（GIF）")
 
-    frames = []
-    durations = []
-    total_duration = 0.0
-
+    ##
+    # 从这里开始，采样整个 GIF 图
+    frames: list[PIL.Image.Image] = []
+    durations: list[float] = []
     try:
         for i in range(getattr(image, "n_frames")):
             image.seek(i)
             frames.append(image.copy())
-            duration = image.info.get("duration", 100)  # 单位：毫秒
+            duration = image.info.get("duration", 100) / 1000
             durations.append(duration)
-            total_duration += duration / 1000.0  # 转为秒
     except EOFError:
         pass
-
     if not frames:
         raise BotExceptionMessage("错误：读取 GIF 帧失败")
+    # 采样结束
 
-    def time_to_frame_index(target_time: float) -> int:
-        if target_time <= 0:
-            return 0
-        cum = 0.0
-        for idx, dur in enumerate(durations):
-            cum += dur / 1000.0
-            if cum >= target_time:
-                return min(idx, len(frames) - 1)
-        return len(frames) - 1
-    start_frame = 0
-    end_frame = len(frames) - 1
-    if ss is not None:
-        start_frame = time_to_frame_index(ss)
-    if to is not None:
-        end_frame = time_to_frame_index(to)
-        if end_frame < start_frame:
-            end_frame = start_frame
-    elif t is not None:
-        end_time = (ss or 0.0) + t
-        end_frame = time_to_frame_index(end_time)
-        if end_frame < start_frame:
-            end_frame = start_frame
+    ##
+    # 根据开始、结束时间或者帧数量来裁取 GIF 图
 
-    start_frame = max(0, start_frame)
-    end_frame = min(len(frames) - 1, end_frame)
-    selected_frames = frames[start_frame : end_frame + 1]
-    selected_durations = durations[start_frame : end_frame + 1]
+    begin_time = ss or 0
+    end_time = sum(durations)
+    end_time = min(begin_time + (t or end_time), to or end_time, end_time)
 
-    if frame_count is not None and frame_count > 0:
-        if frame_count >= len(selected_frames):
-            pass
-        else:
-            step = len(selected_frames) / frame_count
-            sampled_frames = []
-            sampled_durations = []
-            for i in range(frame_count):
-                idx = int(i * step)
-                sampled_frames.append(selected_frames[idx])
-                sampled_durations.append(
-                    sum(selected_durations) // len(selected_durations)
-                )
-            selected_frames = sampled_frames
-            selected_durations = sampled_durations
+    accumulated = 0.0
+    status = 0
 
-    output_img = BytesIO()
+    sel_frames: list[PIL.Image.Image] = []
+    sel_durations: list[float] = []
 
-    adjusted_durations = [
-        dur / speed_factor for dur in selected_durations
-    ]
+    for i in range(len(frames)):
+        frame = frames[i]
+        duration = durations[i]
+
+        if status == 0:
+            if accumulated + duration > begin_time:
+                status = 1
+                sel_frames.append(frame)
+                sel_durations.append(accumulated + duration - begin_time)
+        elif status == 1:
+            if accumulated + duration > end_time:
+                sel_frames.append(frame)
+                sel_durations.append(end_time - accumulated)
+                break
+            sel_frames.append(frame)
+            sel_durations.append(duration)
+
+        accumulated += duration
+
+    ##
+    # 加速！
+    sel_durations = [dur / speed_factor * 1000 for dur in durations]
 
     rframes = []
     rdur = []
 
     acc_mod_20 = 0
 
-    for i in range(len(selected_frames)):
-        fr = selected_frames[i]
-        du: float = adjusted_durations[i]
+    for i in range(len(sel_frames)):
+        fr = sel_frames[i]
+        du = round(sel_durations[i])
 
         if du >= 20:
             rframes.append(fr)
@@ -170,10 +157,12 @@ async def _(
                 if acc_mod_20 >= 20:
                     acc_mod_20 = 0
 
-    if len(rframes) == 1 and len(selected_frames) > 1:
-        rframes.append(selected_frames[max(2, len(selected_frames) // 2)])
+    if len(rframes) == 1 and len(sel_frames) > 1:
+        rframes.append(sel_frames[max(2, len(sel_frames) // 2)])
         rdur.append(20)
 
+    ##
+    # 收尾：看看透明度这块
     transparency_flag = False
     for f in rframes:
         if f.mode == "RGBA":
@@ -186,12 +175,13 @@ async def _(
 
     tf = {}
     if transparency_flag:
-        tf['transparency'] = 0
+        tf["transparency"] = 0
 
     if is_rev:
         rframes = rframes[::-1]
         rdur = rdur[::-1]
 
+    output_img = BytesIO()
     if rframes:
         rframes[0].save(
             output_img,