TIFFOpen(3T) Image Format Library C++ Reference Manual 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 tsizet (*TIFFReadWriteProc)(thandlet, tdatat, tsizet);
typedef tofft (*TIFFSeekProc)(thandlet, tofft, int);
typedef int (*TIFFCloseProc)(thandlet);
typedef tofft (*TIFFSizeProc)(thandlet);
typedef int (*TIFFMapFileProc)(thandlet, tdatat*, tofft*);
typedef void (*TIFFUnmapFileProc)(thandlet, tdatat, tofft);
TIFF* TIFFClientOpen(const char* filename, const char* mode, thandlet clientdata,
TIFFReadWriteProc readproc, TIFFReadWriteProc writeproc, TIFFSeekProc seekproc,
TIFFCloseProc closeproc, TIFFSizeProc sizeproc, TIFFMapFileProc mapproc,
TIFFUnmapFileProc unmapproc)
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(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, 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=infinity, ResolutionUnit=2 (inches), and Compression=1 (no
compression). To alter these values, or to define values for additional
fields, TIFFSetField(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.
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TIFFOpen(3T) Image Format Library C++ Reference Manual 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 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 specification.
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
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 [-tile] image to multiple strips [tiles],
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 [tile] in its
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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 [tiles]. Finally, note that strip chopping is an optional
compile-time feature of the library; just because its use is enabled
by an application does not mean that it may be present in the
library.
c Disable the use of strip chopping when reading images.
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 TIFFError(3T) routine. 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 specified 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).
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TIFFOpen(3T) Image Format Library C++ Reference Manual TIFFOpen(3T)
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 ALSO
libtiff(3T), TIFFClose(3T)
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