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)
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 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(3TIFF) 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.
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 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 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(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 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).
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(3TIFF),
TIFFClose(3TIFF)