On Fri, Jul 1, 2016 at 3:18 PM, Christoph Biedl <[email protected]> wrote: > tags 771303 confirmed upstream moreinfo > thanks > > Mathieu Malaterre wrote... > >> It would be nice to add support for JPEG-XR file. For instance: >> >> $ wget -O test.jxr http://phpied.com/files/jpeg-xr/sunset-paint.wdp >> $ file test.jxr >> test.jxr: data > > Sorry for not getting back to you earlier. So ... > >> According to: >> http://www.itu.int/rec/T-REC-T.832-201201-I/en >> >> the header is defined with: >> >> A.5.2 FIXED_FILE_HEADER_II_2BYTES >> FIXED_FILE_HEADER_II_2BYTES shall be equal to 0x4949. >> A.5.3 FIXED_FILE_HEADER_0XBC_BYTE >> FIXED_FILE_HEADER_0XBC_BYTE shall be equal to 0xBC. > > ... I'm a bit reluctant here since 24 Bits of information is pretty > small and might lead to false detections. Assuming you have a bigger > collection of these files at hand: Can you confirm the version numer > (byte at offset 3) is always 0x01? Also it seems the 32bit > little-endian value at offset 4 has a very limited set of legal > values, too ("multiple of two"); which values are around in the wild?
Indeed: A.5.2 FIXED_FILE_HEADER_II_2BYTES FIXED_FILE_HEADER_II_2BYTES shall be equal to 0x4949. A.5.3 FIXED_FILE_HEADER_0XBC_BYTE FIXED_FILE_HEADER_0XBC_BYTE shall be equal to 0xBC. A.5.4 FILE_VERSION_ID FILE_VERSION_ID shall be equal to 1. Other values of FILE_VERSION_ID are reserved for future use, as modified in additional parts or amendments, by ITU-T | ISO/IEC. A.5.5 FIRST_IFD_OFFSET FIRST_IFD_OFFSET specifies the byte position, relative to the beginning of the file, of the first IMAGE_FILE_DIRECTORY( ) syntax structure (subclause A.6) in the file. The value of FIRST_IFD_OFFSET shall be an integer multiple of 2. So I would enforce FILE_VERSION_ID = 1 and FIRST_IFD_OFFSET % 2 == 0. Tested with: $ convert -size 512x512 -depth 8 xc:white -colorspace YCbCr test.jxr $ convert -size 512x512 -depth 8 xc:white test8.jxr $ convert -size 512x512 -depth 16 xc:white test16.jxr -M
