path: root/man/TIFFOpen.3t

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.if n .po 0
.TH TIFFOpen 3T "February 14, 1992"
.SH NAME
TIFFOpen, TIFFFdOpen, TIFFClientOpen \- open a
.SM TIFF
file for reading or writing
.SH SYNOPSIS
.nf
.B "#include <tiffio.h>"
.B "TIFF* TIFFOpen(const char* filename, const char* mode)"
.sp 5p
.B "TIFF* TIFFFdOpen(const int fd, const char* filename, const char* mode)"
.sp 5p
.B "typedef tsize_t (*TIFFReadWriteProc)(thandle_t, tdata_t, tsize_t);"
.B "typedef toff_t (*TIFFSeekProc)(thandle_t, toff_t, int);"
.B "typedef int (*TIFFCloseProc)(thandle_t);"
.B "typedef toff_t (*TIFFSizeProc)(thandle_t);"
.B "typedef int (*TIFFMapFileProc)(thandle_t, tdata_t*, toff_t*);"
.B "typedef void (*TIFFUnmapFileProc)(thandle_t, tdata_t, toff_t);"
.sp 5p
.B "TIFF* TIFFClientOpen(const char* filename, const char* mode, thandle_t clientdata,"
.B "    TIFFReadWriteProc readproc, TIFFReadWriteProc writeproc, TIFFSeekProc seekproc,"
.B "    TIFFCloseProc closeproc, TIFFSizeProc sizeproc, TIFFMapFileProc mapproc,"
.B "    TIFFUnmapFileProc unmapproc)"
.fi
.SH DESCRIPTION
.IR TIFFOpen
opens a
.SM TIFF
file whose name is
.I filename
and returns a handle to be used in subsequent calls to routines in
.IR libtiff .
If the open operation fails, then zero is returned.
The
.I mode
parameter specifies if the file is to be opened for reading (``r''),
writing (``w''), or appending (``a'').
When a file is opened for appending, existing data will not
be touched; instead new data will be written as additional subfiles.
If an existing file is opened for writing, all previous data is
overwritten.
.PP
If a file is opened for reading, the first
.SM TIFF
directory in the file is automatically read
(also see
.IR TIFFSetDirectory (3T)
for reading directories other than the first).
If a file is opened for writing or appending, a default directory
is automatically created for writing subsequent data.
This directory has all the default values specified in
.SM TIFF
Revision 6.0:
.IR BitsPerSample =1,
.IR ThreshHolding "=bilevel art scan,"
.IR FillOrder =1
(most significant bit of each data byte is filled first),
.IR Orientation =1
(the 0th row represents the visual top of the image, and the 0th
column represents the visual left hand side),
.IR SamplesPerPixel =1,
.IR RowsPerStrip =infinity,
.IR ResolutionUnit =2
(inches), and
.IR Compression =1
(no compression).
To alter these values, or to define values for additional fields,
.IR TIFFSetField (3T)
must be used.
.PP
It is not possible to append data to a file that has a
byte ordering opposite to the native byte ordering of a machine.
That is, for example, the library will not allow
a file with little-endian byte ordering to be appended to
on a machine that has a native big-endian byte ordering.
.PP
.IR TIFFFdOpen
is like
.IR TIFFOpen
except that it opens a
.SM TIFF
file given an open file descriptor
.IR fd .
The file's name and mode must reflect that of the open descriptor.
The object associated with the file descriptor
.BR "must support random access" .
.PP
.IR TIFFClientOpen
is like
.IR TIFFOpen
except that the caller supplies a collection of functions that the
library will use to do \s-1UNIX\s+1-like I/O operations. 
The
.I readproc
and
.I writeproc
are called to read and write data at the current file position.
.I seekproc
is called to change the current file position a la
.IR lseek (2).
.I closeproc
is invoked to release any resources associated with an open file.
.I sizeproc
is invoked to obtain the size in bytes of a file.
.I mapproc
and
.I unmapproc
are called to map and unmap a file's contents in memory; c.f.
.IR mmap (2)
and
.IR munmap (2).
The
.I clientdata
parameter is an opaque ``handle'' passed to the client-specified
routines passed as parameters to
.IR TIFFClientOpen .
.SH "RETURN VALUES"
Upon successful completion 
.IR TIFFOpen ,
.IR TIFFFdOpen ,
and
.IR TIFFClientOpen
return a 
.SM TIFF
pointer.
Otherwise, NULL is returned.
.SH DIAGNOSTICS
All error messages are directed to the
.IR TIFFError (3T)
routine.
Likewise, warning messages are directed to the
.IR TIFFWarning (3T)
routine.
.PP
\fB"%s": Bad mode\fP.
The specified
.I mode
parameter was not one of ``r'' (read), ``w'' (write), or ``a'' (append).
.PP
.BR "%s: Cannot open" .
.IR TIFFOpen ()
was unable to open the specified filename for read/writing.
.PP
.BR "Cannot read TIFF header" .
An error occurred while attempting to read the header information.
.PP
.BR "Error writing TIFF header" .
An error occurred while writing the default header information
for a new file.
.PP
.BR "Not a TIFF file, bad magic number %d (0x%x)" .
The magic number in the header was not (hex)
0x4d4d or (hex) 0x4949.
.PP
.BR "Not a TIFF file, bad version number %d (0x%x)" .
The version field in the header was not 42 (decimal).
.PP
.BR "Cannot append to file that has opposite byte ordering" .
A file with a byte ordering opposite to the native byte
ordering of the current machine was opened for appending (``a'').
This is a limitation of the library.
.SH "SEE ALSO"
.IR libtiff (3T),
.IR TIFFClose (3T)