rfc1314.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

      architecture or visual characteristics of an image.  The following
      Basic Fields should be included in a TIFF image file:

           FIELD NAME
       (TAG in hex, TYPE)       VALUE           DESCRIPTION
       ------------------       -----           -----------

         BitsPerSample            1             Number of bits
          (0102, SHORT)                         per pixel (bi-level for
                                                now, but may allow
                                                more later)

         Compression              4             Type of Compression
          (0103, SHORT)      (could also be       1 = Uncompressed
                                1 or 3)           3 = G3 (MH or MR)
                                                  4 = G4 (MMR)
                                                 Use 4 if possible

         ImageLength       <image's length>     Length of the Image
          (0101, SHORT                             in scan lines
            or LONG)

         ImageWidth         <image's width>     Width of the Image
          (0100, SHORT                             in pixels



Katz & Cohen                                                   [Page 12]

RFC 1314                 Image Exchange Format                April 1992


            or LONG)

         NewSubFileType     0 usually           Flag bits indicating
          (00FE, LONG)       bit 0: 1 if           the kind of image.
                              reduced           (see the TIFF
                              resolution of        reference [3])
                              another image
                             bit 1: 1 if
                              single page of a
                              multi-page image
                             bit 2: 1 if
                              image defines a
                              transparency
                              mask

         Photometric-       0 for positive
           Interpretation    image (0 imaged
          (0106, SHORT)      as white, 1 as
                             black)
                            1 means reverse
                             black and white

         RowsPerStrip    <Number of Rows>       Number of Rows in
          (0116, SHORT                          Each Strip.  Each
           or LONG)                             page should be a
                                                single strip.

         SamplesPerPixel          1             (since are Bi-level
          (0115, SHORT)                          images)

         StripByteCounts    count1, count2...   Number of Bytes in
          (0117, SHORTs                          each strip of the
            or LONGs)                            images.  (The Value
                                                 is an offset which
                                                 points to a series
                                                 of counts, each of
                                                 which is the same
                                                 Type, LONG or SHORT.
                                                 The Length is the
                                                 same as the number
                                                 of strips.)

         StripOffsets       off1, off2,...      Pointers to the strips
          (0111, SHORTs                          of the image (remember,
            or LONGs)                            one strip per page).
                                                 (The Value is an offset
                                                  which points to a
                                                  series of offsets,



Katz & Cohen                                                   [Page 13]

RFC 1314                 Image Exchange Format                April 1992


                                                  each of which points
                                                  to the actual image
                                                  data for the strip.)

         ResolutionUnit         2 | 3           Units of Resolution
          (0128, SHORT)      See Below, 3.C.6     2: Inches
                                                  3: Centimeters

         XResolution        See Below, 3.C.6    Resolution in the X
          (011A, RATIONAL)                       direction in pixels
                                                 per ResolutionUnit
                                                 (we suggest 400 dots
                                                 per inch when possible)

         YResolution        See Below, 3.C.6    Resolution in the Y
          (011B, RATIONAL)                        direction in pixels
                                                 per ResolutionUnit
                                                 (we suggest 400 dots
                                                 per inch when possible)

   3.C.2.  Informational Fields (Optional)

      The following Informational Fields are optional.  They provide
      useful information to a user.  All Field values are ASCII strings.

       NAME (TAG in hex)                DESCRIPTION
       ----------------                 -----------

         Artist (013B)           Person Who Created the Image

         DateTime (0132)         Date and Time of Image Creation

         HostComputer (013C)     Name of Computer Image was Created On

         ImageDescription        A Short Text Description
           (010E)

         Make (010F)             Manufacturer of Hardware (Scanner) Used

         Model (0110)            Model Number of Hardware (Scanner) Used

         Software (0131)         Software Package that Created the Image

   3.C.3.  Facsimile Fields (Optional, Mandatory for G3 Compression)

      In addition to the above, the Facsimile Fields below should be
      used.  The TIFF document recommends that they not be used for
      interchange between applications, but they are now in wide enough



Katz & Cohen                                                   [Page 14]

RFC 1314                 Image Exchange Format                April 1992


      use for just that.  These fields are optional and default to 0
      (all bits off).

           FIELD NAME
       (TAG in hex, TYPE)       VALUE               DESCRIPTION
       ------------------       -----               -----------

         Group3Options      bit 0: 1 for         Flag bits indicating
          (0124, LONG)       2-dimensional       Options for G3
                             coding
                              (i.e., MR with
                               k > 1)
                            bit 1: 1 if
                             uncompressed
                             mode MAY be used,
                             0 if uncompressed
                             mode IS NOT used.
                            bit 2: 1 if fill     (As allowed by the G3
                             bits have been       protocol, fill bits
                             added                may be added between
                                                  each line of data
                                                  and the EOL.  Since
                                                  fill bits are used to
                                                  "byte-align" G3 image
                                                  files, bit 2 should be
                                                  set to 1 for these
                                                  images.)


         Group4Options      bit 0: unused        Flag bits indicating
          (0125, LONG)      bit 1: 1 if          Options for G4
                             uncompressed
                             mode MAY be used,
                             if this bit is 0
                             it means that
                             uncompressed mode
                             IS NOT used.

   3.C.4.  Storage and Retrieval Fields (Optional)

      The following fields are optional and may be useful for document
      storage and retrieval.









Katz & Cohen                                                   [Page 15]

RFC 1314                 Image Exchange Format                April 1992


           FIELD NAME
       (TAG in hex, TYPE)                DESCRIPTION
       ------------------                -----------

         DocumentName               Name of the Document
          (010D, ASCII)

         PageName                   Name of the Page
          (011D, ASCII)

         PageNumber                 Page Number in a Multi-Page Document
          (0129, SHORTs)             Two SHORT Values are specified, the
                                     first is the page number and the
                                     second is the total number of pages
                                     in the document.  The first page
                                     is page 0.  (NOTE:  This does not
                                     necessarily correspond to page
                                     numbers which may be printed
                                     in the image.)

         XPosition                  X Offset of the Left Side of
          (011E, RATIONAL)          the Image, in ResolutionUnits

         YPosition                  Y Offset of the Top of
          (011F, RATIONAL)          the Image, in ResolutionUnits

   3.C.5.  TIFF-F Fields (NOT Recommended)

      TIFF-F defines the following new fields for G3 (MH) encoded
      images.  Since these fields are not defined in TIFF-B itself,
      their use is not recommended.  However, since TIFF-F files may
      include these tags for image data which came from a G3 fax
      machine, readers should be prepared for them.

      These three fields deal with corrupted image data which is due to
      the fact that G3 devices may not perform error correction on bad
      data.

           FIELD NAME
       (TAG in hex, TYPE)                DESCRIPTION
       ------------------                -----------

         BadFaxLines                Number of Bad fax scan lines
          (0146, SHORT or LONG)     encountered during fax reception
                                    (but not necessarily in the file)

         CleanFaxData               0 means no bad lines received
          (0147, SHORT)             1 means bad lines were regenerated



Katz & Cohen                                                   [Page 16]

RFC 1314                 Image Exchange Format                April 1992


                                        by the receiving device
                                    2 means bad lines were detected
                                        but not regenerated

        ConsecutiveBadFaxLines      The maximum number of consecutive
          (0148, SHORT or LONG)     bad fax lines (but not necessarily
                                    in the file)

   3.C.6.  More on Representing Resolutions

      The tags XResolution and YResolution are both RATIONALs, i.e., the
      ratio of two LONGS.  G3 fax resolutions are actually specified in
      dots (or lines) per mm while G4 is in dots per inch (actually,
      dots per 25.4 mm).

      For example, G3 horizontal resolution is defined to be 1728 dots
      per 215 mm which comes out to 80.4 dots per cm or about 203 dots
      per inch.  It is frequently referred to as just 200 dpi.  To avoid
      any possibility of problems due to round off error, this should be
      represented by having XResolution = 17280/215 and ResolutionUnit =
      3 (cm).  However when reading, 204/1 or even 200/1 with
      ResolutionUnit = 2 (inches) should be recognized as representing
      the same resolution.

      For G4, on the other hand, the resolution 400 dots/inch should be
      represented by an XResolution of 400/1 and ResolutionUnit = 2.

      The following table shows various ways of representing the
      standard resolutions in order of preference:


                   ResolutionUnit    XResolution       YResolution
                   --------------    -----------       -----------

        G3 normal       3             17280/215         3850/100
                        3                80/1           3850/100
                        3             17280/215          385/10
                        3                80/1            385/10
                        2              2042/10          9779/100
                        2               204/1             98/1
                        2               200/1            100/1

        G3 fine         3             17280/215           77/1
                        3                80/1             77/1
                        2              2042/10         19558/100
                        2               204/1            196/1
                        2               200/1            200/1




Katz & Cohen                                                   [Page 17]

RFC 1314                 Image Exchange Format                April 1992


        G4 200 dpi      2               200/1            200/1

        G4 300 dpi      2               300/1            300/1

        Other 300 dpi   2               300/1            300/1

        G4 400 dpi      2               400/1            400/1

        600 dpi         2               600/1            600/1

      It is suggested that Image readers be able to handle all of the