tiff

package
v0.0.0-...-49a09c6 Latest Latest
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 Go to latest Published: May 20, 2014 License: BSD-2-Clause Imports: 6 Imported by: 0

Documentation

Overview

Package tiff provides support for decoding the structure of TIFF 6.0 files.

The specification can be found at http://www.exif.org/TIFF6.pdf.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type Ascii 

type Ascii uint8

type Byte 

type Byte uint8

type ByteOrder 

type ByteOrder struct {
	binary.ByteOrder
}

A ByteOrder represents the byte order of a TIFF file and supports decoding of the various TIFF types.

func (ByteOrder) Long 

func (order ByteOrder) Long(b []byte) Long

Read and decode 4 bytes as Long

func (ByteOrder) Offset 

func (order ByteOrder) Offset(b []byte) int64

Read a 4-byte file offset

func (ByteOrder) Rational 

func (order ByteOrder) Rational(b []byte) (r Rational)

Read and decode 2x 2-bytes as a Rational

func (ByteOrder) ReadIFD 

func (order ByteOrder) ReadIFD(r io.ReaderAt, offset int64) *IFD

func (ByteOrder) Short 

func (order ByteOrder) Short(b []byte) Short

Read and decode 2 bytes as Short

func (ByteOrder) Slong 

func (order ByteOrder) Slong(b []byte) Slong

func (ByteOrder) Srational 

func (order ByteOrder) Srational(b []byte) (r Srational)

Read and decode 2x 2-byte as a Srational

type Double 

type Double float64

type Entry 

type Entry struct {
	Offset int64    // Offset of this Entry within its associated ReaderAt
	Tag    TagID    // Tag code
	Type   TagType  // Tag type
	Count  TagCount // How many elements of type Type are covered by this Entry
	Value  TagValue // Value or offset to value if it doesn't fit in 4 bytes
}

An Entry contains the data for a single entry or field in an IFD (Image Field Directory).

func (Entry) ValueByteSize 

func (e Entry) ValueByteSize() int64

ValueByteSize returns the total byte size of e.Entry's Value.

func (Entry) ValueIsOffset 

func (e Entry) ValueIsOffset() bool

Returns true if e.Value is an offset to where the value data can be found.

type File 

type File struct {
	*Header
	io.ReaderAt
	IFD *IFD
}

A File represents a decoded TIFF file.

func Read 

func Read(r io.ReaderAt) (*File, error)

Read attempts to decode the provided io.ReaderAt according to the TIFF spec.

func (File) Bytes 

func (f File) Bytes(e Entry) ([]byte, error)

Bytes returns the Value bytes pointed to by a particular entry.

func (File) EntryReader 

func (f File) EntryReader(e Entry) io.ReaderAt

EntryReader returns a ReaderAt which can be used to extract the bytes associated with an Entry.

func (File) ReadIFD 

func (f File) ReadIFD(offset int64) *IFD

ReadIFD decodes the IFD structure of the File recursively until no more IFD's can be found.

type Float 

type Float float32
type Header struct {
	ByteOrder
	FirstIFD int64 // Offset to first IFD
}

Header represents a TIFF file header.

type IFD 

type IFD struct {
	Offset  int64
	Entries []Entry
	Next    *IFD
}

IFD describes the contents of an Image File Directory entry in a TIFF file.

type Long 

type Long uint32

type Rational 

type Rational struct {
	Numer, Denom Long
}

func (Rational) String 

func (r Rational) String() string

type Sbyte 

type Sbyte int8

type Short 

type Short uint16

type Slong 

type Slong int32

type Srational 

type Srational struct {
	Numer, Denom Slong
}

func (Srational) String 

func (r Srational) String() string

type Sshort 

type Sshort int16

type TagCount 

type TagCount uint32

A TagCount describes how many repeated elements there are of e.Type in this Entry.

type TagID 

type TagID uint16

A TagID represents the 16 bit integer identifier for an IFD tag.

func (TagID) GoString 

func (c TagID) GoString() string

Returns the TagID integer value encoded as a hexadecimal.

func (TagID) Lookup 

func (c TagID) Lookup(spaces ...TagSpace) string

Return the first name assocated with the TagID in the given TagSpace(s).

func (TagID) String 

func (c TagID) String() string

Returns the TagID name as defined in BaseLine, Extension, Private, Exif, and Gps TagSpaces.

type TagSpace 

type TagSpace struct {
	// contains filtered or unexported fields
}

A TagSpace represents a (named) collection of TIFF tags. 

var BaseLine TagSpace = CreateTagSpace("BaseLine")
var Exif TagSpace = CreateTagSpace("Exif")
var Extension TagSpace = CreateTagSpace("Extension")
var Gps TagSpace = CreateTagSpace("Gps")
var Private TagSpace = CreateTagSpace("Private")

func CreateTagSpace 

func CreateTagSpace(name string) TagSpace

CreateTagSpace returns a new TagSpace labelled name.

func (TagSpace) GetCode 

func (ns TagSpace) GetCode(name string) (TagID, error)

func (TagSpace) GetName 

func (ns TagSpace) GetName(c TagID) (string, error)

func (TagSpace) HasCode 

func (ns TagSpace) HasCode(c TagID) bool

Returns true if c is in ns.

func (TagSpace) HasName 

func (ns TagSpace) HasName(name string) bool

func (TagSpace) Set 

func (ns TagSpace) Set(code TagID, name string)

Set associates code and name in the TagSpace ns.

type TagType 

type TagType uint16

A TagType represents the 16 bit code for the different tag types defined by the TIFF spec. 

const (
	BYTE TagType = iota
	ASCII
	SHORT
	LONG
	RATIONAL
	SBYTE
	UNDEFINED
	SSHORT
	SLONG
	SRATIONAL
	FLOAT
	DOUBLE
	IFDPTR
)

func (TagType) ByteSize 

func (t TagType) ByteSize() int64

func (TagType) String 

func (t TagType) String() string

type TagValue 

type TagValue [4]byte

A TagValue contains the direct value stored in each TIFF entry.

type Undefined 

type Undefined uint8

Source Files

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