feat: 选择功能支持透明模式

src/mscanvas.rs

@@ -270,13 +270,21 @@ impl MSCanvas {
         }
     }
 
-    pub fn select_rect(&self, x: i32, y: i32, w: i32, h: i32) -> RectSelection {
+    pub fn select_rect(&self, x: i32, y: i32, w: i32, h: i32, is_transparent_white: bool) -> RectSelection {
         let mut result = vec![255; (w * h * 4) as usize];
 
         let mut index = 0;
+        let default_color = if is_transparent_white {
+            MSColor::ZERO
+        } else {
+            MSColor::WHITE
+        };
         for yi in y..(y + h) {
             for xi in x..(x + w) {
-                let color = self.pixel_at(xi, yi).unwrap_or(MSColor::WHITE);
+                let mut color = self.pixel_at(xi, yi).unwrap_or(default_color);
+                if is_transparent_white && color == MSColor::WHITE {
+                    color = MSColor::ZERO;
+                }
                 result[index] = color.r;
                 result[index + 1] = color.g;
                 result[index + 2] = color.b;