CCfits - HEASARC - NASA

6 Writing Primary Images and Image Extensions 12
nearly all functions return a non-zero status code on error, and have a final argument
status of type int):
if ( [cfitsio call](args,...,&status)) throw FitsError(status);
FitsError, derived from FitsException, uses a cfitsio library call to convert the status
code to a string message.
The few exceptions that are not derived from FitsException indicate fatal conditions
implying bugs in the library. These print a message suggesting the user contact HEA-
SARC to report the problem.
Note also the lack of statements for closing files in any of the following routines, The
destructor (dtor) for the FITS object does this when it falls out of scope. A call
FITS::destroy() throw()
is provided for closing files explicitly; destroy() is also responsible for cleaning up the
FITS object and deallocating its resources.
When the data are being read instead of written, the user is expected to copy the data
into other program variables [rather than use references to the data contained in the
FITS object].
The routines in this program test the following functionality:
writeImage() Writing Primary Images and Image Extensions
writeAscii() Creating and Writing to an Ascii Table Extension
writeBinary() Creating and Writing to a Binary Table Extension
copyHDU() Copying an Extension between Files
selectRows() Selecting Table Data
readHeader() Reading Header information from a HDU
readImage() Reading an Image
readTable() Reading a Table Extension
readExtendedSyntax() Reading with Extended File Name Syntax
6 Writing Primary Images and Image Extensions
This section of the code demonstrates creation of images. Because every fits file must
have a PHDU element, all the FITS constructors (ctors) instantiate a PHDU object.
In the case of a new file, the default is to establish an empty HDU with BITPIX = 8
(BYTE_IMG). A current limitation of the code is that the data type of the PHDU
cannot be replaced after the FITS file is created. Arguments to the FITS ctors allow
the specification of the data type and the number of axes and their lengths. An image
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