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=pod
=head1 NAME
B<FunRef: the Funtools Reference Handle>
=head1 SYNOPSIS
A description of how to use a Funtools reference handle to connect a
Funtools input file to an output file.
=head1 DESCRIPTION
The Funtools reference handle connects a Funtools input file to a
Funtools output file so that parameters (or even whole extensions) can
be copied from the one to the other. To make the connection, the Funtools
handle of the input file is passed to the
final argument of the
FunOpen() call for the output file:
if( !(ifun = FunOpen(argv[1], "r", NULL)) )
gerror(stderr, "could not FunOpen input file: %s\n", argv[1]);
if( !(ofun = FunOpen(argv[2], "w", ifun)) )
gerror(stderr, "could not FunOpen output file: %s\n", argv[2]);
It does not matter what type of input or output file (or extension) is
opened, or whether they are the same type. When the output image or
binary table is written using
FunImagePut()
or
FunTableRowPut()
an appropriate header will be written first, with parameters copied
from the input extension. Of course, invalid parameters will be
removed first, e.g., if the input is a binary table and the output is
an image, then binary table parameters such as TFORM, TUNIT,
etc. parameters will not be copied to the output.
Use of a reference handle also allows default values to be passed
to
FunImagePut() in order to
write out an output image with the same dimensions and data type
as the input image. To use the defaults from the input, a value
of 0 is entered for dim1, dim2, and bitpix. For example:
fun = FunOpen(argv[1], "r", NULL);
fun2 = FunOpen(argv[2], "w", fun);
buf = FunImageGet(fun, NULL, NULL);
... process image data ...
FunImagePut(fun2, buf, 0, 0, 0, NULL);
Of course, you often want to get information about the data type
and dimensions of the image for processing. The above code
is equivalent to the following:
fun = FunOpen(argv[1], "r", NULL);
fun2 = FunOpen(argv[2], "w", fun);
buf = FunImageGet(fun, NULL, NULL);
FunInfoGet(fun, FUN_SECT_DIM1, &dim1, FUN_SECT_DIM2, &dim2,
FUN_SECT_BITPIX, &bitpix, 0);
... process image data ...
FunImagePut(fun2, buf, dim1, dim2, bitpix, NULL);
It is possible to change the reference handle for a given output Funtools
handle using the
FunInfoPut() routine:
/* make the new extension the reference handle for the output file */
FunInfoPut(fun2, FUN_IFUN, &fun, 0);
When this is done, Funtools specially resets the output file to start
a new output extension, which is connected to the new input reference
handle. You can use this mechanism to process multiple input extensions
into a single output file, by successively opening the former and
setting the reference handle for the latter. For example:
/* open a new output FITS file */
if( !(fun2 = FunOpen(argv[2], "w", NULL)) )
gerror(stderr, "could not FunOpen output file: %s\n", argv[2]);
/* process each input extension in turn */
for(ext=0; ;ext++){
/* get new extension name */
sprintf(tbuf, "%s[%d]", argv[1], ext);
/* open it -- if we cannot open it, we are done */
if( !(fun=FunOpen(tbuf, "r", NULL)) )
break;
/* make the new extension the reference handle for the output file */
FunInfoPut(fun2, FUN_IFUN, &fun, 0);
... process ...
/* flush output extension (write padding, etc.) */
FunFlush(fun2, NULL);
/* close the input extension */
FunClose(fun);
}
In this example, the output file is opened first. Then each successive
input extension is opened, and the output reference handle is set to
the newly opened input handle. After data processing is performed, the
output extension is flushed and the input extension is closed, in
preparation for the next input extension.
Finally, a reference handle can be used to copy other extensions from
the input file to the output file. Copy of other extensions is
controlled by adding a "C" or "c" to the mode string of the
FunOpen()
call B<of the input reference file>. If "C" is specified, then
other extensions are B<always> copied (i.e., copy is forced by the
application). If "c" is used, then other extensions are copied if the
user requests copying by adding a plus sign "+" to the extension name
in the bracket specification. For example, the B<funtable>
program utilizes user-specified "c" mode so that the second example
below will copy all extensions:
# copy only the EVENTS extension
csh> funtable "test.ev[EVENTS,circle(512,512,10)]" foo.ev
# copy ALL extensions
csh> funtable "test.ev[EVENTS+,circle(512,512,10)]" foo.ev
When extension copy is specified in the input file, the call to
FunOpen()
on the input file delays the actual file open until the output file
also is opened (or until I/O is performed on the input file, which
ever happens first). Then, when the output file is opened, the input
file is also opened and input extensions are copied to the output
file, up to the specific extension being opened. Processing of input
and output extensions then proceed.
When extension processing is complete, the remaining extensions need to
be copied from input to output. This can be done explicitly, using the
FunFlush()
call with the "copy=remaining" plist:
FunFlush(fun, "copy=remaining");
Alternatively, this will happen automatically, if the output file
is closed B<before> the input file:
/* we could explicitly flush remaining extensions that need copying */
/* FunFlush(fun2, "copy=remaining"); */
/* but if we close output before input, end flush is done automatically */
FunClose(fun2);
FunClose(fun);
=head1 SEE ALSO
See funtools(n) for a list of Funtools help pages
=cut
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