TIFFOPEN(3tiff) LibTIFF TIFFOPEN(3tiff)
NAME
TIFFOpen - open a TIFF file for reading or writing
SYNOPSIS
#include <tiffio.h>
TIFF *TIFFOpen(const char *filename, const char *mode)
TIFF *TIFFOpenW(const wchar_t *name, const char *mode)
TIFF *TIFFFdOpen(const int fd, const char *filename, const char *mode)
TIFF *TIFFOpenExt(const char *filename, const char *mode,
TIFFOpenOptions *opts)
TIFF *TIFFOpenWExt(const wchar_t *name, const char *mode,
TIFFOpenOptions *opts)
TIFF *TIFFFdOpenExt(const int fd, const char *filename, const char
*mode, TIFFOpenOptions *opts)
const char *TIFFSetFileName(TIFF *tif)
int TIFFSetFileno(TIFF *tif, int fd)
int TIFFSetMode(TIFF *tif, int 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)
TIFF *TIFFClientOpenExt(const char *filename, const char *mode,
thandle_t clientdata, TIFFReadWriteProc readproc, TIFFReadWriteProc
writeproc, TIFFSeekProc seekproc, TIFFCloseProc closeproc, TIFFSizeProc
sizeproc, TIFFMapFileProc mapproc, TIFFUnmapFileProc unmapproc,
TIFFOpenOptions *opts)
thandle_t TIFFClientdata(TIFF *tif)
thandle_t TIFFSetClientdata(TIFF *tif, thandle_t newvalue)
DESCRIPTION
TIFFOpen() opens a TIFF file whose name is filename and returns a han-
dle to be used in subsequent calls to routines in libtiff. If the open
operation fails, then NULL (0) is returned. The mode parameter speci-
fies if the file is to be opened for reading (r), writing (w), or ap-
pending (a) and, optionally, whether to override certain default as-
pects of library operation (see below). When a file is opened for ap-
pending, 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.
If a file is opened for reading, the first TIFF directory in the file
is automatically read (also see TIFFSetDirectory() for reading directo-
ries other than the first). If a file is opened for writing or append-
ing, a default directory is automatically created for writing subse-
quent data. This directory has all the default values specified in
TIFF Revision 6.0:
• BitsPerSample = 1,
• ThreshHolding = "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),
• SamplesPerPixel = 1,
• RowsPerStrip = ∞,
• ResolutionUnit = 2 (inches), and
• Compression = 1 (no compression).
To alter these values, or to define values for additional fields,
TIFFSetField() must be used.
A file can also be opened for reading and writing with mode (r+). In
this case, the first TIFF directory in the file is automatically read,
but calls to TIFFSetField() are put into a fresh directory, which will
be appended when the file is closed.
TIFFOpenW() opens a TIFF file with a Unicode filename, for read/writ-
ing.
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. In order to close a TIFF file opened with
TIFFFdOpen() first TIFFCleanup() should be called to free the internal
TIFF structure without closing the file handle and afterwards the file
should be closed using its file descriptor fd.
TIFFOpenExt() (added in libtiff 4.5) is like TIFFOpen(), but options,
such as re-entrant error and warning handlers may be passed with the
opts argument. The opts argument may be NULL. Refer to TIFFOpenOptions
for allocating and filling the opts argument parameters. The allocated
memory for TIFFOpenOptions can be released straight after successful
execution of the related "TIFFOpenExt" functions.
TIFFOpenWExt() (added in libtiff 4.5) is like TIFFOpenExt(), but opens
a TIFF file with a Unicode filename.
TIFFFdOpenExt() (added in libtiff 4.5) is like TIFFFdOpen(), but op-
tions, such as re-entrant error and warning handlers may be passed with
the opts argument. The opts argument may be NULL. Refer to
TIFFOpenOptions for filling the opts argument.
TIFFSetFileName() sets the file name in the tif-structure and returns
the old file name.
TIFFSetFileno() overwrites a copy of the open file's I/O descriptor,
that was saved when the TIFF file was first opened, and returns the
previous value. See note below.
TIFFSetMode() sets the libtiff open mode in the tif-structure and re-
turns the old mode.
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 functions are called to read
and write data at the current file position. seekproc is called to
change the current file position à la lseek() (2). closeproc is in-
voked to release any resources associated with an open file. sizeproc
is invoked to obtain the size in bytes of a file. mapproc and unmap-
proc 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 TIFFClientOpen().
TIFFClientOpenExt() (added in libtiff 4.5) is like TIFFClientOpen(),
but options argument opts like for TIFFOpenExt() can be passed.
TIFFClientdata() returns open file's clientdata handle, which is the
real open file's I/O descriptor used by libtiff. Note: Within
tif_unix.c this handle is converted into an integer file descriptor.
TIFFSetClientdata() sets open file's clientdata, and return previous
value. The clientdata is used as open file's I/O descriptor within
libtiff.
NOTE:
clientdata is used as file descriptor or handle of the opened TIFF
file within libtif, whereas the file descriptor fd (changeable by
TIFFSetFileno()) is only set once to the value of clientdata con-
verted to an integer (in tif_win32.c as well as in tif_unix.c).
When updating the file's clientdata with TIFFSetClientdata(), the fd
value is not updated.
OPTIONS
The open mode parameter can include the following flags in addition to
the r, w, and a flags. Note however that option flags must follow the
read-write-append specification.
l:
When creating a new file force information be written with Lit-
tle-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 written with Big-En-
dian 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 li-
brary will fallback to using the normal system interface for reading
information. By default the library will attempt to use mem-
ory-mapped files.
m:
Disable the use of memory-mapped files.
C:
Enable the use of "strip chopping" when reading images that are com-
prised of a single strip or tile of uncompressed data. Strip chop-
ping is a mechanism by which the library will automatically convert
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 de-
fault behaviour, for backwards compatibility, is to enable strip
chopping.
c:
Disable the use of strip chopping when reading images.
h:
Read TIFF header only, do not load the first image directory. That
could be useful in case of the broken first directory. We can open
the file and proceed to the other directories.
4:
ClassicTIFF for creating a file (default)
8:
BigTIFF for creating a file.
D:
Enable use of deferred strip/tile offset/bytecount array loading.
They will be loaded the first time they are accessed to. This load-
ing will be done in its entirety unless the O flag is also speci-
fied.
O:
On-demand loading of values of the strip/tile offset/bytecount ar-
rays, limited to the requested strip/tile, instead of whole array
loading (implies D)
BYTE ORDER
The TIFF specification (all versions) states that compliant 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
TIFFClientOpen() return a TIFF pointer. Otherwise, NULL is returned.
DIAGNOSTICS
All error messages are directed to the TIFFErrorExtR() routine. Like-
wise, warning messages are directed to the TIFFWarningExtR() 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 specified filename for read/writ-
ing.
"Cannot read TIFF header":
An error occurred while attempting to read the header information.
"Error writing TIFF header":
An error occurred while writing 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 version 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 limita-
tion of the library.
SEE ALSO
libtiff (3tiff), TIFFClose (3tiff), TIFFStrileQuery, TIFFOpenOptions
AUTHOR
LibTIFF contributors
COPYRIGHT
1988-2023, LibTIFF contributors
4.5 Nov 23, 2023 TIFFOPEN(3tiff)
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