don't overwrite eps image size

Author: Yay295

Tests/images/eps/1.bmp

@@ -334,7 +334,8 @@ def _read_comment(s: str) -> bool:
  else:
  break
 
- self._size = columns, rows
+ if not self._size:
+ self._size = columns, rows
  return
  elif bytes_mv[:5] == b"%%EOF":
  break