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<title>TIFFOpen</title>

TIFFOpen

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

BYTE ORDER

RETURN VALUES

DIAGNOSTICS

SEE ALSO

NAME

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TIFFOpen, TIFFFdOpen, TIFFClientOpen − open a

<small>TIFF</small> file for reading or writing

SYNOPSIS

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#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

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TIFFOpen opens a <small>TIFF</small> 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

<small>TIFF</small> 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 <small>TIFF</small> 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 <small>TIFF</small> 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 <small>UNIX</small> -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

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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.

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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

<small>CPU</small> 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

<small>CPU</small> byte order.

L

Force image data that is read or written to be treated

with bits filled from Least Significant Bit (

<small>LSB</small> ) to Most Significant Bit (

<small>MSB</small> ). 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 (

<small>MSB</small> ) to Least Significant Bit (

<small>LSB</small> ); 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

<small>CPU.</small>

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

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The <small>TIFF</small> 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 <small>TIFF</small> images is incapable of reading images

in anything but the native <small>CPU</small> 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 <small>CPU</small> 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

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Upon successful completion TIFFOpen,

TIFFFdOpen, and TIFFClientOpen return a

<small>TIFF</small> pointer. Otherwise, NULL is

returned.

DIAGNOSTICS

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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

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libtiff(3TIFF), TIFFClose(3TIFF)