feat: 实现椭圆填充功能

src/mscanvas.rs

@@ -261,7 +261,7 @@ impl MSCanvas {
         self.pixels[index + 3] = color.a; // A
     }
 
-    fn draw_pixel_at1(&mut self, x: i32, y: i32) {
+    fn draw_pixel_color_at1(&mut self, x: i32, y: i32, color: MSColor) {
         // 边界检查
         if x < 0 || x >= self.width || y < 0 || y >= self.height {
             return;
@@ -271,10 +271,14 @@ impl MSCanvas {
 
         // 写入 RGBA 数据
         // 注意：Color 的 r, g, b, a 是 0.0 - 1.0，需要转为 0 - 255
-        self.pixels[index] = self.foreground_color.r; // R
-        self.pixels[index + 1] = self.foreground_color.g; // G
-        self.pixels[index + 2] = self.foreground_color.b; // B
-        self.pixels[index + 3] = self.foreground_color.a; // A
+        self.pixels[index] = color.r; // R
+        self.pixels[index + 1] = color.g; // G
+        self.pixels[index + 2] = color.b; // B
+        self.pixels[index + 3] = color.a; // A
+    }
+
+    fn draw_pixel_at1(&mut self, x: i32, y: i32) {
+        self.draw_pixel_color_at1(x, y, self.foreground_color);
     }
 
     pub fn draw_pixel_row(&mut self, xs: i32, xe: i32, y: i32) {
@@ -525,7 +529,7 @@ impl MSCanvas {
         (iter_count, fill_count)
     }
 
-    pub fn fill_scanline(&mut self, begin: Point) -> (i32, i32) {
+    fn fill_scanline_with_color(&mut self, begin: Point, color: MSColor) {
         let start_x = begin.x as i32;
         let start_y = begin.y as i32;
         let width = self.width;
@@ -533,22 +537,18 @@ impl MSCanvas {
 
         // 边界检查
         if start_x < 0 || start_x >= width || start_y < 0 || start_y >= height {
-            return (0, 0);
+            return;
         }
 
         let target_color = self.pixel_at(start_x, start_y);
-        if target_color == (self.foreground_color) {
-            return (0, 0);
+        if target_color == color {
+            return;
         }
 
         // 栈中存储 (y, x1, x2)：表示第 y 行从 x1 到 x2（含）需要向上/下扫描
         let mut stack = vec![(start_y, start_x, start_x)];
-        let mut iter_count = 0;
-        let mut fill_count = 0;
 
         while let Some((y, mut lx, mut rx)) = stack.pop() {
-            iter_count += 1;
-
             // 向左扩展 lx
             while lx - 1 >= 0 && self.pixel_at(lx - 1, y) == target_color {
                 lx -= 1;
@@ -560,8 +560,7 @@ impl MSCanvas {
 
             // 填充当前行 [lx, rx]
             for x in lx..=rx {
-                self.draw_pixel_at1(x, y);
-                fill_count += 1;
+                self.draw_pixel_color_at1(x, y, color);
             }
 
             // 检查上一行 (y - 1)
@@ -598,8 +597,10 @@ impl MSCanvas {
                 }
             }
         }
+    }
 
-        (iter_count, fill_count)
+    pub fn fill_scanline(&mut self, begin: Point) {
+        self.fill_scanline_with_color(begin, self.foreground_color);
     }
 
     pub fn arc_1px(
@@ -1074,6 +1075,65 @@ impl MSCanvas {
         }
     }
 
+    /// 填充一个椭圆
+    /// - center: 椭圆中心
+    /// - rx: 水平半径（必须 >= 0）
+    /// - ry: 垂直半径（必须 >= 0）
+    pub fn fill_ellipse(&mut self, center: Point, rx: f32, ry: f32) {
+        if rx <= 0.0 || ry <= 0.0 {
+            return;
+        }
+
+        let rx = rx as f32;
+        let ry = ry as f32;
+
+        // 计算包围矩形（整数边界）
+        let min_x = (center.x as f32 - rx).ceil() as i32;
+        let max_x = (center.x as f32 + rx).floor() as i32;
+        let min_y = (center.y as f32 - ry).ceil() as i32;
+        let max_y = (center.y as f32 + ry).floor() as i32;
+
+        // 预计算常量：rx², ry², rx² * ry²
+        let rx2 = rx * rx;
+        let ry2 = ry * ry;
+        let rxy2 = rx2 * ry2; // 右边阈值
+
+        for y in min_y..=max_y {
+            for x in min_x..=max_x {
+                let dx = x as f32 - center.x as f32;
+                let dy = y as f32 - center.y as f32;
+
+                // 判断是否在椭圆内：dx²/ rx² + dy²/ ry² <= 1
+                // 等价于：dx² * ry² + dy² * rx² <= rx² * ry²
+                if dx * dx * ry2 + dy * dy * rx2 <= rxy2 {
+                    self.draw_pixel_color_at1(x, y, self.background_color);
+                }
+            }
+        }
+    }
+
+    pub fn fill_ellipse1(&mut self, p1: Point, p2: Point) {
+        let mut rx = (p2.x - p1.x) / 2.0;
+        let mut ry = (p2.y - p1.y) / 2.0;
+        if rx > 0.0 && ry > 0.0 {
+            let center = Point::new(p1.x + rx, p1.y + ry);
+            self.fill_ellipse(center, rx, ry);
+        } else if rx < 0.0 && ry < 0.0 {
+            rx = -rx;
+            ry = -ry;
+            let center = Point::new(p1.x - rx, p1.y - ry);
+            self.fill_ellipse(center, rx, ry);
+        } else if ry < 0.0 {
+            ry = -ry;
+            let center = Point::new(p1.x + rx, p1.y - ry);
+            self.fill_ellipse(center, rx, ry);
+        } else {
+            rx = -rx;
+            let center = Point::new(p1.x - rx, p1.y + ry);
+            self.fill_ellipse(center, rx, ry);
+        }
+    }
+
     /// 填充一个简单多边形（支持凹多边形）
     pub fn fill_polygon(&mut self, points: &[Point]) {
         if points.len() < 3 {