add meme sphere_rotate (#275)

Author: MeetWq

meme_generator/memes/sphere_rotate/__init__.py

@@ -0,0 +1,166 @@
+import math
+import struct
+from datetime import datetime
+
+import skia
+from pil_utils import BuildImage
+
+from meme_generator import add_meme
+from meme_generator.utils import (
+    Maker,
+    from_skia_image,
+    make_gif_or_combined_gif,
+    new_skia_surface,
+    skia_sampling_options,
+    to_skia_image,
+)
+
+
+def sphere_rotate(images: list[BuildImage], texts, args):
+    total_frames = 60
+
+    sksl_code = """
+        uniform shader image;
+        uniform float angle;
+        uniform float2 canvas_size;
+        uniform float2 image_size;
+
+        const float PI = 3.14159265359;
+
+        // Y轴旋转矩阵
+        mat3 rotate_y(float a) {
+            float s = sin(a);
+            float c = cos(a);
+            return mat3(
+                c, 0, s,
+                0, 1, 0,
+                -s, 0, c
+            );
+        }
+
+        // 光线与球体相交检测
+        // ro: 光线原点, rd: 光线方向, r: 球体半径
+        // 返回 vec2(近交点距离, 远交点距离), 如果不相交则都为-1.0
+        vec2 intersect_sphere(vec3 ro, vec3 rd, float r) {
+            float b = dot(ro, rd);
+            float c = dot(ro, ro) - r * r;
+            float h = b * b - c;
+            if (h < 0.0) {
+                return vec2(-1.0);
+            }
+            float sqrt_h = sqrt(h);
+            return vec2(-b - sqrt_h, -b + sqrt_h);
+        }
+
+        // 将球体表面的3D坐标点转换为2D纹理UV坐标 (等距柱状投影)
+        vec2 get_sphere_uv(vec3 p) {
+            p = normalize(p);
+            float u = 0.5 + atan(p.z, p.x) / (2.0 * PI);
+            float v = 0.5 + asin(p.y) / PI;
+            return vec2(u, v);
+        }
+
+        half4 main(vec2 coord) {
+            // 将屏幕像素坐标转换为标准化坐标
+            vec2 uv = (2.0 * coord - canvas_size.xy) / canvas_size.y;
+
+            // 设置相机 (光线追踪)
+            vec3 ro = vec3(0.0, 0.0, 3.5);
+            vec3 rd = normalize(vec3(uv, -2.0));
+
+            // 应用Y轴旋转
+            mat3 rot = rotate_y(angle);
+            ro = rot * ro;
+            rd = rot * rd;
+
+            float radius = 1.2;
+
+            // 寻找光线与完整球体的所有交点
+            vec2 t = intersect_sphere(ro, rd, radius);
+            float t_hit = -1.0;
+
+            // 测试近处的交点
+            if (t.x > 0.0) {
+                vec3 p1 = ro + rd * t.x;
+                if (p1.x >= 0.0) {
+                    t_hit = t.x;
+                }
+            }
+
+            // 如果近处交点无效，则测试远处的交点 (处理看到内壁的情况)
+            if (t_hit < 0.0 && t.y > 0.0) {
+                vec3 p2 = ro + rd * t.y;
+                if (p2.x >= 0.0) {
+                    t_hit = t.y;
+                }
+            }
+
+            // 如果找到了有效的交点，进行着色
+            if (t_hit > 0.0) {
+                vec3 pos = ro + rd * t_hit;
+                vec3 normal = normalize(pos);
+                float facing = dot(rd, normal);
+
+                vec2 tex_uv = get_sphere_uv(pos);
+                vec2 tex_coords = tex_uv * image_size;
+                half4 tex_color = image.eval(tex_coords);
+
+                if (facing < 0.0) {
+                    // 外表面: 直接使用纹理颜色
+                    return tex_color;
+                } else {
+                    // 内表面: 将纹理颜色变暗
+                    return tex_color * half4(0.7, 0.7, 0.7, 1.0);
+                }
+            }
+
+            return half4(0.0);
+        }
+    """
+    effect = skia.RuntimeEffect.MakeForShader(sksl_code)
+
+    def maker(i: int) -> Maker:
+        def make(imgs: list[BuildImage]):
+            img = imgs[0].convert("RGBA")
+            canvas_w, canvas_h = (300, 300)
+            surface = new_skia_surface((canvas_w, canvas_h))
+            canvas = surface.getCanvas()
+
+            angle = i / total_frames * math.pi * 2
+
+            values = []
+            for uniform in effect.uniforms():
+                if uniform.name == "angle":
+                    values.append(struct.pack("<f", angle))
+                elif uniform.name == "canvas_size":
+                    values.append(struct.pack("<f", canvas_w))
+                    values.append(struct.pack("<f", canvas_h))
+                elif uniform.name == "image_size":
+                    values.append(struct.pack("<f", img.width))
+                    values.append(struct.pack("<f", img.height))
+            uniforms = skia.Data.MakeWithCopy(b"".join(values))
+
+            skia_image = to_skia_image(img.image)
+            image_shader = skia_image.makeShader(skia_sampling_options())
+            shader = effect.makeShader(uniforms, image_shader, 1)
+
+            paint = skia.Paint()
+            paint.setShader(shader)
+            canvas.drawPaint(paint)
+            frame = BuildImage(from_skia_image(surface.makeImageSnapshot()))
+            return frame
+
+        return make
+
+    return make_gif_or_combined_gif(images, maker, total_frames, 0.04)
+
+
+add_meme(
+    "sphere_rotate",
+    sphere_rotate,
+    min_images=1,
+    max_images=1,
+    keywords=["球面旋转"],
+    date_created=datetime(2025, 7, 6),
+    date_modified=datetime(2025, 7, 6),
+)