Tribblix: manual page: TIFFOpen.3tiff

TIFFOpen(3TIFF) 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, 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.

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 loading will be done in its entirety unless the O
flag is also specified.

O On-demand loading of values of the strip/tile offset/bytecount
arrays, 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 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.