Update app.py

app.py

@@ -2,53 +2,53 @@ import gradio as gr
 from PIL import Image
 import numpy as np
 
-def white_alpha_overlay(mask_img, bg_img, invert_opacity=False):
-    if mask_img is None or bg_img is None:
+def white_from_brightness_overlay(fg_img, bg_img, invert_opacity=False):
+    if fg_img is None or bg_img is None:
         return None
 
-    # Convert and resize
-    mask = mask_img.convert("RGB")
+    # Resize fg to match bg
     bg = bg_img.convert("RGBA")
-    mask = mask.resize(bg.size)
+    fg = fg_img.convert("RGB").resize(bg.size)
 
-    # Convert brightness to alpha
-    mask_np = np.array(mask).astype(np.float32)
-    brightness = np.dot(mask_np[..., :3], [0.299, 0.587, 0.114])
+    # Convert to NumPy arrays
+    fg_np = np.array(fg).astype(np.float32)
+    bg_np = np.array(bg).astype(np.float32) / 255.0
+
+    # Calculate brightness
+    brightness = np.dot(fg_np[..., :3], [0.299, 0.587, 0.114])  # shape (H, W)
     if invert_opacity:
         brightness = 255 - brightness
-    alpha = brightness.clip(0, 255) / 255.0  # 0-1
+    alpha = (brightness / 255.0).clip(0, 1)  # shape (H, W)
 
-    # Create solid white RGBA with computed alpha
-    white = np.ones_like(mask_np) / 255.0  # RGB = 1.0 (white)
-    white_rgba = np.dstack((white, alpha))  # shape (H, W, 4)
-
-    # Background as float
-    bg_np = np.array(bg).astype(np.float32) / 255.0
+    # Create solid white with alpha from brightness
+    white = np.ones_like(fg_np)  # 255,255,255
+    white_alpha = np.dstack((white, alpha * 255)).astype(np.uint8)  # shape (H, W, 4)
+    white_img = Image.fromarray(white_alpha, mode="RGBA")
+    white_np = np.array(white_img).astype(np.float32) / 255.0
 
-    # Blend overlay on top of background
-    alpha_fg = white_rgba[..., 3:4]
-    alpha_bg = bg_np[..., 3:4]
-    out_alpha = alpha_fg + alpha_bg * (1 - alpha_fg)
-    out_rgb = (white_rgba[..., :3] * alpha_fg + bg_np[..., :3] * alpha_bg * (1 - alpha_fg)) / np.maximum(out_alpha, 1e-6)
+    # Blend white image over background using premultiplied alpha
+    fg_a = white_np[..., 3:4]
+    bg_a = bg_np[..., 3:4]
+    out_a = fg_a + bg_a * (1 - fg_a)
+    out_rgb = (white_np[..., :3] * fg_a + bg_np[..., :3] * bg_a * (1 - fg_a)) / np.maximum(out_a, 1e-6)
 
-    # Final image
-    out_img = np.dstack((out_rgb, out_alpha)).clip(0, 1) * 255
-    result = Image.fromarray(out_img.astype(np.uint8), mode="RGBA")
-    return result
+    # Final output
+    result = np.dstack((out_rgb, out_a)).clip(0, 1) * 255
+    return Image.fromarray(result.astype(np.uint8), mode="RGBA")
 
 # Gradio UI
 iface = gr.Interface(
-    fn=white_alpha_overlay,
+    fn=white_from_brightness_overlay,
     inputs=[
-        gr.Image(type="pil", label="Mask Image (Used for Brightness → Alpha)"),
-        gr.Image(type="pil", label="Background Image (With Alpha OK)"),
-        gr.Checkbox(label="Invert Brightness to Alpha", value=False)
+        gr.Image(type="pil", label="Input Image (Used for Brightness Only)"),
+        gr.Image(type="pil", label="Background Image (Can Have Transparency)"),
+        gr.Checkbox(label="Invert Brightness", value=False)
     ],
-    outputs=gr.Image(type="pil", label="White Overlay Composite"),
-    title="🕊️ Brightness-to-Alpha White Overlay",
+    outputs=gr.Image(type="pil", label="Final Output"),
+    title="✨ White Brightness-to-Alpha Overlay",
     description=(
-        "Converts the brightness of the top image into opacity, sets the image color to white, "
-        "and overlays it on a background. Works with full transparency."
+        "Uses the brightness of the input image to generate alpha. RGB is replaced with white. "
+        "Result is a smooth glowing white shape over your background, respecting transparency."
     )
 )