diff --git a/src/paint.rs b/src/paint.rs
index 387c976..f8b34bc 100644
--- a/src/paint.rs
+++ b/src/paint.rs
@@ -4,7 +4,8 @@ use iced::padding;
 use iced::widget::container;
 use iced::widget::{Column, button, column, image, pick_list, row, text};
 use iced::{Border, Color, Element, Length, Point, Renderer, Task};
-use iced_core::color;
+use iced::{Subscription, color, event, mouse};
+use std::thread;
 
 use crate::image_button::image_button;
 use crate::mouse_area::mouse_area;
@@ -54,7 +55,7 @@ enum Message {
 
     Clear,
     SavePNG,
-    // 内部消息：请求刷新图像
+    /// 内部消息：请求刷新图像
     RefreshImage,
 
     ClickTool(Tool),
@@ -63,6 +64,9 @@ enum Message {
     Decrement(ConfigOption),
 
     BrushSelected(BrushKind),
+
+    /// 全局鼠标释放
+    WindowMouseRelease,
 }
 
 #[derive(Clone, Copy, Debug)]
@@ -200,7 +204,7 @@ struct PaintApp {
 }
 
 impl PaintApp {
-    // region iced application (new view update)
+    // region iced application
 
     pub fn new() -> Self {
         let mut canvas = MSCanvas::new(WIDTH as i32, HEIGHT as i32);
@@ -357,17 +361,10 @@ impl PaintApp {
                 self.dirty = true;
             }
             Message::SavePNG => {
-                let scale = 4;
                 let (width, height) = self.canvas.size();
-                let pixels = self.canvas.get_pixels_scale(4);
-                save_rgba_to_png(
-                    pixels,
-                    (width * scale) as u32,
-                    (height * scale) as u32,
-                    "mspaint.png",
-                )
-                .unwrap();
-                println!("save png");
+                let pixels = self.canvas.get_pixels();
+                let path = "mspaint.png";
+                save_pixels_async(pixels, width as u32, height as u32, 4, path.to_string());
             }
             Message::RefreshImage => {
                 if self.dirty {
@@ -393,6 +390,10 @@ impl PaintApp {
             Message::BrushSelected(kind) => {
                 self.brush_selected = Some(kind);
             }
+            Message::WindowMouseRelease => {
+                // 处理鼠标在 canvas_area 外面释放
+                self.is_drawing = false;
+            }
             _ => {}
         }
 
@@ -407,6 +408,16 @@ impl PaintApp {
         Task::none()
     }
 
+    pub fn subscription(&self) -> Subscription<Message> {
+        event::listen().filter_map(|event| match event {
+            // 只关心鼠标释放事件
+            iced::Event::Mouse(mouse::Event::ButtonReleased(mouse::Button::Left)) => {
+                Some(Message::WindowMouseRelease)
+            }
+            _ => None,
+        })
+    }
+
     // endregion
 
     // region tool update
@@ -580,6 +591,7 @@ impl PaintApp {
 pub fn main() -> iced::Result {
     iced::application(PaintApp::new, PaintApp::update, PaintApp::view)
         .theme(Theme::Dark)
+        .subscription(PaintApp::subscription)
         .run()
 }
 
@@ -596,3 +608,52 @@ fn save_rgba_to_png(
     img.save(path)?;
     Ok(())
 }
+
+fn scale_pixels(pixels: Vec<u8>, width: u32, height: u32, scale: u32) -> Vec<u8> {
+    if scale <= 1 {
+        return pixels;
+    }
+    let dst_width = width * scale;
+    let dst_height = height * scale;
+    let mut dst = vec![0; (dst_width * dst_height * 4) as usize]; // RGBA
+
+    for y in 0..height {
+        for x in 0..width {
+            // 源像素索引
+            let src_idx = ((y * width + x) * 4) as usize;
+
+            // 源像素颜色
+            let r = pixels[src_idx];
+            let g = pixels[src_idx + 1];
+            let b = pixels[src_idx + 2];
+            let a = pixels[src_idx + 3];
+
+            // 在目标图像中填充 scale×scale 区域
+            for dy in 0..scale {
+                for dx in 0..scale {
+                    let dst_x = x * scale + dx;
+                    let dst_y = y * scale + dy;
+                    let dst_idx = ((dst_y * dst_width + dst_x) * 4) as usize;
+
+                    dst[dst_idx] = r;
+                    dst[dst_idx + 1] = g;
+                    dst[dst_idx + 2] = b;
+                    dst[dst_idx + 3] = a;
+                }
+            }
+        }
+    }
+
+    dst
+}
+
+fn save_pixels_async(pixels: Vec<u8>, width: u32, height: u32, scale: u32, path: String) {
+    // 用 Arc 共享数据（或直接 move 进去）
+    thread::spawn(move || {
+        let pixels = scale_pixels(pixels, width, height, scale);
+        match save_rgba_to_png(pixels, width, height, &path) {
+            Ok(()) => println!("✅ Image saved to {}", path),
+            Err(e) => eprintln!("❌ Failed to save image: {}", e),
+        }
+    });
+}