JEITA  CP-3451 - 71 - Figure 32 Procedure for Image Data Reproduction Some off-the-shelf software lacks a function for handling valid image width and height tags. If the valid image width differs from the number of horizontal pixels recorded in the SOF, padding data may be displayed. The padding data values should be chosen with this possibility in mind. 4.8.2   Stipulations on Thumbnails A.    Exif writer The recording of thumbnail images is an optional specification of the Exif reader. It is therefore allowable to have Exif files with and without thumbnails. For details see section 4.5.5. B.    Exif reader This format is designed so that the primary image will be reproduced intact whether or not thumbnail images are recorded  in  the  file.  It  is  assumed  that  even  when  functions  are  provided  for  viewing  images  on  the  camera  or player, for viewing the process of image transfer from camera to PC, or for using thumbnails as an index display in the camera software or other image software, there will still be cases where the file is viewed without thumbnails. The creation and displaying of thumbnails can therefore be performed or not at the discretion of the user. 4.8.3   File Name Stipulations A.    Exif writer The  file  name  and  characters  used  for  file  names  are  not  specified,  other  than  to  stipulate  the  use  of  ASCII alphanumerics.  (File  names  in  Japanese  or  other  character  sets  are  not  to  be  used.)  File  names  shall  be  8 characters or fewer, not including the extension. (Long file names are not to be used.) The file name extensions are ".JPG" for compressed data files and ".TIF" for uncompressed data files. 4.8.4   Byte Order Stipulations A.    Exif Reader It is recommended that the Exif reader be able to reproduce Exif files recorded in both little endian and big endian formats. PixelX/YDimension = SOF.X,SOF.Y ? Trimming with PixelX/YDimension JPEG Decompression based on SOF.X, SOF.Y No Yes