Simplified code

src/PIL/SgiImagePlugin.py

@@ -82,17 +82,10 @@ class SgiImageFile(ImageFile.ImageFile):
         # zsize : channels count
         zsize = i16(s, 10)
 
-        # layout
-        layout = bpc, dimension, zsize
-
         # determine mode from bits/zsize
-        rawmode = ""
         try:
-            rawmode = MODES[layout]
+            rawmode = MODES[(bpc, dimension, zsize)]
         except KeyError:
-            pass
-
-        if rawmode == "":
             msg = "Unsupported SGI image mode"
             raise ValueError(msg)
 
@@ -156,24 +149,15 @@ def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
     # Run-Length Encoding Compression - Unsupported at this time
     rle = 0
 
-    # Number of dimensions (x,y,z)
-    dim = 3
     # X Dimension = width / Y Dimension = height
     x, y = im.size
-    if im.mode == "L" and y == 1:
-        dim = 1
-    elif im.mode == "L":
-        dim = 2
     # Z Dimension: Number of channels
     z = len(im.mode)
-
-    if dim in {1, 2}:
-        z = 1
-
-    # assert we've got the right number of bands.
-    if len(im.getbands()) != z:
-        msg = f"incorrect number of bands in SGI write: {z} vs {len(im.getbands())}"
-        raise ValueError(msg)
+    # Number of dimensions (x,y,z)
+    if im.mode == "L":
+        dim = 1 if y == 1 else 2
+    else:
+        dim = 3
 
     # Minimum Byte value
     pinmin = 0