feat: 实现多边形填充

src/mscanvas.rs

@@ -1,4 +1,4 @@
-use iced::Point;
+use iced::{Color, Point};
 use rand::prelude::*;
 
 #[derive(Debug, Clone, Copy, PartialEq)]
@@ -35,6 +35,65 @@ impl MSColor {
         b: 255,
         a: 255,
     };
+
+    pub const RED: MSColor = MSColor {
+        r: 255,
+        g: 0,
+        b: 0,
+        a: 255,
+    };
+
+    pub const GREEN: MSColor = MSColor {
+        r: 0,
+        g: 255,
+        b: 0,
+        a: 255,
+    };
+
+    pub const BLUE: MSColor = MSColor {
+        r: 0,
+        g: 0,
+        b: 255,
+        a: 255,
+    };
+
+    pub fn into_color(self) -> Color {
+        Color::from_rgba8(
+            self.r,
+            self.g,
+            self.b,
+            (self.a / 255) as f32,
+        )
+    }
+}
+
+#[derive(Clone, Copy, PartialEq)]
+struct Edge {
+    y_max: i32,      // 边的最大 y（不包含）
+    x: f32,          // 当前扫描线 y 处的 x 值
+    dx_dy: f32,      // 1 / slope = Δx / Δy
+}
+
+impl Edge {
+    fn new(p1: Point, p2: Point) -> Option<Self> {
+        // 确保 p1.y <= p2.y
+        let (top, bottom) = if p1.y < p2.y { (p1, p2) } else { (p2, p1) };
+
+        // 忽略水平边（不会贡献交点）
+        if (top.y - bottom.y).abs() < f32::EPSILON {
+            return None;
+        }
+
+        let dx = (bottom.x - top.x);
+        let dy = (bottom.y - top.y);
+        let dx_dy = dx / dy;
+
+        Some(Edge {
+            y_max: bottom.y as i32,
+            x: top.x,
+            dx_dy,
+        })
+    }
 }
 
 pub struct Path2D {
@@ -61,7 +120,8 @@ pub struct MSCanvas {
     pixels_bak: Vec<u8>,
 
     /// 当前笔画颜色
-    color: MSColor,
+    foreground_color: MSColor,
+    background_color: MSColor,
 
     line_width: i32,
 
@@ -76,14 +136,19 @@ impl MSCanvas {
             height,
             pixels: vec![255; (width * height * 4) as usize],
             pixels_bak: Vec::new(),
-            color: MSColor::BLACK,
+            foreground_color: MSColor::BLACK,
+            background_color: MSColor::WHITE,
             line_width: 1,
             path2d: Path2D::new(),
         }
     }
 
-    pub fn set_color(&mut self, color: MSColor) {
+    pub fn set_foreground_color(&mut self, color: MSColor) {
-        self.color = color;
+        self.foreground_color = color;
+    }
+
+    pub fn set_background_color(&mut self, color: MSColor) {
+        self.background_color = color;
     }
 
     pub fn set_line_width(&mut self, line_width: i32) {
@@ -168,10 +233,10 @@ 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.color.r; // R
+        self.pixels[index] = self.foreground_color.r; // R
-        self.pixels[index + 1] = self.color.g; // G
+        self.pixels[index + 1] = self.foreground_color.g; // G
-        self.pixels[index + 2] = self.color.b; // B
+        self.pixels[index + 2] = self.foreground_color.b; // B
-        self.pixels[index + 3] = self.color.a; // A
+        self.pixels[index + 3] = self.foreground_color.a; // A
     }
 
     pub fn draw_pixel_color_at(&mut self, point: Point, color: MSColor) {
@@ -203,13 +268,17 @@ 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.color.r; // R
+        self.pixels[index] = self.foreground_color.r; // R
-        self.pixels[index + 1] = self.color.g; // G
+        self.pixels[index + 1] = self.foreground_color.g; // G
-        self.pixels[index + 2] = self.color.b; // B
+        self.pixels[index + 2] = self.foreground_color.b; // B
-        self.pixels[index + 3] = self.color.a; // A
+        self.pixels[index + 3] = self.foreground_color.a; // A
     }
 
     pub fn draw_pixel_row(&mut self, xs: i32, xe: i32, y: i32) {
+        self.draw_pixel_row_color(xs, xe, y, self.foreground_color);
+    }
+
+    pub fn draw_pixel_row_color(&mut self, xs: i32, xe: i32, y: i32, color: MSColor) {
         if y < 0 || y >= self.height {
             return;
         }
@@ -222,10 +291,10 @@ 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.color.r; // R
+            self.pixels[index] = color.r; // R
-            self.pixels[index + 1] = self.color.g; // G
+            self.pixels[index + 1] = color.g; // G
-            self.pixels[index + 2] = self.color.b; // B
+            self.pixels[index + 2] = color.b; // B
-            self.pixels[index + 3] = self.color.a; // A
+            self.pixels[index + 3] = color.a; // A
         }
     }
 
@@ -421,7 +490,7 @@ impl MSCanvas {
         let start_x = begin.x as i32;
         let start_y = begin.y as i32;
         let target_color = self.pixel_at(start_x, start_y);
-        if target_color == self.color {
+        if target_color == self.foreground_color {
             return (0, 0);
         }
 
@@ -465,7 +534,7 @@ impl MSCanvas {
         }
 
         let target_color = self.pixel_at(start_x, start_y);
-        if target_color == (self.color) {
+        if target_color == (self.foreground_color) {
             return (0, 0);
         }
 
@@ -609,10 +678,10 @@ impl MSCanvas {
         let max_sq = max_r * max_r;
 
         let color = MSColor::new(
-            (255 + self.color.r) / 2,
+            (255 + self.foreground_color.r) / 2,
-            self.color.g,
+            self.foreground_color.g,
-            self.color.b,
+            self.foreground_color.b,
-            self.color.a,
+            self.foreground_color.a,
         );
 
         let center_x = center.x as i32;
@@ -648,12 +717,20 @@ impl MSCanvas {
         }
     }
 
-    pub fn fill_rect(&mut self, x: i32, y: i32, width: i32, height: i32) {
+    fn fill_rect_color(&mut self, x: i32, y: i32, width: i32, height: i32, color: MSColor) {
         for yi in y..(y + height) {
-            self.draw_pixel_row(x, x + width, yi);
+            self.draw_pixel_row_color(x, x + width, yi, color);
         }
     }
 
+    fn fill_rect_foreground_color(&mut self, x: i32, y: i32, width: i32, height: i32) {
+        self.fill_rect_color(x, y, width, height, self.foreground_color);
+    }
+
+    pub fn fill_rect(&mut self, x: i32, y: i32, width: i32, height: i32) {
+        self.fill_rect_color(x, y, width, height, self.background_color)
+    }
+
     pub fn round_rect(&mut self, x: f32, y: f32, width: f32, height: f32, radius: f32) {
         if (width as i32) < 2 * self.line_width
             || (height as i32) < 2 * self.line_width
@@ -664,25 +741,25 @@ impl MSCanvas {
             return;
         }
 
-        self.fill_rect(
+        self.fill_rect_foreground_color(
             (x + radius) as i32,
             y as i32,
             (width - 2.0 * radius) as i32,
             self.line_width,
         );
-        self.fill_rect(
+        self.fill_rect_foreground_color(
             (x + radius) as i32,
             (y + height) as i32 - self.line_width,
             (width - 2.0 * radius) as i32,
             self.line_width,
         );
-        self.fill_rect(
+        self.fill_rect_foreground_color(
             x as i32,
             (y + radius) as i32,
             self.line_width,
             (height - 2.0 * radius) as i32,
         );
-        self.fill_rect(
+        self.fill_rect_foreground_color(
             (x + width) as i32 - self.line_width,
             (y + radius) as i32,
             self.line_width,
@@ -913,6 +990,68 @@ impl MSCanvas {
         }
     }
 
+    /// 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 {
+            return;
+        }
+
+        // 计算 y 范围
+        let min_y = points.iter().map(|p| p.y as i32).min().unwrap_or(0);
+        let max_y = points.iter().map(|p| p.y as i32).max().unwrap_or(0);
+
+        // 构建边表（Edge Table）：按 ymin 分组
+        let mut edge_table: Vec<Vec<Edge>> = vec![Vec::new(); (max_y - min_y + 1) as usize];
+
+        for i in 0..points.len() {
+            let p1 = points[i];
+            let p2 = points[(i + 1) % points.len()];
+            if let Some(edge) = Edge::new(p1, p2) {
+                let idx = (edge.x as i32).min(max_y).max(min_y); // 实际应使用 top.y
+                // 正确做法：使用 top.y 作为插入位置
+                let top_y = p1.y.min(p2.y) as i32;
+                if top_y >= min_y && top_y <= max_y {
+                    edge_table[(top_y - min_y) as usize].push(edge);
+                }
+            }
+        }
+
+        // 活动边表（Active Edge List），按 x 排序
+        let mut active_edges: Vec<Edge> = Vec::new();
+
+        // 从 min_y 到 max_y 扫描每一行
+        for y in min_y..=max_y {
+            let y_idx = (y - min_y) as usize;
+
+            // 1. 添加新边（y == ymin 的边）
+            if y_idx < edge_table.len() {
+                active_edges.append(&mut edge_table[y_idx]);
+            }
+
+            // 2. 移除 y >= y_max 的边
+            active_edges.retain(|e| y < e.y_max);
+
+            // 3. 按 x 排序
+            active_edges.sort_by(|a, b| a.x.partial_cmp(&b.x).unwrap_or(std::cmp::Ordering::Equal));
+
+            // 4. 成对填充像素
+            for i in (0..active_edges.len()).step_by(2) {
+                if i + 1 < active_edges.len() {
+                    let x_start = active_edges[i].x.ceil() as i32;
+                    let x_end = active_edges[i + 1].x.floor() as i32;
+                    for x in x_start..=x_end {
+                        self.draw_pixel_color_at(Point::new(x as f32, y as f32), self.background_color);
+                    }
+                }
+            }
+
+            // 5. 更新活动边的 x（为下一行准备）
+            for edge in &mut active_edges {
+                edge.x += edge.dx_dy;
+            }
+        }
+    }
+
     pub fn begin_path(&mut self) {
         self.path2d = Path2D::new();
     }
@@ -943,6 +1082,11 @@ impl MSCanvas {
             self.draw_line_with_circle_brush(points[i], points[i + 1]);
         }
     }
+
+    pub fn fill(&mut self) {
+        let points = self.path2d.points.clone();
+        self.fill_polygon(&points[..]);
+    }
 }
 
 fn point_muln(point: Point, t: f32) -> Point {