增强分离标记框的可视辨识度

为分离标记框增加两条绿色角到角交叉线。

新增 MARKER_LINE_WIDTH 常量统一配置标记线宽，并确保绘制结果裁剪在矩形内。

补充标记框像素级回归测试并同步更新自动分离专题文档。

apps/ai-game-creator-shell/src-tauri/src/ui_editor/commands/separation/marker.rs

@@ -3,6 +3,8 @@ use base64::Engine as _;
 use std::path::Path;
 use std::path::PathBuf;
 
+const MARKER_LINE_WIDTH: u32 = 2;
+
 pub async fn build_marked_image(
     source_url: String,
     nodes: Vec<SeparationNode>,
@@ -120,12 +122,144 @@ fn draw_frame(
         return;
     };
     let green = image::Rgba([0, 255, 0, 255]);
-    for xx in x0..=x1 {
-        image.put_pixel(xx, y0, green);
-        image.put_pixel(xx, y1, green);
-    }
-    for yy in y0..=y1 {
-        image.put_pixel(x0, yy, green);
-        image.put_pixel(x1, yy, green);
+    draw_line(
+        image,
+        (x0, y0),
+        (x1, y0),
+        green,
+        MARKER_LINE_WIDTH,
+        (x0, y0, x1, y1),
+    );
+    draw_line(
+        image,
+        (x0, y1),
+        (x1, y1),
+        green,
+        MARKER_LINE_WIDTH,
+        (x0, y0, x1, y1),
+    );
+    draw_line(
+        image,
+        (x0, y0),
+        (x0, y1),
+        green,
+        MARKER_LINE_WIDTH,
+        (x0, y0, x1, y1),
+    );
+    draw_line(
+        image,
+        (x1, y0),
+        (x1, y1),
+        green,
+        MARKER_LINE_WIDTH,
+        (x0, y0, x1, y1),
+    );
+    draw_line(
+        image,
+        (x0, y0),
+        (x1, y1),
+        green,
+        MARKER_LINE_WIDTH,
+        (x0, y0, x1, y1),
+    );
+    draw_line(
+        image,
+        (x1, y0),
+        (x0, y1),
+        green,
+        MARKER_LINE_WIDTH,
+        (x0, y0, x1, y1),
+    );
+}
+
+fn draw_line(
+    image: &mut image::RgbaImage,
+    start: (u32, u32),
+    end: (u32, u32),
+    color: image::Rgba<u8>,
+    line_width: u32,
+    bounds: (u32, u32, u32, u32),
+) {
+    let mut x = start.0 as i64;
+    let mut y = start.1 as i64;
+    let target_x = end.0 as i64;
+    let target_y = end.1 as i64;
+    let dx = (target_x - x).abs();
+    let sx = if x < target_x { 1 } else { -1 };
+    let dy = -(target_y - y).abs();
+    let sy = if y < target_y { 1 } else { -1 };
+    let mut error = dx + dy;
+
+    loop {
+        draw_brush(image, x, y, color, line_width, bounds);
+        if x == target_x && y == target_y {
+            break;
+        }
+        let twice_error = error * 2;
+        if twice_error >= dy {
+            error += dy;
+            x += sx;
+        }
+        if twice_error <= dx {
+            error += dx;
+            y += sy;
+        }
+    }
+}
+
+fn draw_brush(
+    image: &mut image::RgbaImage,
+    x: i64,
+    y: i64,
+    color: image::Rgba<u8>,
+    line_width: u32,
+    bounds: (u32, u32, u32, u32),
+) {
+    let (x0, y0, x1, y1) = bounds;
+    let line_width = line_width.max(1) as i64;
+    let before = (line_width - 1) / 2;
+    let after = line_width / 2;
+    let min_x = (x - before).max(x0 as i64);
+    let max_x = (x + after).min(x1 as i64);
+    let min_y = (y - before).max(y0 as i64);
+    let max_y = (y + after).min(y1 as i64);
+    for yy in min_y..=max_y {
+        for xx in min_x..=max_x {
+            image.put_pixel(xx as u32, yy as u32, color);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn draw_frame_adds_green_cross_corner_lines() {
+        let mut image = image::RgbaImage::from_pixel(8, 6, image::Rgba([1, 2, 3, 255]));
+        draw_frame(&mut image, 1, 1, 5, 3, 8, 6);
+        let green = image::Rgba([0, 255, 0, 255]);
+
+        for &(x, y) in &[(1, 1), (5, 1), (1, 3), (5, 3), (3, 2)] {
+            assert_eq!(*image.get_pixel(x, y), green, "pixel ({x}, {y})");
+        }
+        assert_eq!(*image.get_pixel(3, 1), green);
+        assert_eq!(*image.get_pixel(3, 3), green);
+        assert_eq!(*image.get_pixel(2, 2), green);
+        assert_eq!(*image.get_pixel(4, 2), green);
+        assert_eq!(*image.get_pixel(0, 0), image::Rgba([1, 2, 3, 255]));
+    }
+
+    #[test]
+    fn draw_frame_keeps_cross_inside_clipped_rect() {
+        let mut image = image::RgbaImage::from_pixel(4, 4, image::Rgba([1, 2, 3, 255]));
+        draw_frame(&mut image, 2, 2, 4, 4, 4, 4);
+        let green = image::Rgba([0, 255, 0, 255]);
+        for y in 2..4 {
+            for x in 2..4 {
+                assert_eq!(*image.get_pixel(x, y), green);
+            }
+        }
+        assert_eq!(*image.get_pixel(1, 1), image::Rgba([1, 2, 3, 255]));
     }
 }

apps/ai-game-creator-shell/src-tauri/src/ui_editor/commands/separation/prompt.rs

@@ -5,8 +5,10 @@ const SHARED_SEPARATION_REQ: &str = r#"
     MUST hard edges; preserve no glow/blur beyond the exact visible shape.
     NEVER keep its parent's background with it.
 
-    UI elements that needs to extract has been marked with GREEN line frames (only for mark purpose, NEVER wrap a frame in your extraction).
+    UI elements that needs to extract has been marked with GREEN line frames box with crossline inside. (only for mark purpose, NEVER wrap a frame in your extraction).
     On some UI elements, there is some PURPLE filled area, they were removed UI elements, reconstruct the background under where they were.
+
+    MUST extract exactly these marked UI elements area.
 "#;
 pub(super) fn gen_extract_prompt(separation_notes: Vec<SeparationNote>) -> String {
     let extract_system_prompt = format!(

docs/technical/【技术方案】UI编辑器自动分离工作流-2026-09-08.md

@@ -29,7 +29,7 @@
 
 ## 图片编辑与视觉绑定
 
-- image-edit 使用源 UI design 图片及由 Rust 生成的绿色标记/紫色重建输入。处理父节点时，紫色填充其 children 的矩形区域（包括已 problematic 的 children），再在父节点自身外围绘制绿色框；绿色框覆盖在紫色之上。叶节点只绘制绿色框，不填充自身。
+- image-edit 使用源 UI design 图片及由 Rust 生成的绿色标记/紫色重建输入。处理父节点时，紫色填充其 children 的矩形区域（包括已 problematic 的 children），再在父节点自身外围绘制绿色框和角到角的绿色交叉线；绿色标记覆盖在紫色之上。叶节点只绘制绿色框和角到角的绿色交叉线，不填充自身。
 - 请求尺寸始终使用源 UI design 尺寸；Raw GPT Image 2 API 保证返回相同尺寸，客户端不额外做尺寸拒绝检查。
 - 标记图构建、处理图解码/写入和 cut 裁切属于本地 CPU/文件操作，放入独立的
   `spawn_blocking` 任务；image-edit 与 visual binding 网络请求仍运行在 async future 中。