From d7f45712171edfe60bc43480b81a166b48252c8d Mon Sep 17 00:00:00 2001
From: yeqing <heopro@163.com>
Date: Sat, 28 Feb 2026 18:44:50 +0800
Subject: [PATCH] =?UTF-8?q?feat:=20=E5=AE=9E=E7=8E=B0=E6=A4=AD=E5=9C=86?=
 =?UTF-8?q?=E5=8A=9F=E8=83=BD?=
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---
 src/mscanvas.rs | 67 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/paint.rs    | 25 ++++++++++++++++++
 2 files changed, 92 insertions(+)

diff --git a/src/mscanvas.rs b/src/mscanvas.rs
index a2909c7..e2a9751 100644
--- a/src/mscanvas.rs
+++ b/src/mscanvas.rs
@@ -653,6 +653,73 @@ impl MSCanvas {
         self.bezier(points);
     }
 
+    pub fn ellipse(&mut self, center: Point, rx: f32, ry: f32) {
+        let mut x = 0.0;
+        let mut y = ry; // 初始时将y设置为半高
+
+        // 计算初始决策参数
+        let mut decision = ry * ry - rx * rx * ry + rx * rx / 4.0;
+
+        while ry * ry * x < rx * rx * y {
+            // 在每个阶段，根据对称性绘制四个方向上的点
+            self.draw_pixel_at(Point::new(center.x + x, center.y + y));
+            self.draw_pixel_at(Point::new(center.x - x, center.y + y));
+            self.draw_pixel_at(Point::new(center.x + x, center.y - y));
+            self.draw_pixel_at(Point::new(center.x - x, center.y - y));
+
+            if decision < 0.0 {
+                x += 1.0;
+                decision += 2.0 * ry * ry * x + ry * ry;
+            } else {
+                x += 1.0;
+                y -= 1.0;
+                decision += 2.0 * ry * ry * x - 2.0 * rx * rx * y + ry * ry;
+            }
+        }
+
+        decision =
+            ry * ry * (x + 0.5) * (x + 0.5) + rx * rx * (y - 1.0) * (y - 1.0) - rx * rx * ry * ry;
+
+        while y > 0.0 {
+            // 同样地，根据对称性绘制四个方向上的点
+            self.draw_pixel_at(Point::new(center.x + x, center.y + y));
+            self.draw_pixel_at(Point::new(center.x - x, center.y + y));
+            self.draw_pixel_at(Point::new(center.x + x, center.y - y));
+            self.draw_pixel_at(Point::new(center.x - x, center.y - y));
+
+            if decision > 0.0 {
+                y -= 1.0;
+                decision += rx * rx - 2.0 * rx * rx * y;
+            } else {
+                x += 1.0;
+                y -= 1.0;
+                decision += 2.0 * ry * ry * x - 2.0 * rx * rx * y + rx * rx;
+            }
+        }
+    }
+
+    pub fn 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.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.ellipse(center, rx, ry);
+        } else if ry < 0.0 {
+            ry = -ry;
+            let center = Point::new(p1.x + rx, p1.y - ry);
+            self.ellipse(center, rx, ry);
+        } else {
+            rx = -rx;
+            let center = Point::new(p1.x - rx, p1.y + ry);
+            self.ellipse(center, rx, ry);
+        }
+    }
+
     pub fn begin_path(&mut self) {
         self.path2d = Path2D::new();
     }
diff --git a/src/paint.rs b/src/paint.rs
index 085c83c..9dd4cab 100644
--- a/src/paint.rs
+++ b/src/paint.rs
@@ -447,6 +447,9 @@ impl PaintApp {
             Tool::Polygon => {
                 self.update_with_polygon(message);
             }
+            Tool::Ellipse => {
+                self.update_with_ellipse(message);
+            }
             _ => {}
         }
 
@@ -794,6 +797,28 @@ impl PaintApp {
         }
     }
 
+    pub fn update_with_ellipse(&mut self, message: Message) {
+        match message {
+            Message::MousePressed(pos) => {
+                self.is_drawing = true;
+                self.canvas.save_pixels();
+                self.begin_point = pos;
+            }
+            Message::MouseReleased(pos) => {
+                self.is_drawing = false;
+                self.begin_point = pos;
+            }
+            Message::MouseMoved(pos) => {
+                if self.is_drawing {
+                    self.canvas.restore_pixels();
+                    self.canvas.ellipse1(self.begin_point, pos);
+                    self.dirty = true;
+                }
+            }
+            _ => {}
+        }
+    }
+
     // endregion
 
     pub fn update_tool_states(&mut self, tool: Tool) {