add meme backflip (#25)

Author: MeetWq

meme_generator_memes/src/memes.rs

@@ -17,6 +17,7 @@ mod atri_pillow;
 mod ayachi_holdsign;
 mod ba_say;
 mod back_to_work;
+mod backflip;
 mod bad_news;
 mod batitle;
 mod beat_head;

meme_generator_memes/src/memes/backflip.rs

@@ -0,0 +1,94 @@
+use core::f32;
+use skia_safe::{Image, Matrix};
+
+use meme_generator_core::error::Error;
+use meme_generator_utils::{
+    builder::InputImage,
+    encoder::{FrameAlign, GifInfo, make_gif_or_combined_gif},
+    tools::{local_date, new_surface},
+};
+
+use crate::{options::NoOptions, register_meme};
+
+fn backflip(images: Vec<InputImage>, _: Vec<String>, _: NoOptions) -> Result<Vec<u8>, Error> {
+    let img = &images[0].image;
+    let img_w = img.width();
+    let img_h = img.height();
+
+    let length = ((img_w * img_w + img_h * img_h) as f32).sqrt();
+    let frame_w = (length * 1.3) as i32;
+    let bounce_h = img_h as f32 * 1.2;
+    let frame_h = (bounce_h + length / 2.0 + img_h as f32 * 0.6) as i32;
+    let center_x = (frame_w / 2) as f32;
+    let ground_y = (frame_h - img_h / 2) as f32;
+
+    let total_frames = 30;
+    let bounce1_range = 0.0..0.3;
+    let bounce2_range = 0.3..0.6;
+    let rise_range = 0.6..0.65;
+    let flip_range = 0.65..0.95;
+    let land_range = 0.95..1.0;
+
+    let func = move |i: usize, images: Vec<Image>| {
+        let t = i as f32 / total_frames as f32;
+
+        let (y, angle) = if bounce1_range.contains(&t) {
+            let local_t = (t - bounce1_range.start) / (bounce1_range.end - bounce1_range.start);
+            let y = -4.0 * bounce_h * (local_t - 0.5).powi(2) + bounce_h;
+            let rot = 45.0 * (1.0 - 2.0 * (local_t - 0.5).abs());
+            (ground_y - y, rot)
+        } else if bounce2_range.contains(&t) {
+            let local_t = (t - bounce2_range.start) / (bounce2_range.end - bounce2_range.start);
+            let y = -4.0 * bounce_h * (local_t - 0.5).powi(2) + bounce_h;
+            let rot = -45.0 * (1.0 - 2.0 * (local_t - 0.5).abs());
+            (ground_y - y, rot)
+        } else if rise_range.contains(&t) {
+            let local_t = (t - rise_range.start) / (rise_range.end - rise_range.start);
+            let y = bounce_h - bounce_h * (1.0 - local_t).powi(2);
+            (ground_y - y, 0.0)
+        } else if flip_range.contains(&t) {
+            let local_t = (t - flip_range.start) / (flip_range.end - flip_range.start);
+            let y = bounce_h;
+            let rot = 360.0 * local_t;
+            (ground_y - y, rot)
+        } else if land_range.contains(&t) {
+            let local_t = (t - land_range.start) / (land_range.end - land_range.start);
+            let y = bounce_h - bounce_h * local_t.powi(2);
+            (ground_y - y, 0.0)
+        } else {
+            (ground_y, 0.0)
+        };
+
+        let img = &images[0];
+        let mut surface = new_surface((frame_w, frame_h));
+        let canvas = surface.canvas();
+        let mut matrix = Matrix::new_identity();
+        matrix.pre_translate((center_x, y));
+        matrix.pre_rotate(angle, None);
+        matrix.pre_translate((-img_w as f32 / 2.0, -img_h as f32 / 2.0));
+        canvas.concat(&matrix);
+        canvas.draw_image(img, (0, 0), None);
+
+        Ok(surface.image_snapshot())
+    };
+
+    make_gif_or_combined_gif(
+        images,
+        func,
+        GifInfo {
+            frame_num: total_frames,
+            duration: 0.05,
+        },
+        FrameAlign::ExtendLoop,
+    )
+}
+
+register_meme!(
+    "backflip",
+    backflip,
+    min_images = 1,
+    max_images = 1,
+    keywords = &["后空翻"],
+    date_created = local_date(2025, 6, 29),
+    date_modified = local_date(2025, 6, 29),
+);