Add fallback output polarity control

app.py

@@ -28,6 +28,8 @@ ADAPTER_SUBFOLDER = os.getenv("ADAPTER_SUBFOLDER", "")
 
 MODEL_MODE = os.getenv("MODEL_MODE", "cpu-fallback").strip().lower()
 CPU_FALLBACK_MODEL_ID = os.getenv("CPU_FALLBACK_MODEL_ID", "DaMsTaR/Detecto-DeepFake_Image_Detector")
+DEFAULT_INVERT_FALLBACK = CPU_FALLBACK_MODEL_ID.lower() == "damstar/detecto-deepfake_image_detector"
+INVERT_FALLBACK_OUTPUT = os.getenv("INVERT_FALLBACK_OUTPUT", str(DEFAULT_INVERT_FALLBACK)).strip().lower() == "true"
 
 TMOS_PROMPT = "USER: <image>\nIs this video real or produced by AI?\nASSISTANT:"
 TARGET_IMAGE_SIZE = 336
@@ -322,6 +324,9 @@ def score_fallback_logits(logits: torch.Tensor, id2label: dict) -> tuple[float,
     else:
         prob_fake = float(probs.max().item()) if len(probs) == 1 else float(probs[1].item()) if len(probs) > 1 else 0.5
 
+    if INVERT_FALLBACK_OUTPUT:
+        prob_fake = 1.0 - prob_fake
+
     label = "Fake" if prob_fake >= THRESHOLD else "Real"
     return prob_fake, label
 
@@ -384,7 +389,7 @@ with gr.Blocks(title="TMOS Deepfake Detector", theme=gr.themes.Soft()) as demo:
     demo_description = (
         "TMOS mode (GPU required) enabled.\n\n"
         if MODEL_MODE == "tmos"
-        else f"CPU fallback mode using {CPU_FALLBACK_MODEL_ID}.\n\n"
+        else f"CPU fallback mode using {CPU_FALLBACK_MODEL_ID} (invert_output={INVERT_FALLBACK_OUTPUT}).\n\n"
     )
     gr.Markdown(
         "# TMOS Deepfake Detector\n"