added fits compatibility for live viewer (#1996)

docs/release_notes/next/feature-1996-fits-compatibility

@@ -0,0 +1 @@
+#1996 : Added .fits file compatibility for Live Viewer

mantidimaging/gui/windows/live_viewer/model.py

@@ -259,9 +259,8 @@ def _is_image_file(file_name: str) -> bool:
         :param file_name: name of file
         :return: True if file is an image file
         """
-        image_extensions = ['.tif', '.tiff']
-        file_names = any(file_name.lower().endswith(ext) for ext in image_extensions)
-        return file_names
+        image_extensions = ('tif', 'tiff', 'fits')
+        return file_name.rpartition(".")[2].lower() in image_extensions
 
     def remove_path(self):
         """

mantidimaging/gui/windows/live_viewer/presenter.py

@@ -8,6 +8,7 @@
 
 from imagecodecs._deflate import DeflateError
 from tifffile import tifffile, TiffFileError
+from astropy.io import fits
 
 from mantidimaging.gui.mvp_base import BasePresenter
 from mantidimaging.gui.windows.live_viewer.model import LiveViewerWindowModel, Image_Data
@@ -77,8 +78,12 @@ def select_image(self, index: int) -> None:
 
     def load_and_display_image(self, image_path: Path):
         try:
-            with tifffile.TiffFile(image_path) as tif:
-                image_data = tif.asarray()
+            if image_path.suffix.lower() in [".tif", ".tiff"]:
+                with tifffile.TiffFile(image_path) as tif:
+                    image_data = tif.asarray()
+            elif image_path.suffix.lower() == ".fits":
+                with fits.open(image_path.__str__()) as fit:
+                    image_data = fit[0].data
         except (IOError, KeyError, ValueError, TiffFileError, DeflateError) as error:
             message = f"{type(error).__name__} reading image: {image_path}: {error}"
             logger.error(message)