MAINT: Increase readability in CCITTFaxDecode (py-pdf#3416)

params.group is not always equal to 4, so the comment is changed.

Author: j-t-1

pypdf/filters.py

@@ -631,44 +631,44 @@ def decode(
         tiff_header = struct.pack(
             tiff_header_struct,
             b"II",  # Byte order indication: Little endian
-            42,  # Version number (always 42)
-            8,  # Offset to first IFD
-            8,  # Number of tags in IFD
-            256,
+            42,     # Version number (always 42)
+            8,      # Offset to the first image file directory (IFD)
+            8,      # Number of tags in IFD
+            256,    # ImageWidth, LONG, 1, width
             4,
             1,
-            params.columns,  # ImageWidth, LONG, 1, width
-            257,
+            params.columns,
+            257,    # ImageLength, LONG, 1, length
             4,
             1,
-            params.rows,  # ImageLength, LONG, 1, length
-            258,
+            params.rows,
+            258,    # BitsPerSample, SHORT, 1, 1
             3,
             1,
-            1,  # BitsPerSample, SHORT, 1, 1
-            259,
+            1,
+            259,    # Compression, SHORT, 1, compression Type
             3,
             1,
-            params.group,  # Compression, SHORT, 1, 4 = CCITT Group 4 fax encoding
-            262,
+            params.group,
+            262,    # Thresholding, SHORT, 1, 0 = BlackIs1
             3,
             1,
-            0,  # Thresholding, SHORT, 1, 0 = WhiteIsZero
-            273,
+            0,
+            273,    # StripOffsets, LONG, 1, length of header
             4,
             1,
-            struct.calcsize(
+              struct.calcsize(
                 tiff_header_struct
-            ),  # StripOffsets, LONG, 1, length of header
-            278,
+            ),
+            278,    # RowsPerStrip, LONG, 1, length
             4,
             1,
-            params.rows,  # RowsPerStrip, LONG, 1, length
-            279,
+            params.rows,
+            279,    # StripByteCounts, LONG, 1, size of image
             4,
             1,
-            img_size,  # StripByteCounts, LONG, 1, size of image
-            0,  # last IFD
+            img_size,
+            0,      # last IFD
         )
 
         return tiff_header + data