tiff

Documentation

Overview

Package tiff implements TIFF decoding as defined in TIFF 6.0 specification.

Index

• type Dir
  • func DecodeDir(r ReadAtReader, order binary.ByteOrder) (d *Dir, offset int32, err error)
  • func (d *Dir) String() string
• type FormatType
• type ReadAtReader
• type Tag
  • func DecodeTag(r ReadAtReader, order binary.ByteOrder) (*Tag, error)
  • func (t *Tag) Float(i int) float64
  • func (t *Tag) Format() FormatType
  • func (t *Tag) Int(i int) int64
  • func (t *Tag) MarshalJSON() ([]byte, error)
  • func (t *Tag) Rat(i int) *big.Rat
  • func (t *Tag) Rat2(i int) (num, den int64)
  • func (t *Tag) String() string
  • func (t *Tag) StringVal() string
• type Tiff
  • func Decode(r io.Reader) (*Tiff, error)
  • func (tf *Tiff) String() string

Types

type Dir

type Dir struct {
	Tags []*Tag
}

Dir reflects the parsed content of a tiff Image File Directory (IFD).

func DecodeDir

func DecodeDir(r ReadAtReader, order binary.ByteOrder) (d *Dir, offset int32, err error)

DecodeDir parses a tiff-encoded IFD from r and returns a Dir object. offset is the offset to the next IFD. The first read from r should be at the first byte of the IFD. ReadAt offsets should be relative to the beginning of the tiff structure (not relative to the beginning of the IFD).

func (*Dir) String

func (d *Dir) String() string

type FormatType

type FormatType int

const (
	IntVal FormatType = iota
	FloatVal
	RatVal
	StringVal
	UndefVal
	OtherVal
)

type ReadAtReader

type ReadAtReader interface {
	io.Reader
	io.ReaderAt
}

ReadAtReader is used when decoding Tiff tags and directories

type Tag

type Tag struct {
	// Id is the 2-byte tiff tag identifier
	Id uint16
	// Fmt is an integer (1 through 12) indicating the tag value's format.
	Fmt uint16
	// Ncomp is the number of type Fmt stored in the tag's value (i.e. the tag's
	// value is an array of type Fmt and length Ncomp).
	Ncomp uint32
	// Val holds the bytes that represent the tag's value.
	Val []byte
	// contains filtered or unexported fields
}

Tag reflects the parsed content of a tiff IFD tag.

func DecodeTag

func DecodeTag(r ReadAtReader, order binary.ByteOrder) (*Tag, error)

DecodeTag parses a tiff-encoded IFD tag from r and returns Tag object. The first read from r should be the first byte of the tag. ReadAt offsets should be relative to the beginning of the tiff structure (not relative to the beginning of the tag).

func (*Tag) Float

func (t *Tag) Float(i int) float64

Float returns the tag's i'th value as a float. It panics if the tag format is not FloatVal or if the tag value has no i'th component.

func (*Tag) Format

func (t *Tag) Format() FormatType

Format returns a value indicating which method can be called to retrieve the tag's value properly typed (e.g. integer, rational, etc.).

func (*Tag) Int

func (t *Tag) Int(i int) int64

Int returns the tag's i'th value as an integer. It panics if the tag format is not IntVal or if the tag value has no i'th component.

func (*Tag) MarshalJSON

func (t *Tag) MarshalJSON() ([]byte, error)

func (*Tag) Rat

func (t *Tag) Rat(i int) *big.Rat

Rat returns the tag's i'th value as a rational number. It panics if the tag format is not RatVal, if the denominator is zero, or if the tag has no i'th component. If a denominator could be zero, use Rat2.

func (*Tag) Rat2

func (t *Tag) Rat2(i int) (num, den int64)

Rat2 returns the tag's i'th value as a rational number represented by a numerator-denominator pair. It panics if the tag format is not RatVal or if the tag value has no i'th component.

func (*Tag) String

func (t *Tag) String() string

String returns a nicely formatted version of the tag.

func (*Tag) StringVal

func (t *Tag) StringVal() string

StringVal returns the tag's value as a string. It panics if the tag format is not StringVal

type Tiff

type Tiff struct {
	// Dirs is an ordered slice of the tiff's Image File Directories (IFDs).
	// The IFD at index 0 is IFD0.
	Dirs []*Dir
	// The tiff's byte-encoding (i.e. big/little endian).
	Order binary.ByteOrder
}

Tiff provides access to decoded tiff data.

func Decode

func Decode(r io.Reader) (*Tiff, error)

Decode parses tiff-encoded data from r and returns a Tiff that reflects the structure and content of the tiff data. The first read from r should be the first byte of the tiff-encoded data (not necessarily the first byte of an os.File object).

func (*Tiff) String

func (tf *Tiff) String() string