|
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.
|