fix: close image file handle after loading in LoadImage nodes

Fixes #3477

The LoadImage and LoadImageMask nodes opened image files but did not
close them after processing. This kept file handles open, preventing
other processes from accessing the files.

Added try/finally blocks to ensure img.close() is called after
processing completes.

nodes.py

@@ -1665,6 +1665,7 @@ class LoadImage:
 
         excluded_formats = ['MPO']
 
+        try:
             for i in ImageSequence.Iterator(img):
                 i = node_helpers.pillow(ImageOps.exif_transpose, i)
 
@@ -1698,6 +1699,8 @@ class LoadImage:
             else:
                 output_image = output_images[0]
                 output_mask = output_masks[0]
+        finally:
+            img.close()
 
         return (output_image, output_mask)
 
@@ -1734,6 +1737,7 @@ class LoadImageMask:
     def load_image(self, image, channel):
         image_path = folder_paths.get_annotated_filepath(image)
         i = node_helpers.pillow(Image.open, image_path)
+        try:
             i = node_helpers.pillow(ImageOps.exif_transpose, i)
             if i.getbands() != ("R", "G", "B", "A"):
                 if i.mode == 'I':
@@ -1748,6 +1752,8 @@ class LoadImageMask:
                     mask = 1. - mask
             else:
                 mask = torch.zeros((64,64), dtype=torch.float32, device="cpu")
+        finally:
+            i.close()
         return (mask.unsqueeze(0),)
 
     @classmethod

tests-unit/test_load_image_file_handle.py

@@ -0,0 +1,91 @@
+"""Tests for LoadImage and LoadImageMask file handle management.
+
+Relates to issue #3477: close image file after loading
+"""
+
+import pytest
+import tempfile
+import os
+from PIL import Image
+
+
+class TestImageFileHandleRelease:
+    """Test that image files are properly closed after loading."""
+
+    def test_file_handle_released_after_close(self):
+        """Verify file handle is released after calling close()."""
+        # Create a temporary test image
+        with tempfile.NamedTemporaryFile(suffix='.png', delete=False) as f:
+            temp_path = f.name
+
+        try:
+            # Create a test image
+            img = Image.new('RGB', (64, 64), color='red')
+            img.save(temp_path)
+
+            # Open and close the image
+            loaded_img = Image.open(temp_path)
+            loaded_img.load()  # Force load the image data
+            loaded_img.close()
+
+            # Try to delete the file - should succeed if handle is released
+            os.unlink(temp_path)
+            assert not os.path.exists(temp_path), "File should be deleted"
+        except Exception:
+            # Cleanup in case of failure
+            if os.path.exists(temp_path):
+                os.unlink(temp_path)
+            raise
+
+    def test_try_finally_pattern_releases_handle(self):
+        """Verify try/finally pattern properly releases file handle."""
+        with tempfile.NamedTemporaryFile(suffix='.png', delete=False) as f:
+            temp_path = f.name
+
+        try:
+            # Create a test image
+            img = Image.new('RGBA', (64, 64), color='blue')
+            img.save(temp_path)
+
+            # Simulate the pattern used in LoadImage
+            loaded_img = Image.open(temp_path)
+            try:
+                # Process the image
+                _ = loaded_img.convert("RGB")
+            finally:
+                loaded_img.close()
+
+            # Verify file can be accessed/deleted
+            os.unlink(temp_path)
+            assert not os.path.exists(temp_path)
+        except Exception:
+            if os.path.exists(temp_path):
+                os.unlink(temp_path)
+            raise
+
+    def test_image_data_preserved_after_close(self):
+        """Verify image data is preserved after closing the file."""
+        with tempfile.NamedTemporaryFile(suffix='.png', delete=False) as f:
+            temp_path = f.name
+
+        try:
+            # Create a test image with specific size
+            original_size = (128, 64)
+            img = Image.new('RGB', original_size, color='green')
+            img.save(temp_path)
+
+            # Load and process
+            loaded_img = Image.open(temp_path)
+            try:
+                loaded_img.load()
+                size = loaded_img.size
+                mode = loaded_img.mode
+            finally:
+                loaded_img.close()
+
+            # Data should still be valid after close
+            assert size == original_size
+            assert mode == 'RGB'
+        finally:
+            if os.path.exists(temp_path):
+                os.unlink(temp_path)