Merge pull request #227 from bgilbert/default-intent

Default to default rendering intent from slide ICC profile

Author: bgilbert

doc/index.rst

@@ -213,22 +213,21 @@ To include the profile in an image file when saving the image to disk::
     image.save(filename, icc_profile=image.info.get('icc_profile'))
 
 To perform color conversions using the profile, import it into
-:mod:`ImageCms <PIL.ImageCms>`.  For example, to convert an image in-place
-to a synthesized sRGB profile, using absolute colorimetric rendering::
+:mod:`ImageCms <PIL.ImageCms>`.  For example, to synthesize an sRGB profile
+and use it to transform an image for display, with the default rendering
+intent of the image's profile::
 
     from io import BytesIO
     from PIL import ImageCms
 
     fromProfile = ImageCms.getOpenProfile(BytesIO(image.info['icc_profile']))
     toProfile = ImageCms.createProfile('sRGB')
+    intent = ImageCms.getDefaultIntent(fromProfile)
     ImageCms.profileToProfile(
-        image, fromProfile, toProfile,
-        ImageCms.Intent.ABSOLUTE_COLORIMETRIC, 'RGBA', True, 0
+        image, fromProfile, toProfile, intent, 'RGBA', True, 0
     )
 
-Absolute colorimetric rendering `maximizes the comparability`_ of images
-produced by different scanners.  When converting Deep Zoom tiles, use
-``'RGB'`` instead of ``'RGBA'``.
+When converting Deep Zoom tiles, use ``'RGB'`` instead of ``'RGBA'``.
 
 All pyramid regions in a slide have the same profile, but each associated
 image can have its own profile.  As a convenience, the former is also
@@ -238,15 +237,13 @@ by building an :class:`~PIL.ImageCms.ImageCmsTransform` for the slide and
 reusing it for multiple slide regions::
 
     toProfile = ImageCms.createProfile('sRGB')
+    intent = ImageCms.getDefaultIntent(slide.color_profile)
     transform = ImageCms.buildTransform(
-        slide.color_profile, toProfile, 'RGBA', 'RGBA',
-        ImageCms.Intent.ABSOLUTE_COLORIMETRIC, 0
+        slide.color_profile, toProfile, 'RGBA', 'RGBA', intent, 0
     )
     # for each region image:
     ImageCms.applyTransform(image, transform, True)
 
-.. _maximizes the comparability: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4478790/
-
 
 Caching
 -------

examples/deepzoom/deepzoom_multiserver.py

@@ -73,7 +73,7 @@ def create_app(config=None, config_file=None):
         DEEPZOOM_OVERLAP=1,
         DEEPZOOM_LIMIT_BOUNDS=True,
         DEEPZOOM_TILE_QUALITY=75,
-        DEEPZOOM_COLOR_MODE='absolute-colorimetric',
+        DEEPZOOM_COLOR_MODE='default',
     )
     app.config.from_envvar('DEEPZOOM_MULTISERVER_SETTINGS', silent=True)
     if config_file is not None:
@@ -212,6 +212,8 @@ def _get_transform(self, image):
         elif mode == 'embed':
             # embed ICC profile in tiles
             return lambda img: None
+        elif mode == 'default':
+            intent = ImageCms.getDefaultIntent(image.color_profile)
         elif mode == 'absolute-colorimetric':
             intent = ImageCms.Intent.ABSOLUTE_COLORIMETRIC
         elif mode == 'relative-colorimetric':
@@ -276,18 +278,19 @@ def __init__(self, relpath):
         '--color-mode',
         dest='DEEPZOOM_COLOR_MODE',
         choices=[
+            'default',
             'absolute-colorimetric',
             'perceptual',
             'relative-colorimetric',
             'saturation',
             'embed',
             'ignore',
         ],
-        default='absolute-colorimetric',
+        default='default',
         help=(
-            'convert tiles to sRGB using specified rendering intent, or '
-            'embed original ICC profile, or ignore ICC profile (compat) '
-            '[absolute-colorimetric]'
+            'convert tiles to sRGB using default rendering intent of ICC '
+            'profile, or specified rendering intent; or embed original '
+            'ICC profile; or ignore ICC profile (compat) [default]'
         ),
     )
     parser.add_argument(

examples/deepzoom/deepzoom_server.py

@@ -73,7 +73,7 @@ def create_app(config=None, config_file=None):
         DEEPZOOM_OVERLAP=1,
         DEEPZOOM_LIMIT_BOUNDS=True,
         DEEPZOOM_TILE_QUALITY=75,
-        DEEPZOOM_COLOR_MODE='absolute-colorimetric',
+        DEEPZOOM_COLOR_MODE='default',
     )
     app.config.from_envvar('DEEPZOOM_TILER_SETTINGS', silent=True)
     if config_file is not None:
@@ -182,6 +182,8 @@ def get_transform(image, mode):
     elif mode == 'embed':
         # embed ICC profile in tiles
         return lambda img: None
+    elif mode == 'default':
+        intent = ImageCms.getDefaultIntent(image.color_profile)
     elif mode == 'absolute-colorimetric':
         intent = ImageCms.Intent.ABSOLUTE_COLORIMETRIC
     elif mode == 'relative-colorimetric':
@@ -224,18 +226,19 @@ def xfrm(img):
         '--color-mode',
         dest='DEEPZOOM_COLOR_MODE',
         choices=[
+            'default',
             'absolute-colorimetric',
             'perceptual',
             'relative-colorimetric',
             'saturation',
             'embed',
             'ignore',
         ],
-        default='absolute-colorimetric',
+        default='default',
         help=(
-            'convert tiles to sRGB using specified rendering intent, or '
-            'embed original ICC profile, or ignore ICC profile (compat) '
-            '[absolute-colorimetric]'
+            'convert tiles to sRGB using default rendering intent of ICC '
+            'profile, or specified rendering intent; or embed original '
+            'ICC profile; or ignore ICC profile (compat) [default]'
         ),
     )
     parser.add_argument(

examples/deepzoom/deepzoom_tile.py

@@ -125,6 +125,8 @@ def _get_transform(self, image):
         elif mode == 'embed':
             # embed ICC profile in tiles
             return lambda img: None
+        elif mode == 'default':
+            intent = ImageCms.getDefaultIntent(image.color_profile)
         elif mode == 'absolute-colorimetric':
             intent = ImageCms.Intent.ABSOLUTE_COLORIMETRIC
         elif mode == 'relative-colorimetric':
@@ -356,18 +358,19 @@ def _shutdown(self):
         '--color-mode',
         dest='color_mode',
         choices=[
+            'default',
             'absolute-colorimetric',
             'perceptual',
             'relative-colorimetric',
             'saturation',
             'embed',
             'ignore',
         ],
-        default='absolute-colorimetric',
+        default='default',
         help=(
-            'convert tiles to sRGB using specified rendering intent, or '
-            'embed original ICC profile, or ignore ICC profile (compat) '
-            '[absolute-colorimetric]'
+            'convert tiles to sRGB using default rendering intent of ICC '
+            'profile, or specified rendering intent; or embed original '
+            'ICC profile; or ignore ICC profile (compat) [default]'
         ),
     )
     parser.add_argument(