fix: image alpha error

app/services/image_processor.py

@@ -25,6 +25,38 @@ class ImageProcessor:
         """
         self.padding_ratio = padding_ratio or settings.image_padding_ratio
 
+    def _convert_to_bgr(self, pil_image: Image.Image) -> np.ndarray:
+        """Convert PIL Image to BGR numpy array, handling alpha channel.
+
+        Args:
+            pil_image: PIL Image object.
+
+        Returns:
+            Image as numpy array in BGR format.
+        """
+        # Handle RGBA images (PNG with transparency)
+        if pil_image.mode == "RGBA":
+            # Create white background and paste image on top
+            background = Image.new("RGB", pil_image.size, (255, 255, 255))
+            background.paste(pil_image, mask=pil_image.split()[3])  # Use alpha as mask
+            pil_image = background
+        elif pil_image.mode == "LA":
+            # Grayscale with alpha
+            background = Image.new("L", pil_image.size, 255)
+            background.paste(pil_image, mask=pil_image.split()[1])
+            pil_image = background.convert("RGB")
+        elif pil_image.mode == "P":
+            # Palette mode, may have transparency
+            pil_image = pil_image.convert("RGBA")
+            background = Image.new("RGB", pil_image.size, (255, 255, 255))
+            background.paste(pil_image, mask=pil_image.split()[3])
+            pil_image = background
+        elif pil_image.mode != "RGB":
+            # Convert other modes to RGB
+            pil_image = pil_image.convert("RGB")
+
+        return cv2.cvtColor(np.array(pil_image), cv2.COLOR_RGB2BGR)
+
     def load_image_from_url(self, url: str) -> np.ndarray:
         """Load image from URL.
 
@@ -40,8 +72,8 @@ class ImageProcessor:
         try:
             with urlopen(url, timeout=30) as response:
                 image_data = response.read()
-            image = Image.open(io.BytesIO(image_data))
-            return cv2.cvtColor(np.array(image), cv2.COLOR_RGB2BGR)
+            pil_image = Image.open(io.BytesIO(image_data))
+            return self._convert_to_bgr(pil_image)
         except Exception as e:
             raise ValueError(f"Failed to load image from URL: {e}") from e
 
@@ -63,8 +95,8 @@ class ImageProcessor:
                 base64_str = base64_str.split(",", 1)[1]
 
             image_data = base64.b64decode(base64_str)
-            image = Image.open(io.BytesIO(image_data))
-            return cv2.cvtColor(np.array(image), cv2.COLOR_RGB2BGR)
+            pil_image = Image.open(io.BytesIO(image_data))
+            return self._convert_to_bgr(pil_image)
         except Exception as e:
             raise ValueError(f"Failed to decode base64 image: {e}") from e