TIFFOpen(3T)TIFFOpen(3T)NAME
TIFFOpen, TIFFFdOpen, TIFFClientOpen - open a TIFF file
for reading or writing
SYNOPSIS
#include <tiffio.h>
TIFF* TIFFOpen(const char* filename, const char* mode)
TIFF* TIFFFdOpen(const int fd, const char* filename, const
char* mode)
typedef tsize_t (*TIFFReadWriteProc)(thandle_t, tdata_t,
tsize_t);
typedef toff_t (*TIFFSeekProc)(thandle_t, toff_t, int);
typedef int (*TIFFCloseProc)(thandle_t);
typedef toff_t (*TIFFSizeProc)(thandle_t);
typedef int (*TIFFMapFileProc)(thandle_t, tdata_t*,
toff_t*);
typedef void (*TIFFUnmapFileProc)(thandle_t, tdata_t,
toff_t);
TIFF* TIFFClientOpen(const char* filename, const char*
mode, thandle_t clientdata,
TIFFReadWriteProc readproc, TIFFReadWriteProc
writeproc, TIFFSeekProc seekproc,
TIFFCloseProc closeproc, TIFFSizeProc sizeproc,
TIFFMapFileProc mapproc,
TIFFUnmapFileProc unmapproc)
DESCRIPTIONTIFFOpen opens a TIFF file whose name is filename and
returns a handle to be used in subsequent calls to rou-
tines in libtiff. If the open operation fails, then zero
is returned. The mode parameter specifies if the file is
to be opened for reading (``r''), writing (``w''), or
appending (``a'') and, optionally, whether to override
certain default aspects of library operation (see below).
When a file is opened for appending, existing data will
not be touched; instead new data will be written as addi-
tional subfiles. If an existing file is opened for writ-
ing, all previous data is overwritten.
If a file is opened for reading, the first TIFF directory
in the file is automatically read (also see TIFFSetDirec-
tory(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 TIFF Revision 6.0: BitsPerSample=1, ThreshHold-
ing=bilevel art scan, FillOrder=1 (most significant bit of
each data byte is filled first), Orientation=1 (the 0th
row represents the visual top of the image, and the 0th
column represents the visual left hand side), SamplesPer-
Pixel=1, RowsPerStrip=infinity, ResolutionUnit=2 (inches),
and Compression=1 (no compression). To alter these val-
ues, or to define values for additional fields, TIFFSet-
Field(3T) must be used.
TIFFFdOpen is like TIFFOpen except that it opens a TIFF
file given an open file descriptor fd. The file's name
and mode must reflect that of the open descriptor. The
object associated with the file descriptor must support
random access.
January 9, 1996 1
TIFFOpen(3T)TIFFOpen(3T)
TIFFClientOpen is like TIFFOpen except that the caller
supplies a collection of functions that the library will
use to do UNIX-like I/O operations. The readproc and
writeproc are called to read and write data at the current
file position. seekproc is called to change the current
file position a la lseek(2). closeproc is invoked to
release any resources associated with an open file.
sizeproc is invoked to obtain the size in bytes of a file.
mapproc and unmapproc are called to map and unmap a file's
contents in memory; c.f. mmap(2) and munmap(2). The
clientdata parameter is an opaque ``handle'' passed to the
client-specified routines passed as parameters to TIFF-
ClientOpen.
OPTIONS
The open mode parameter can include the following flags in
addition to the ``r'', ``w'', and ``a'' flags. Note how-
ever that option flags must follow the read-write-append
specification.
l When creating a new file force information be writ-
ten with Little-Endian byte order (but see below).
By default the library will create new files using
the native CPU byte order.
b When creating a new file force information be writ-
ten with Big-Endian byte order (but see below). By
default the library will create new files using the
native CPU byte order.
L Force image data that is read or written to be
treated with bits filled from Least Significant Bit
(LSB) to Most Significant Bit (MSB). Note that
this is the opposite to the way the library has
worked from its inception.
B Force image data that is read or written to be
treated with bits filled from Most Significant Bit
(MSB) to Least Significant Bit (LSB); this is the
default.
H Force image data that is read or written to be
treated with bits filled in the same order as the
native CPU.
M Enable the use of memory-mapped files for images
opened read-only. If the underlying system does
not support memory-mapped files or if the specific
image being opened cannot be memory-mapped then the
library will fallback to using the normal system
interface for reading information. By default the
library will attempt to use memory-mapped files.
m Disable the use of memory-mapped files.
January 9, 1996 2
TIFFOpen(3T)TIFFOpen(3T)
C Enable the use of ``strip chopping'' when reading
images that are comprised of a single strip or tile
of uncompressed data. Strip chopping is a mecha-
nism by which the library will automatically con-
vert the single-strip image to multiple strips,
each of which has about 8 Kilobytes of data. This
facility can be useful in reducing the amount of
memory used to read an image because the library
normally reads each strip in its entirety. Strip
chopping does however alter the apparent contents
of the image because when an image is divided into
multiple strips it looks as though the underlying
file contains multiple separate strips. Finally,
note that default handling of strip chopping is a
compile-time configuration parameter. The default
behaviour, for backwards compatibility, is to
enable strip chopping.
c Disable the use of strip chopping when reading
images.
BYTE ORDER
The TIFF specification (all versions) states that compli-
ant readers must be capable of reading images written in
either byte order. Nonetheless some software that claims
to support the reading of TIFF images is incapable of
reading images in anything but the native CPU byte order
on which the software was written. (Especially notorious
are applications written to run on Intel-based machines.)
By default the library will create new files with the
native byte-order of the CPU on which the application is
run. This ensures optimal performance and is portable to
any application that conforms to the TIFF specification.
To force the library to use a specific byte-order when
creating a new file the ``b'' and ``l'' option flags may
be included in the call to open a file; for example,
``wb'' or ``wl''.
RETURN VALUES
Upon successful completion TIFFOpen, TIFFFdOpen, and TIFF-
ClientOpen return a TIFF pointer. Otherwise, NULL is
returned.
DIAGNOSTICS
All error messages are directed to the TIFFError(3T) rou-
tine. Likewise, warning messages are directed to the
TIFFWarning(3T) routine.
"%s": Bad mode. The specified mode parameter was not one
of ``r'' (read), ``w'' (write), or ``a'' (append).
%s: Cannot open. TIFFOpen() was unable to open the speci-
fied filename for read/writing.
January 9, 1996 3
TIFFOpen(3T)TIFFOpen(3T)
Cannot read TIFF header. An error occurred while attempt-
ing to read the header information.
Error writing TIFF header. An error occurred while writ-
ing the default header information for a new file.
Not a TIFF file, bad magic number %d (0x%x). The magic
number in the header was not (hex) 0x4d4d or (hex) 0x4949.
Not a TIFF file, bad version number %d (0x%x). The ver-
sion field in the header was not 42 (decimal).
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.
SEE ALSOlibtiff(3T), TIFFClose(3T)
January 9, 1996 4
