diff --git a/src/mscanvas.rs b/src/mscanvas.rs
index aa6a77a..f6121c9 100644
--- a/src/mscanvas.rs
+++ b/src/mscanvas.rs
@@ -293,24 +293,48 @@ impl MSCanvas {
         let width = canvas.width.min(self.width) as usize;
         let height = canvas.height.min(self.height) as usize;
 
-        // 预计算步长，避免重复计算
         let src_stride = self.width as usize * 4;
-        let dst_stride = width * 4;
+        let dst_stride = canvas.width as usize * 4; // ⚠️ Bug fix: use canvas.width, not `width`
 
         for y in 0..height {
-            let src_base = y * src_stride;
-            let dst_base = y * dst_stride;
+            let src_row = &self.pixels[y * src_stride..y * src_stride + width * 4];
+            let dst_row = &mut pixels[y * dst_stride..y * dst_stride + width * 4];
 
-            // 使用显式循环，可能被编译器自动向量化
-            for x in 0..width {
-                let src_idx = src_base + x * 4;
-                let dst_idx = dst_base + x * 4;
+            // Process 4 pixels at a time (16 bytes) for better auto-vectorization
+            let chunks = width / 4;
+            let remainder = width % 4;
 
-                // 只在非透明时复制
-                if self.pixels[src_idx + 3] != 0 {
-                    // 一次复制4个字节（可能被优化为单个u32操作）
-                    pixels[dst_idx..dst_idx + 4]
-                        .copy_from_slice(&self.pixels[src_idx..src_idx + 4]);
+            for chunk in 0..chunks {
+                let base = chunk * 16;
+                // Check alpha bytes for 4 pixels at once
+                let a0 = src_row[base + 3];
+                let a1 = src_row[base + 7];
+                let a2 = src_row[base + 11];
+                let a3 = src_row[base + 15];
+
+                if a0 | a1 | a2 | a3 != 0 {
+                    // At least one pixel is non-transparent
+                    if a0 != 0 && a1 != 0 && a2 != 0 && a3 != 0 {
+                        // All 4 pixels are non-transparent — bulk copy 16 bytes
+                        dst_row[base..base + 16].copy_from_slice(&src_row[base..base + 16]);
+                    } else {
+                        // Mixed — copy individually
+                        for i in 0..4 {
+                            let off = base + i * 4;
+                            if src_row[off + 3] != 0 {
+                                dst_row[off..off + 4].copy_from_slice(&src_row[off..off + 4]);
+                            }
+                        }
+                    }
+                }
+                // else: all 4 transparent — skip entirely
+            }
+
+            // Handle remaining pixels
+            for x in (chunks * 4)..width {
+                let off = x * 4;
+                if src_row[off + 3] != 0 {
+                    dst_row[off..off + 4].copy_from_slice(&src_row[off..off + 4]);
                 }
             }
         }
diff --git a/src/paint.rs b/src/paint.rs
index b984566..b1619bf 100644
--- a/src/paint.rs
+++ b/src/paint.rs
@@ -1,5 +1,3 @@
-use std::thread;
-
 use ::image::{ImageBuffer, ImageError, Rgba};
 use iced::Theme;
 use iced::padding;
@@ -9,6 +7,8 @@ use iced::widget::container;
 use iced::widget::{Column, button, column, image, pick_list, row, text};
 use iced::{Border, Element, Length, Point, Renderer, Subscription, Task};
 use iced::{color, event, mouse};
+use std::thread;
+// use std::time::Duration;
 
 use crate::color_box::{ColorSelectionBox, CurrentColorBox};
 use crate::image_button::image_button;
@@ -596,6 +596,8 @@ impl PaintApp {
     }
 
     pub fn update(&mut self, message: Message) -> Task<Message> {
+        // let now = Instant::now();
+
         match self.tool_selected {
             Tool::Select => {
                 self.update_with_select(message);
@@ -718,6 +720,11 @@ impl PaintApp {
             return Task::perform(async { Message::RefreshImage }, |msg| msg);
         }
 
+        // let elapsed = now.elapsed();
+        // if elapsed.gt(&Duration::from_millis(10)) {
+        //     println!("update used: {:?}", elapsed);
+        // }
+
         Task::none()
     }
 
@@ -1393,13 +1400,17 @@ impl PaintApp {
 
     /// 将原始字节转换为 Iced 的图像句柄
     fn update_image_handle(&mut self) {
+        // let now = Instant::now();
         // 克隆数据以避免所有权问题，或者使用 Arc 如果数据量大
         // 这里为了简单直接 clone，对于 800x600 (约 2MB) 来说很快
         // let data = self.canvas.get_pixels();
         let data = self.view_canvas.overlay_pixels(&self.canvas);
+        // println!("overlay_pixels used: {:?}", now.elapsed());
         let (width, height) = self.canvas.size();
 
         self.image_handle = image::Handle::from_rgba(width as u32, height as u32, data);
+
+        // println!("update_image_handle used: {:?}", now.elapsed());
     }
 }