Add ICC profile in ImageSlide.read_region() and get_thumbnail()

Have ImageSlide.read_region() and AbstractSlide.get_thumbnail() preserve
a reference to the underlying ICC profile, if any.

Add sRGB profile to boxes.png; retain the previous fixture as
boxes-no-icc.png.

Signed-off-by: Benjamin Gilbert <bgilbert@cs.cmu.edu>

Author: bgilbert

openslide/__init__.py

@@ -147,6 +147,8 @@ def get_thumbnail(self, size):
         # Image.Resampling added in Pillow 9.1.0
         # Image.LANCZOS removed in Pillow 10
         thumb.thumbnail(size, getattr(Image, 'Resampling', Image).LANCZOS)
+        if self._profile is not None:
+            thumb.info['icc_profile'] = self._profile
         return thumb
 
 
@@ -341,6 +343,7 @@ def __init__(self, file):
         else:
             self._close = True
             self._image = Image.open(file)
+        self._profile = self._image.info.get('icc_profile')
 
     def __repr__(self):
         return f'{self.__class__.__name__}({self._file_arg!r})'
@@ -430,6 +433,8 @@ def read_region(self, location, level, size):
             crop = self._image.crop(image_topleft + [d + 1 for d in image_bottomright])
             tile_offset = tuple(il - l for il, l in zip(image_topleft, location))
             tile.paste(crop, tile_offset)
+        if self._profile is not None:
+            tile.info['icc_profile'] = self._profile
         return tile
 
     def set_cache(self, cache):

tests/fixtures/boxes-no-icc.png

@@ -88,6 +88,14 @@ def test_metadata(self):
         self.assertEqual(self.osr.properties, {})
         self.assertEqual(self.osr.associated_images, {})
 
+    def test_color_profile(self):
+        self.assertEqual(
+            len(self.osr.read_region((0, 0), 0, (100, 100)).info['icc_profile']), 588
+        )
+        self.assertEqual(
+            len(self.osr.get_thumbnail((100, 100)).info['icc_profile']), 588
+        )
+
     def test_read_region(self):
         self.assertEqual(
             self.osr.read_region((-10, -10), 0, (400, 400)).size, (400, 400)
@@ -113,3 +121,13 @@ def test_thumbnail(self):
     def test_set_cache(self):
         self.osr.set_cache(OpenSlideCache(64 << 10))
         self.assertEqual(self.osr.read_region((0, 0), 0, (400, 400)).size, (400, 400))
+
+
+class TestNoIccImage(_SlideTest, unittest.TestCase):
+    FILENAME = 'boxes-no-icc.png'
+
+    def test_color_profile(self):
+        self.assertNotIn(
+            'icc_profile', self.osr.read_region((0, 0), 0, (100, 100)).info
+        )
+        self.assertNotIn('icc_profile', self.osr.get_thumbnail((100, 100)).info)

tests/fixtures/boxes.png

@@ -130,6 +130,9 @@ def test_color_profile(self):
         self.assertEqual(
             len(self.osr.read_region((0, 0), 0, (100, 100)).info['icc_profile']), 588
         )
+        self.assertEqual(
+            len(self.osr.get_thumbnail((100, 100)).info['icc_profile']), 588
+        )
 
     def test_read_region(self):
         self.assertEqual(
@@ -197,6 +200,7 @@ def test_color_profile(self):
             'icc_profile', self.osr.read_region((0, 0), 0, (100, 100)).info
         )
         self.assertNotIn('icc_profile', self.osr.associated_images['thumbnail'].info)
+        self.assertNotIn('icc_profile', self.osr.get_thumbnail((100, 100)).info)
 
 
 # Requires DICOM support in OpenSlide.  Use associated image ICC support as