add meme backflip (#274)

Author: MeetWq

meme_generator/memes/backflip/__init__.py

@@ -0,0 +1,81 @@
+import math
+from datetime import datetime
+from pathlib import Path
+
+from pil_utils import BuildImage
+
+from meme_generator import add_meme
+from meme_generator.utils import FrameAlignPolicy, Maker, make_gif_or_combined_gif
+
+img_dir = Path(__file__).parent / "images"
+
+
+def backflip(images: list[BuildImage], texts, args):
+    img_w, img_h = images[0].size
+    length = math.sqrt(img_w * img_w + img_h * img_h)
+    frame_w = int(length * 1.3)
+    bounce_h = img_h * 1.2
+    frame_h = int(bounce_h + length / 2 + img_h * 0.6)
+    center_x = frame_w / 2
+    ground_y = frame_h - img_h / 2
+
+    total_frames = 30
+    bounce1_range = (0.0, 0.3)
+    bounce2_range = (0.3, 0.6)
+    rise_range = (0.6, 0.65)
+    flip_range = (0.65, 0.95)
+    land_range = (0.95, 1.0)
+
+    def maker(i: int) -> Maker:
+        def make(imgs: list[BuildImage]) -> BuildImage:
+            t = i / total_frames
+
+            if bounce1_range[0] <= t < bounce1_range[1]:
+                local_t = (t - bounce1_range[0]) / (bounce1_range[1] - bounce1_range[0])
+                y = -4 * bounce_h * (local_t - 0.5) ** 2 + bounce_h
+                rot = 45 * (1 - 2 * abs(local_t - 0.5))
+            elif bounce2_range[0] <= t < bounce2_range[1]:
+                local_t = (t - bounce2_range[0]) / (bounce2_range[1] - bounce2_range[0])
+                y = -4 * bounce_h * (local_t - 0.5) ** 2 + bounce_h
+                rot = -45 * (1 - 2 * abs(local_t - 0.5))
+            elif rise_range[0] <= t < rise_range[1]:
+                local_t = (t - rise_range[0]) / (rise_range[1] - rise_range[0])
+                y = bounce_h - bounce_h * (1 - local_t) ** 2
+                rot = 0.0
+            elif flip_range[0] <= t < flip_range[1]:
+                local_t = (t - flip_range[0]) / (flip_range[1] - flip_range[0])
+                y = bounce_h
+                rot = 360 * local_t
+            elif land_range[0] <= t < land_range[1]:
+                local_t = (t - land_range[0]) / (land_range[1] - land_range[0])
+                y = bounce_h - bounce_h * local_t**2
+                rot = 0.0
+            else:
+                y = ground_y
+                rot = 0.0
+
+            frame = BuildImage.new("RGBA", (frame_w, frame_h))
+            img = imgs[0].convert("RGBA").rotate(-rot, expand=True)
+            frame.paste(
+                img,
+                (int(center_x - img.width / 2), int(ground_y - y - img.height / 2)),
+                alpha=True,
+            )
+            return frame
+
+        return make
+
+    return make_gif_or_combined_gif(
+        images, maker, total_frames, 0.05, FrameAlignPolicy.extend_loop
+    )
+
+
+add_meme(
+    "backflip",
+    backflip,
+    min_images=1,
+    max_images=1,
+    keywords=["后空翻"],
+    date_created=datetime(2025, 6, 29),
+    date_modified=datetime(2025, 6, 29),
+)