.help impixf Sep86 imfort
.ih
NAME
impixf -- get the physical attributes of the pixel file
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SYNOPSIS
.nf
subroutine impixf (im, pixfd, pixfil, pixoff, szline, ier)

integer		im		#I image descriptor of open image
integer		pixfd		#O BFIO file descriptor of pixel file
character*(*)	pixfil		#O host filename of pixel file
integer		pixoff		#O 1-indexed "char" offset of pixels
integer		szline		#O "chars" per physical image line
integer		ier		#O status return
.fi
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DESCRIPTION
The \fIimpixf\fR procedure is used to obtain information describing the
physical layout of the pixel segment of an image in a binary disk file.
The pixel array of an image accessible via the IMFORT interface is stored
externally in the host file \fIpixfil\fR in line storage mode (as in a
Fortran array).  Each line of the image is stored as a contiguous array of
pixels accessible via a BFIO \fIbfread\fR or \fIbfwrit\fR request at the
offset of the first pixel in the line.  The first image line (beginning at
pixel [1,1,1,...]) is stored at the file offset given by \fIpixoff\fR.
Each line consumes exactly \fIszline\fR chars of storage; lines may be
blocked to fill an integral number of disk blocks for more efficient access,
hence \fIszline\fR is not directly computable from \fIaxlen(1)\fR.

Since \fIimpixf\fR is called on an open image, the pixel file will already
have been opened for random access buffered binary file i/o via the BFIO
interface.  The BFIO file descriptor of the open pixel file is returned in
\fIpixfd\fR.  This may be used in conjunction with BFIO to directly access
the pixel data.  If the pixel data is to be accessed via explicit calls
to lower level host system facilities, the image should first be closed
with \fIimclos\fR to avoid possible problems with having the same file
opened multiple times.
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RETURN VALUE
A zero status is returned for any image which has a valid image descriptor.

IE_MAGIC:	illegal imfort image descriptor
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NOTES
Programs which make use of the information provided by \fIimpixf\fR have
explicit knowledge of the physical image storage format and hence may not
work with future versions of the IMFORT interface supporting new physical
image storage formats.
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SEE ALSO
imgsiz, imgs, imps, imgl, impl, bfread, bfwrit
.endhelp