Use 16-bit mode, not coloration, to check for RCM images

Author: brianhelba

isic/ingest/models/accession.py

@@ -527,8 +527,7 @@ def generate_blob(self):  # noqa: PLR0915
                 self.height = img.height
                 self.width = img.width
 
-                is_rcm = not self.is_color(img)
-
+                is_rcm = img.mode.startswith("I;16")
                 if is_rcm:
                     self.is_cog = self.meets_cog_threshold(img)
                     if self.is_cog:
@@ -542,6 +541,8 @@ def generate_blob(self):  # noqa: PLR0915
                 else:
                     if self.meets_cog_threshold(img):
                         raise InvalidBlobError("Blob is too large to be stored.")  # noqa: TRY301
+                    if not img.mode.startswith("RGB"):
+                        raise InvalidBlobError("Blob has non-RGB mode.")  # noqa: TRY301
                     self.is_cog = False
                     converter = self._convert_blob_to_rgb
                     converted_blob_type = "image/jpeg"
@@ -843,10 +844,6 @@ def metadata_keys():
             field.name for field in Accession._meta.fields if hasattr(AccessionMetadata, field.name)
         ]
 
-    @staticmethod
-    def is_color(img: PIL.Image.Image) -> bool:
-        return img.mode in {"RGB", "RGBA"}
-
     @staticmethod
     def meets_cog_threshold(img: PIL.Image.Image) -> bool:
         return img.height * img.width > IMAGE_COG_THRESHOLD