Enhance image preprocessing in app.py with improved background handling and color conversion

- Added hex_to_rgb function to convert hex color strings to RGB tuples.
- Updated preprocess_image to handle RGBA images, perform background removal, resize content, and apply a solid background color.
- Improved error handling for background removal failures, ensuring user feedback on model availability.

app.py

@@ -105,19 +105,37 @@ def add_background(image, bg_color=(255, 255, 255)):
     return Image.alpha_composite(background, image)
 
 
+def hex_to_rgb(hex_color: str) -> tuple[int, int, int]:
+    """Converts a hex color string to an RGB tuple."""
+    hex_color = hex_color.lstrip('#')
+    return tuple(int(hex_color[i:i+2], 16) for i in (0, 2, 4))
+
+
 def preprocess_image(image, background_choice, foreground_ratio, backgroud_color):
     """
-    input image is a pil image in RGBA, return RGB image
+    Preprocesses the input image by optionally removing the background, resizing,
+    and adding a new solid background.
+    Returns an RGB PIL Image.
     """
-    print(background_choice)
-    if background_choice == "Alpha as mask":
-        background = Image.new("RGBA", image.size, (0, 0, 0, 0))
-        image = Image.alpha_composite(background, image)
-    else:
+    if image.mode != 'RGBA':
+        image = image.convert('RGBA')
+
+    if background_choice == "Auto Remove background":
         image = remove_background(image)
         if image is None:
             raise gr.Error("Background removal failed. Please check the input image and ensure the model file exists and is valid.")
 
+    # Resize the content of the image
+    image = do_resize_content(image, foreground_ratio)
+    
+    # Add a solid background color
+    rgb_background = hex_to_rgb(backgroud_color)
+    image_with_bg = add_background(image, rgb_background)
+    
+    # Convert to RGB and return
+    return image_with_bg.convert("RGB")
+
+
 @spaces.GPU
 def gen_image(input_image, seed, scale, step):
     global pipeline, model, args