TIFFOpen(3tiff)
TIFFOpen(3TIFF) MISC. REFERENCE MANUAL PAGES TIFFOpen(3TIFF)
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
DESCRIPTION
TIFFOpen opens a TIFF file whose name is filename and
returns a handle to be used in subsequent calls to routines
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 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(3TIFF) for reading directories other than
the first). If a file is opened for writing or appending, a
default directory is automatically created for writing sub-
sequent data. This directory has all the default values
specified in TIFF Revision 6.0: BitsPerSample=1,
ThreshHolding=bilevel art scan, FillOrder=1 (most signifi-
cant 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), Sam-
plesPerPixel=1, RowsPerStrip=infinity, ResolutionUnit=2
(inches), and Compression=1 (no compression). To alter
these values, or to define values for additional fields,
TIFFSetField(3TIFF) must be used.
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TIFFOpen(3TIFF) MISC. REFERENCE MANUAL PAGES TIFFOpen(3TIFF)
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 asso-
ciated with the file descriptor must support random access.
TIFFClientOpen is like TIFFOpen except that the caller sup-
plies 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 TIFFClientOpen.
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 specifi-
cation.
l When creating a new file force information be written
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 written
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
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TIFFOpen(3TIFF) MISC. REFERENCE MANUAL PAGES TIFFOpen(3TIFF)
reading information. By default the library will
attempt to use memory-mapped files.
m Disable the use of memory-mapped files.
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 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 default
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.
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 sup-
port 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 appli-
cations 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 TIFFError(3TIFF)
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TIFFOpen(3TIFF) MISC. REFERENCE MANUAL PAGES TIFFOpen(3TIFF)
routine. Likewise, warning messages are directed to the
TIFFWarning(3TIFF) 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.
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 order-
ing of the current machine was opened for appending (``a'').
This is a limitation of the library.
SEE ALSO
libtiff(3TIFF), TIFFClose(3TIFF)
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