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diff --git a/sys/imfort/db/README b/sys/imfort/db/README new file mode 100644 index 00000000..1503a949 --- /dev/null +++ b/sys/imfort/db/README @@ -0,0 +1,120 @@ +IMFORT/DB -- Image header keyword access for IMFORT (20Apr86) + + This directory contains a version of the imio/db package, modified for +IMFORT. The modifications consisted of [1] elimination of calls to the +various printf routines, so that only pure code (no external dependencies +or use of VOS i/o) is linked into the Fortran program, [2] deleted imgnfn +template stuff, [3] added provision for comments when adding new keywords, +[4] changed datatype code to integer uniformly. Error checking is still +used but should be iferr-ed and turned into an IER code in the Fortran +binding. + + +Old IDBI readme docs: +---------------------------------------- + + Image Header Database Interface + dct 16-Apr-85 + +1. Overview + + This directory contains the first version of the image header database +interface. In this implementation the image header is a variable length fixed +format binary structure. The first, fixed format, part of the image header +contains the standard fields in binary and is fixed in size. This is followed +by the so called "user area", a string buffer containing a sequence of +variable length, newline delimited FITS format keyword=value header cards. +When an image is open a large user area is allocated to permit the addition +of new parameters without filling up the buffer. When the header is +subsequently updated on disk only as much disk space is used as is needed to +store the actual header. + +This format header is upwards compatible with the old image header format, +hence old images and programs do not have to be modified to use the IMIO +release supporting database accesss. In the future image headers will be +maintained under DBIO, but the routines in the image header database interface +are not exected to change. The actual disk format of images will of course +change when we switch over to the DBIO headers. + + + +2. Functions + + get,g - get the value of a field + put,p - set the value of a field + add,a - add a new field to a database + acc - determine if the named field exists + + +3. Procedures + + value = imget[bcsilrdx] (im, "field") + imgstr (im, "field", outstr, maxch) + imput[bcsilrdx] (im, "field", value) + impstr (im, "field", value) + imadd[bcsilrdx] (im, "field", def_value) + imastr (im, "field", def_value) + imaddf (im, "field", "datatype") + y/n = imaccf (im, "field") + + list = imofnl[su] (im, template) + nch = imgnfn (im, outstr, maxch) + imcfnl (im) + + + +4. Description + + New parameters will typically be added to the image header with either +one of the typed procedures IMADD_ or with the lower level procedure IMADDF. +The former procedures permit the parameter to be created and the value +initialized all in one call, while the latter only creates the parameter. +In addition, the typed IMADD_ procedures may be used to update the values +of existing parameters (it is not considered an error if the parameter +already exists). The principal limitation of the typed procedures is that +they may only be used to add or set parameters of a standard datatype. +The IMADDF procedure will permit creation of parameters with more descriptive +datatypes (domains) when the interface is recut upon DBIO. + +The value of any parameter may be fetched with one of the IMGET functions. +The IMACCF function may be used (like ACCESS for a file) to determine +whether a parameter exists. + +The database interface may be used to access any field of the image header, +including the following standard fields. Note that the nomenclature has +been changed slightly to make it more consistent with FITS. Additional +standard fields will be defined in the future. + + + keyword type description + + i_naxis i number of axes (dimensionality) + i_naxis[1-7] l length of an axis ("i_naxis1", etc.) + i_pixtype i pixel datatype (SPP integer code) + i_minpixval r minimum pixel value + i_maxpixval r maximum pixel value + i_ctime l time of image creation + i_mtime l time of last modify + i_limtime l time when limits (minmax) were last updated + i_title s title string + + +The names of the standard fields share an "i_" prefix to reduce the possibility +of collisions with data dependent keywords, to identify the standard fields in +sorted listings, to allow use of pattern matching to discriminate between the +standard fields and user fields, and so on. For the convenience of the user, +the "i_" prefix may be omitted provided the resultant name does not match the +name of a user parameter. It is however recommended that the full name be +used in all applications software. + + +5. Restrictions + + The use of FITS format as the internal format for storing fields in this +version of the interface places restrictions on the size of field names and +of the string value of string valued parameters. Field names are currently +limited to eight characters or less and case is ignored (since FITS requires +upper case). The eight character limit does not apply to the standard fields. +String values are limited to at most 68 characters. If put string is passed +a longer string it will be silently truncated. Trailing whitespace and +newlines are chopped when a string value is read. |