add difference blend mode

comfy_extras/nodes_post_processing.py

@@ -23,7 +23,7 @@ class Blend:
                     "max": 1.0,
                     "step": 0.01
                 }),
-                "blend_mode": (["normal", "multiply", "screen", "overlay", "soft_light"],),
+                "blend_mode": (["normal", "multiply", "screen", "overlay", "soft_light", "difference"],),
             },
         }
 
@@ -54,6 +54,8 @@ class Blend:
             return torch.where(img1 <= 0.5, 2 * img1 * img2, 1 - 2 * (1 - img1) * (1 - img2))
         elif mode == "soft_light":
             return torch.where(img2 <= 0.5, img1 - (1 - 2 * img2) * img1 * (1 - img1), img1 + (2 * img2 - 1) * (self.g(img1) - img1))
+        elif mode == "difference":
+            return img1 - img2
         else:
             raise ValueError(f"Unsupported blend mode: {mode}")