fix: 修复斜线刷子连线的空白问题

src/paint.rs

@@ -1,4 +1,4 @@
-use ::image::RgbaImage;
+use ::image::{ImageBuffer, ImageError, Rgba};
 use iced::Theme;
 use iced::padding;
 use iced::widget::container;
@@ -360,13 +360,14 @@ impl PaintApp {
                 let scale = 4;
                 let (width, height) = self.canvas.size();
                 let pixels = self.canvas.get_pixels_scale(4);
-                save_rgba_as_png(
+                save_rgba_to_png(
                     pixels,
                     (width * scale) as u32,
                     (height * scale) as u32,
                     "mspaint.png",
                 )
                 .unwrap();
+                println!("save png");
             }
             Message::RefreshImage => {
                 if self.dirty {
@@ -582,23 +583,16 @@ pub fn main() -> iced::Result {
         .run()
 }
 
-fn save_rgba_as_png(
-    pixels: Vec<u8>,
+fn save_rgba_to_png(
+    rgba_data: Vec<u8>,
     width: u32,
     height: u32,
     path: &str,
-) -> Result<(), Box<dyn std::error::Error>> {
-    // 验证像素数量是否匹配
-    if pixels.len() != (width * height * 4) as usize {
-        return Err("Pixel buffer size does not match width × height × 4".into());
-    }
+) -> Result<(), ImageError> {
+    // Each pixel is 4 bytes (R, G, B, A)
+    let img: ImageBuffer<Rgba<u8>, Vec<u8>> = ImageBuffer::from_raw(width, height, rgba_data)
+        .expect("Failed to create ImageBuffer: data size mismatch");
 
-    // 创建 RgbaImage
-    let img: RgbaImage = RgbaImage::from_vec(width, height, pixels)
-        .ok_or("Failed to create image from pixel data")?;
-
-    // 保存为 PNG（保留 Alpha 通道）
     img.save(path)?;
-
     Ok(())
 }