Fix BiRefNet issue (Comfy-Org#13966)

Author: yousef-rafat

comfy/bg_removal_model.py

@@ -44,7 +44,14 @@ def encode_image(self, image):
         comfy.model_management.load_model_gpu(self.patcher)
         H, W = image.shape[1], image.shape[2]
         pixel_values = comfy.clip_model.clip_preprocess(image.to(self.load_device), size=self.image_size, mean=self.image_mean, std=self.image_std, crop=False)
-        out = self.model(pixel_values=pixel_values)
+
+        if pixel_values.shape[0] > 1:
+            out = torch.cat([
+                self.model(pixel_values=pixel_values[i:i+1])
+                for i in range(pixel_values.shape[0])
+            ], dim=0)
+        else:
+            out = self.model(pixel_values=pixel_values)
         out = torch.nn.functional.interpolate(out, size=(H, W), mode="bicubic", antialias=False)
 
         mask = out.sigmoid().to(device=comfy.model_management.intermediate_device(), dtype=comfy.model_management.intermediate_dtype())