Change back to the compressed version of normal_map.tif as decompress…

…ed it lost the RGBX colour mode. Add RGBX support - convert to RGBA. Document RGBX support

docs/jp2_colour_management.rst

@@ -58,6 +58,11 @@ The ``kdu_compress`` :ref:`command options <kdu_compress-options>` we use do not
 
 As very few of our input images have an alpha channel, and we have not encountered failing cases in live data (as opposed to constructed test data), this is not a priority for us. We just make sure to check RGBA JP2 conversions are lossless, so we will catch any future failing cases.
 
+RGBX colour mode
+~~~~~~~~~~~~~~~~~~
+
+I could not find a simple way to convert an RGBX TIFF to an RGBX JP2, though it's possible more work would produce one. In our particular use case it's always clear whether the image should be interpreted as RGBA or RGBX, so we convert RGBX images to RGBA, preserving all of the pixel data but not the colour mode. The program logs a warning when converting RGBX files because of this.
+
 Colour profiles / modes not supported by JP2
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

image_processing/derivative_files_generator.py

@@ -216,6 +216,11 @@ def generate_jp2_from_tiff(self, tiff_file, jp2_filepath):
             if tiff_pil.mode == 'RGBA':
                 if kakadu.ALPHA_OPTION not in kakadu_options:
                     kakadu_options += [kakadu.ALPHA_OPTION]
+            elif tiff_pil.mode == 'RGBX':
+                self.log.warning('Input tiff has colour mode RGBX. It will be converted to RGBA')
+                if kakadu.ALPHA_OPTION not in kakadu_options:
+                    kakadu_options += [kakadu.ALPHA_OPTION]
+
 
         self.kakadu.kdu_compress(tiff_file, jp2_filepath, kakadu_options=kakadu_options)
         self.log.debug('Lossless jp2 file {0} generated'.format(jp2_filepath))

image_processing/validation.py

@@ -14,7 +14,7 @@
 GREYSCALE = 'L'
 BITONAL = '1'
 MONOTONE_COLOUR_MODES = [GREYSCALE, BITONAL]
-ACCEPTED_COLOUR_MODES = ['RGB', 'RGBA', 'RGBX', 'I;16', GREYSCALE, BITONAL]  # todo: are there any other modes we may have to consider? Need to add test for RGBX image
+ACCEPTED_COLOUR_MODES = ['RGB', 'RGBA', 'RGBX', 'I;16', GREYSCALE, BITONAL]
 
 
 def validate_jp2(image_file, output_file=None):
@@ -154,6 +154,8 @@ def check_colour_profiles_match(source_filepath, converted_filepath):
             if source_image.mode != converted_image.mode:
                 if source_image.mode == BITONAL and converted_image.mode == GREYSCALE:
                     logger.info('Converted image is greyscale, not bitonal. This is expected')
+                elif source_image.mode == 'RGBX' and converted_image.mode == 'RGBA':
+                    logger.info('Converted image in RGBA space, but was converted from RGBX. This is expected.')
                 else:
                     raise exceptions.ValidationError(
                         f'Converted file {converted_filepath} has different colour mode ({converted_image.mode}) from {source_filepath} ({source_image.mode})'

tests/test_derivatives_generator.py

@@ -226,7 +226,7 @@ def test_creates_correct_files_from_jpg(self):
             assert image_files_match(jp2_file, filepaths.LOSSLESS_JP2_FROM_STANDARD_JPG_XMP)
             assert xmp_files_match(embedded_metadata_file, filepaths.STANDARD_JPG_XMP)
 
-    def test_converts_depthmap_tif_to_jpeg2000_losslessly(self):
+    def test_converts_i_16_tif_to_jpeg2000_losslessly(self):
         """
         Check transformations of 16 bit depthmap images do not lose data
         :return:
@@ -238,15 +238,15 @@ def test_converts_depthmap_tif_to_jpeg2000_losslessly(self):
             assert os.path.isfile(output_file)
             generator.check_conversion_was_lossless(filepaths.DEPTHMAP_TIF, output_file)
 
-    def test_converts_normalmap_tif_to_jpeg2000_losslessly(self):
+    def test_converts_rgbx_tif_to_jpeg2000_losslessly(self):
         """
-        Check transformations of RGBA normal map images do not lose data
+        Check transformations of RGBX normal map images do not lose data
         :return:
         """
         with temporary_folder() as output_folder:
             generator = get_derivatives_generator()
             output_file = os.path.join(output_folder, 'output.jp2')
-            # note that this method has specific handling for files with alpha channels that the direct converter method does not
+            # note that this method has specific handling for files with four channels that the direct converter method does not
             generator.generate_jp2_from_tiff(filepaths.NORMALMAP_TIF, output_file)
             assert os.path.isfile(output_file)
             generator.check_conversion_was_lossless(filepaths.NORMALMAP_TIF, output_file)

tests/test_utils/filepaths.py

@@ -2,8 +2,6 @@
 
 # adobe rgb 1998 8 bit tiff file (our most common input format) + expected derivatives
 STANDARD_TIF = 'tests/data/standard_adobe.tif'
-DEPTHMAP_TIF = 'tests/data/depth_map.tif'  # 16 bit (I;16) archiox image
-NORMALMAP_TIF = 'tests/data/normal_map.tif'  # RGBA archiox image
 STANDARD_TIF_SINGLE_LAYER = 'tests/data/standard_adobe_tif_single_layer.tif'  # same tif but without thumbnail
 LOSSY_JP2_FROM_STANDARD_TIF = 'tests/data/standard_adobe_tif_lossy.jp2'
 LOSSLESS_JP2_FROM_STANDARD_TIF_XMP = 'tests/data/standard_adobe_tif_xmp.jp2'
@@ -51,6 +49,10 @@
 
 NO_PROFILE_TIF = 'tests/data/no_profile.tif'
 
+# tifs from our archiox project, which can have unusual colour modes
+DEPTHMAP_TIF = 'tests/data/depth_map.tif'  # 16 bit (I;16) archiox image
+NORMALMAP_TIF = 'tests/data/normal_map.tif'  # RGBX archiox image (compressed, as decompression with Image Magick converts it to RGBA)
+
 # just truncated files
 INVALID_JP2 = 'tests/data/invalid.jp2'
 INVALID_TIF = 'tests/data/invalid.tif'