go-exif: github.com/dsoprea/go-exif/v3 Index | Examples | Files | Directories

package exif

import "github.com/dsoprea/go-exif/v3"

Package exif parses raw EXIF information given a block of raw EXIF data. It can also construct new EXIF information, and provides tools for doing so. This package is not involved with the parsing of particular file-formats.

The EXIF data must first be extracted and then provided to us. Conversely, when constructing new EXIF data, the caller is responsible for packaging this in whichever format they require.

Index

Examples

Package Files

data_layer.go error.go exif.go gps.go ifd_builder.go ifd_builder_encode.go ifd_enumerate.go ifd_tag_entry.go package.go tags.go tags_data.go testing_common.go utility.go

Constants

const (
    // ExifAddressableAreaStart is the absolute offset in the file that all
    // offsets are relative to.
    ExifAddressableAreaStart = uint32(0x0)

    // ExifDefaultFirstIfdOffset is essentially the number of bytes in addition
    // to `ExifAddressableAreaStart` that you have to move in order to escape
    // the rest of the header and get to the earliest point where we can put
    // stuff (which has to be the first IFD). This is the size of the header
    // sequence containing the two-character byte-order, two-character fixed-
    // bytes, and the four bytes describing the first-IFD offset.
    ExifDefaultFirstIfdOffset = uint32(2 + 2 + 4)
)
const (

    // ThumbnailFqIfdPath is the fully-qualified IFD path that the thumbnail
    // must be found in.
    ThumbnailFqIfdPath = "IFD1"

    // ThumbnailOffsetTagId returns the tag-ID of the thumbnail offset.
    ThumbnailOffsetTagId = 0x0201

    // ThumbnailSizeTagId returns the tag-ID of the thumbnail size.
    ThumbnailSizeTagId = 0x0202
)
const (

    // TagGpsVersionId is the ID of the GPS version tag.
    TagGpsVersionId = 0x0000

    // TagLatitudeId is the ID of the GPS latitude tag.
    TagLatitudeId = 0x0002

    // TagLatitudeRefId is the ID of the GPS latitude orientation tag.
    TagLatitudeRefId = 0x0001

    // TagLongitudeId is the ID of the GPS longitude tag.
    TagLongitudeId = 0x0004

    // TagLongitudeRefId is the ID of the GPS longitude-orientation tag.
    TagLongitudeRefId = 0x0003

    // TagTimestampId is the ID of the GPS time tag.
    TagTimestampId = 0x0007

    // TagDatestampId is the ID of the GPS date tag.
    TagDatestampId = 0x001d

    // TagAltitudeId is the ID of the GPS altitude tag.
    TagAltitudeId = 0x0006

    // TagAltitudeRefId is the ID of the GPS altitude-orientation tag.
    TagAltitudeRefId = 0x0005
)
const (
    // ExifSignatureLength is the number of bytes in the EXIF signature (which
    // customarily includes the first IFD offset).
    ExifSignatureLength = 8
)
const (
    // Tag-ID + Tag-Type + Unit-Count + Value/Offset.
    IfdTagEntrySize = uint32(2 + 2 + 4 + 4)
)

Variables

var (
    // ErrTagNotFound indicates that the tag was not found.
    ErrTagNotFound = errors.New("tag not found")

    // ErrTagNotKnown indicates that the tag is not registered with us as a
    // known tag.
    ErrTagNotKnown = errors.New("tag is not known")
)
var (
    ExifBigEndianSignature    = [4]byte{'M', 'M', 0x00, 0x2a}
    ExifLittleEndianSignature = [4]byte{'I', 'I', 0x2a, 0x00}
)
var (
    ErrNoExif          = errors.New("no exif data")
    ErrExifHeaderError = errors.New("exif header error")
)
var (
    ErrTagEntryNotFound = errors.New("tag entry not found")
    ErrChildIbNotFound  = errors.New("child IB not found")
)
var (
    // ErrNoThumbnail means that no thumbnail was found.
    ErrNoThumbnail = errors.New("no thumbnail")

    // ErrNoGpsTags means that no GPS info was found.
    ErrNoGpsTags = errors.New("no gps tags")

    // ErrTagTypeNotValid means that the tag-type is not valid.
    ErrTagTypeNotValid = errors.New("tag type invalid")

    // ErrOffsetInvalid means that the file offset is not valid.
    ErrOffsetInvalid = errors.New("file offset invalid")
)
var (
    // ErrGpsCoordinatesNotValid means that some part of the geographic data was
    // unparseable.
    ErrGpsCoordinatesNotValid = errors.New("GPS coordinates not valid")
)
var (
    // ValidGpsVersions is the list of recognized EXIF GPS versions/signatures.
    ValidGpsVersions = [][4]byte{

        {2, 0, 0, 0},

        {2, 2, 0, 0},

        {2, 3, 0, 0},
    }
)

func BuildExifHeader Uses

func BuildExifHeader(byteOrder binary.ByteOrder, firstIfdOffset uint32) (headerBytes []byte, err error)

BuildExifHeader constructs the bytes that go at the front of the stream.

Code:

headerBytes, err := BuildExifHeader(exifcommon.TestDefaultByteOrder, 0x11223344)
log.PanicIf(err)

eh, err := ParseExifHeader(headerBytes)
log.PanicIf(err)

fmt.Printf("%v\n", eh)

Output:

ExifHeader<BYTE-ORDER=[BigEndian] FIRST-IFD-OFFSET=(0x11223344)>

func Collect Uses

func Collect(ifdMapping *exifcommon.IfdMapping, tagIndex *TagIndex, exifData []byte) (eh ExifHeader, index IfdIndex, err error)

Collect recursively builds a static structure of all IFDs and tags.

func GetFlatExifData Uses

func GetFlatExifData(exifData []byte, so *ScanOptions) (exifTags []ExifTag, med *MiscellaneousExifData, err error)

GetFlatExifData returns a simple, flat representation of all tags.

func GpsDegreesEquals Uses

func GpsDegreesEquals(gi1, gi2 GpsDegrees) bool

GpsDegreesEquals returns true if the two `GpsDegrees` are identical.

func LoadStandardTags Uses

func LoadStandardTags(ti *TagIndex) (err error)

LoadStandardTags registers the tags that all devices/applications should support.

func SearchAndExtractExif Uses

func SearchAndExtractExif(data []byte) (rawExif []byte, err error)

SearchAndExtractExif searches for an EXIF blob in the byte-slice.

func SearchAndExtractExifWithReader Uses

func SearchAndExtractExifWithReader(r io.Reader) (rawExif []byte, err error)

SearchAndExtractExifWithReader searches for an EXIF blob using an `io.Reader`. We can't know how much long the EXIF data is without parsing it, so this will likely grab up a lot of the image-data, too.

func SearchFileAndExtractExif Uses

func SearchFileAndExtractExif(filepath string) (rawExif []byte, err error)

SearchFileAndExtractExif returns a slice from the beginning of the EXIF data to the end of the file (it's not practical to try and calculate where the data actually ends).

type BuilderTag Uses

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

func NewBuilderTag Uses

func NewBuilderTag(ifdPath string, tagId uint16, typeId exifcommon.TagTypePrimitive, value *IfdBuilderTagValue, byteOrder binary.ByteOrder) *BuilderTag

func NewChildIfdBuilderTag Uses

func NewChildIfdBuilderTag(ifdPath string, tagId uint16, value *IfdBuilderTagValue) *BuilderTag

func NewStandardBuilderTag Uses

func NewStandardBuilderTag(ifdPath string, it *IndexedTag, byteOrder binary.ByteOrder, value interface{}) *BuilderTag

NewStandardBuilderTag constructs a `BuilderTag` instance. The type is looked up. `ii` is the type of IFD that owns this tag.

func (*BuilderTag) SetValue Uses

func (bt *BuilderTag) SetValue(byteOrder binary.ByteOrder, value interface{}) (err error)

Code:

testImageFilepath := getTestImageFilepath()

rawExif, err := SearchFileAndExtractExif(testImageFilepath)
log.PanicIf(err)

im, err := exifcommon.NewIfdMappingWithStandard()
log.PanicIf(err)

ti := NewTagIndex()

_, index, err := Collect(im, ti, rawExif)
log.PanicIf(err)

// Create builder.

rootIb := NewIfdBuilderFromExistingChain(index.RootIfd)

// Find tag to update.

exifBt, err := rootIb.FindTagWithName("ExifTag")
log.PanicIf(err)

ucBt, err := exifBt.value.Ib().FindTagWithName("UserComment")
log.PanicIf(err)

// Update the value. Since this is an "undefined"-type tag, we have to use
// its type-specific struct.

// TODO(dustin): !! Add an example for setting a non-unknown value, too.
uc := exifundefined.Tag9286UserComment{
    EncodingType:  exifundefined.TagUndefinedType_9286_UserComment_Encoding_ASCII,
    EncodingBytes: []byte("TEST COMMENT"),
}

err = ucBt.SetValue(rootIb.byteOrder, uc)
log.PanicIf(err)

// Encode.

ibe := NewIfdByteEncoder()

// This returns the raw bytes that you will be looking for, but there's no
// use for them at this point in the example.
_, err = ibe.EncodeToExif(rootIb)
log.PanicIf(err)

func (*BuilderTag) String Uses

func (bt *BuilderTag) String() string

func (*BuilderTag) Value Uses

func (bt *BuilderTag) Value() (value *IfdBuilderTagValue)

type ByteWriter Uses

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

func NewByteWriter Uses

func NewByteWriter(b *bytes.Buffer, byteOrder binary.ByteOrder) (bw *ByteWriter)

func (ByteWriter) WriteFourBytes Uses

func (bw ByteWriter) WriteFourBytes(value []byte) (err error)

func (ByteWriter) WriteUint16 Uses

func (bw ByteWriter) WriteUint16(value uint16) (err error)

func (ByteWriter) WriteUint32 Uses

func (bw ByteWriter) WriteUint32(value uint32) (err error)

type ExifBlobSeeker Uses

type ExifBlobSeeker interface {
    GetReadSeeker(initialOffset int64) (rs io.ReadSeeker, err error)
}

type ExifHeader Uses

type ExifHeader struct {
    ByteOrder      binary.ByteOrder
    FirstIfdOffset uint32
}

func ParseExifHeader Uses

func ParseExifHeader(data []byte) (eh ExifHeader, err error)

ParseExifHeader parses the bytes at the very top of the header.

This will panic with ErrNoExif on any data errors so that we can double as an EXIF-detection routine.

func Visit Uses

func Visit(rootIfdIdentity *exifcommon.IfdIdentity, ifdMapping *exifcommon.IfdMapping, tagIndex *TagIndex, exifData []byte, visitor TagVisitorFn, so *ScanOptions) (eh ExifHeader, furthestOffset uint32, err error)

Visit recursively invokes a callback for every tag.

func (ExifHeader) String Uses

func (eh ExifHeader) String() string

type ExifReadSeeker Uses

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

ExifReadSeeker knows how to retrieve data from the EXIF blob relative to the beginning of the blob (so, absolute position (0) is the first byte of the EXIF data).

func NewExifReadSeeker Uses

func NewExifReadSeeker(rs io.ReadSeeker) *ExifReadSeeker

func NewExifReadSeekerWithBytes Uses

func NewExifReadSeekerWithBytes(exifData []byte) *ExifReadSeeker

func (*ExifReadSeeker) GetReadSeeker Uses

func (edbs *ExifReadSeeker) GetReadSeeker(initialOffset int64) (rs io.ReadSeeker, err error)

Fork creates a new ReadSeeker instead that wraps a BouncebackReader to maintain its own position in the stream.

type ExifTag Uses

type ExifTag struct {
    // IfdPath is the fully-qualified IFD path (even though it is not named as
    // such).
    IfdPath string `json:"ifd_path"`

    // TagId is the tag-ID.
    TagId uint16 `json:"id"`

    // TagName is the tag-name. This is never empty.
    TagName string `json:"name"`

    // UnitCount is the recorded number of units constution of the value.
    UnitCount uint32 `json:"unit_count"`

    // TagTypeId is the type-ID.
    TagTypeId exifcommon.TagTypePrimitive `json:"type_id"`

    // TagTypeName is the type name.
    TagTypeName string `json:"type_name"`

    // Value is the decoded value.
    Value interface{} `json:"value"`

    // ValueBytes is the raw, encoded value.
    ValueBytes []byte `json:"value_bytes"`

    // Formatted is the human representation of the first value (tag values are
    // always an array).
    FormattedFirst string `json:"formatted_first"`

    // Formatted is the human representation of the complete value.
    Formatted string `json:"formatted"`

    // ChildIfdPath is the name of the child IFD this tag represents (if it
    // represents any). Otherwise, this is empty.
    ChildIfdPath string `json:"child_ifd_path"`
}

ExifTag is one simple representation of a tag in a flat list of all of them.

func (ExifTag) String Uses

func (et ExifTag) String() string

String returns a string representation.

type GpsDegrees Uses

type GpsDegrees struct {
    // Orientation describes the N/E/S/W direction that this position is
    // relative to.
    Orientation byte

    // Degrees is a simple float representing the underlying rational degrees
    // amount.
    Degrees float64

    // Minutes is a simple float representing the underlying rational minutes
    // amount.
    Minutes float64

    // Seconds is a simple float representing the underlying ration seconds
    // amount.
    Seconds float64
}

GpsDegrees is a high-level struct representing geographic data.

func NewGpsDegreesFromRationals Uses

func NewGpsDegreesFromRationals(refValue string, rawCoordinate []exifcommon.Rational) (gd GpsDegrees, err error)

NewGpsDegreesFromRationals returns a GpsDegrees struct given the EXIF-encoded information. The refValue is the N/E/S/W direction that this position is relative to.

func (GpsDegrees) Decimal Uses

func (d GpsDegrees) Decimal() float64

Decimal calculates and returns the simplified float representation of the component degrees.

func (GpsDegrees) Raw Uses

func (d GpsDegrees) Raw() []exifcommon.Rational

Raw returns a Rational struct that can be used to *write* coordinates. In practice, the denominator are typically (1) in the original EXIF data, and, that being the case, this will best preserve precision.

func (GpsDegrees) String Uses

func (d GpsDegrees) String() string

String provides returns a descriptive string.

type GpsInfo Uses

type GpsInfo struct {
    Latitude, Longitude GpsDegrees
    Altitude            int
    Timestamp           time.Time
}

GpsInfo encapsulates all of the geographic information in one place.

func (*GpsInfo) S2CellId Uses

func (gi *GpsInfo) S2CellId() s2.CellID

S2CellId returns the cell-ID of the geographic location on the earth.

func (*GpsInfo) String Uses

func (gi *GpsInfo) String() string

String returns a descriptive string.

type Ifd Uses

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

Ifd represents a single, parsed IFD.

func FindIfdFromRootIfd Uses

func FindIfdFromRootIfd(rootIfd *Ifd, ifdPath string) (ifd *Ifd, err error)

FindIfdFromRootIfd returns the given `Ifd` given the root-IFD and path of the desired IFD.

func (*Ifd) ByteOrder Uses

func (ifd *Ifd) ByteOrder() binary.ByteOrder

Offset returns the offset of the IFD in the stream.

func (*Ifd) ChildIfdIndex Uses

func (ifd *Ifd) ChildIfdIndex() map[string]*Ifd

ChildWithIfdPath returns a map of all child IFDs of this IFD.

func (*Ifd) ChildWithIfdPath Uses

func (ifd *Ifd) ChildWithIfdPath(iiChild *exifcommon.IfdIdentity) (childIfd *Ifd, err error)

ChildWithIfdPath returns an `Ifd` struct for the given child of the current IFD.

func (*Ifd) Children Uses

func (ifd *Ifd) Children() []*Ifd

Children returns a flat list of all child IFDs of this IFD.

func (*Ifd) DumpTags Uses

func (ifd *Ifd) DumpTags() []*IfdTagEntry

DumpTags prints the IFD hierarchy.

func (*Ifd) DumpTree Uses

func (ifd *Ifd) DumpTree() []string

DumpTree returns a list of strings describing the IFD hierarchy.

func (*Ifd) Entries Uses

func (ifd *Ifd) Entries() []*IfdTagEntry

Entries returns a flat list of all tags for this IFD.

func (*Ifd) EntriesByTagId Uses

func (ifd *Ifd) EntriesByTagId() map[uint16][]*IfdTagEntry

EntriesByTagId returns a map of all tags for this IFD.

func (*Ifd) EnumerateTagsRecursively Uses

func (ifd *Ifd) EnumerateTagsRecursively(visitor ParsedTagVisitor) (err error)

EnumerateTagsRecursively calls the given visitor function for every tag and IFD in the current IFD, recursively.

Code:

testImageFilepath := getTestImageFilepath()

rawExif, err := SearchFileAndExtractExif(testImageFilepath)
log.PanicIf(err)

im, err := exifcommon.NewIfdMappingWithStandard()
log.PanicIf(err)

ti := NewTagIndex()

_, index, err := Collect(im, ti, rawExif)
log.PanicIf(err)

cb := func(ifd *Ifd, ite *IfdTagEntry) error {

    // Something useful.

    return nil
}

err = index.RootIfd.EnumerateTagsRecursively(cb)
log.PanicIf(err)

func (*Ifd) FindTagWithId Uses

func (ifd *Ifd) FindTagWithId(tagId uint16) (results []*IfdTagEntry, err error)

FindTagWithId returns a list of tags (usually just zero or one) that match the given tag ID. This is efficient.

func (*Ifd) FindTagWithName Uses

func (ifd *Ifd) FindTagWithName(tagName string) (results []*IfdTagEntry, err error)

FindTagWithName returns a list of tags (usually just zero or one) that match the given tag name. This is not efficient (though the labor is trivial).

Code:

testImageFilepath := getTestImageFilepath()

rawExif, err := SearchFileAndExtractExif(testImageFilepath)
log.PanicIf(err)

im, err := exifcommon.NewIfdMappingWithStandard()
log.PanicIf(err)

ti := NewTagIndex()

_, index, err := Collect(im, ti, rawExif)
log.PanicIf(err)

tagName := "Model"

rootIfd := index.RootIfd

// We know the tag we want is on IFD0 (the first/root IFD).
results, err := rootIfd.FindTagWithName(tagName)
log.PanicIf(err)

// This should never happen.
if len(results) != 1 {
    log.Panicf("there wasn't exactly one result")
}

ite := results[0]

valueRaw, err := ite.Value()
log.PanicIf(err)

value := valueRaw.(string)
fmt.Println(value)

Output:

Canon EOS 5D Mark III

func (*Ifd) GpsInfo Uses

func (ifd *Ifd) GpsInfo() (gi *GpsInfo, err error)

GpsInfo parses and consolidates the GPS info. This can only be called on the GPS IFD.

Code:

filepath := getTestGpsImageFilepath()

rawExif, err := SearchFileAndExtractExif(filepath)
log.PanicIf(err)

im, err := exifcommon.NewIfdMappingWithStandard()
log.PanicIf(err)

ti := NewTagIndex()

_, index, err := Collect(im, ti, rawExif)
log.PanicIf(err)

ifd, err := index.RootIfd.ChildWithIfdPath(exifcommon.IfdGpsInfoStandardIfdIdentity)
log.PanicIf(err)

gi, err := ifd.GpsInfo()
log.PanicIf(err)

fmt.Printf("%s\n", gi)

Output:

GpsInfo<LAT=(26.58667) LON=(-80.05361) ALT=(0) TIME=[2018-04-29 01:22:57 +0000 UTC]>

func (*Ifd) IfdIdentity Uses

func (ifd *Ifd) IfdIdentity() *exifcommon.IfdIdentity

IfdIdentity returns IFD identity that this struct represents.

func (*Ifd) NextIfd Uses

func (ifd *Ifd) NextIfd() *Ifd

NextIfd returns the Ifd struct for the next IFD in the chain.

func (*Ifd) Offset Uses

func (ifd *Ifd) Offset() uint32

Offset returns the offset of the IFD in the stream.

func (*Ifd) ParentTagIndex Uses

func (ifd *Ifd) ParentTagIndex() int

ParentTagIndex returns the position of this IFD's tag in its parent IFD (*if* there is a parent).

func (*Ifd) PrintIfdTree Uses

func (ifd *Ifd) PrintIfdTree()

PrintIfdTree prints the IFD hierarchy.

func (*Ifd) PrintTagTree Uses

func (ifd *Ifd) PrintTagTree(populateValues bool)

PrintTagTree prints the IFD hierarchy.

func (*Ifd) String Uses

func (ifd *Ifd) String() string

String returns a description string.

func (*Ifd) Thumbnail Uses

func (ifd *Ifd) Thumbnail() (data []byte, err error)

Thumbnail returns the raw thumbnail bytes. This is typically directly readable by any standard image viewer.

Code:

testImageFilepath := getTestImageFilepath()

rawExif, err := SearchFileAndExtractExif(testImageFilepath)
log.PanicIf(err)

im, err := exifcommon.NewIfdMappingWithStandard()
log.PanicIf(err)

ti := NewTagIndex()

_, index, err := Collect(im, ti, rawExif)
log.PanicIf(err)

// This returns the raw bytes that you will be looking for, but there's no
// use for them at this point in the example.
_, err = index.RootIfd.nextIfd.Thumbnail()
log.PanicIf(err)

type IfdBuilder Uses

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

func GetOrCreateIbFromRootIb Uses

func GetOrCreateIbFromRootIb(rootIb *IfdBuilder, fqIfdPath string) (ib *IfdBuilder, err error)

GetOrCreateIbFromRootIb returns an IB representing the requested IFD, even if an IB doesn't already exist for it. This function may call itself recursively.

func NewIfdBuilder Uses

func NewIfdBuilder(ifdMapping *exifcommon.IfdMapping, tagIndex *TagIndex, ii *exifcommon.IfdIdentity, byteOrder binary.ByteOrder) (ib *IfdBuilder)

func NewIfdBuilderFromExistingChain Uses

func NewIfdBuilderFromExistingChain(rootIfd *Ifd) (firstIb *IfdBuilder)

NewIfdBuilderFromExistingChain creates a chain of IB instances from an IFD chain generated from real data.

func NewIfdBuilderWithExistingIfd Uses

func NewIfdBuilderWithExistingIfd(ifd *Ifd) (ib *IfdBuilder)

NewIfdBuilderWithExistingIfd creates a new IB using the same header type information as the given IFD.

func (*IfdBuilder) Add Uses

func (ib *IfdBuilder) Add(bt *BuilderTag) (err error)

func (*IfdBuilder) AddChildIb Uses

func (ib *IfdBuilder) AddChildIb(childIb *IfdBuilder) (err error)

AddChildIb adds a tag that branches to a new IFD.

func (*IfdBuilder) AddStandard Uses

func (ib *IfdBuilder) AddStandard(tagId uint16, value interface{}) (err error)

AddStandard quickly and easily composes and adds the tag using the information already known about a tag. Only works with standard tags.

func (*IfdBuilder) AddStandardWithName Uses

func (ib *IfdBuilder) AddStandardWithName(tagName string, value interface{}) (err error)

AddStandardWithName quickly and easily composes and adds the tag using the information already known about a tag (using the name). Only works with standard tags.

func (*IfdBuilder) AddTagsFromExisting Uses

func (ib *IfdBuilder) AddTagsFromExisting(ifd *Ifd, includeTagIds []uint16, excludeTagIds []uint16) (err error)

AddTagsFromExisting does a verbatim copy of the entries in `ifd` to this builder. It excludes child IFDs. These must be added explicitly via `AddChildIb()`.

func (*IfdBuilder) ChildWithTagId Uses

func (ib *IfdBuilder) ChildWithTagId(childIfdTagId uint16) (childIb *IfdBuilder, err error)

func (*IfdBuilder) DeleteAll Uses

func (ib *IfdBuilder) DeleteAll(tagId uint16) (n int, err error)

func (*IfdBuilder) DeleteFirst Uses

func (ib *IfdBuilder) DeleteFirst(tagId uint16) (err error)

func (*IfdBuilder) DeleteN Uses

func (ib *IfdBuilder) DeleteN(tagId uint16, n int) (err error)

func (*IfdBuilder) DumpToStrings Uses

func (ib *IfdBuilder) DumpToStrings() (lines []string)

func (*IfdBuilder) Find Uses

func (ib *IfdBuilder) Find(tagId uint16) (position int, err error)

func (*IfdBuilder) FindN Uses

func (ib *IfdBuilder) FindN(tagId uint16, maxFound int) (found []int, err error)

func (*IfdBuilder) FindTag Uses

func (ib *IfdBuilder) FindTag(tagId uint16) (bt *BuilderTag, err error)

func (*IfdBuilder) FindTagWithName Uses

func (ib *IfdBuilder) FindTagWithName(tagName string) (bt *BuilderTag, err error)

func (*IfdBuilder) IfdIdentity Uses

func (ib *IfdBuilder) IfdIdentity() *exifcommon.IfdIdentity

func (*IfdBuilder) NewBuilderTagFromBuilder Uses

func (ib *IfdBuilder) NewBuilderTagFromBuilder(childIb *IfdBuilder) (bt *BuilderTag)

func (*IfdBuilder) NextIb Uses

func (ib *IfdBuilder) NextIb() (nextIb *IfdBuilder, err error)

func (*IfdBuilder) PrintIfdTree Uses

func (ib *IfdBuilder) PrintIfdTree()

func (*IfdBuilder) PrintTagTree Uses

func (ib *IfdBuilder) PrintTagTree()

func (*IfdBuilder) Replace Uses

func (ib *IfdBuilder) Replace(tagId uint16, bt *BuilderTag) (err error)

func (*IfdBuilder) ReplaceAt Uses

func (ib *IfdBuilder) ReplaceAt(position int, bt *BuilderTag) (err error)

func (*IfdBuilder) Set Uses

func (ib *IfdBuilder) Set(bt *BuilderTag) (err error)

Set will add a new entry or update an existing entry.

func (*IfdBuilder) SetNextIb Uses

func (ib *IfdBuilder) SetNextIb(nextIb *IfdBuilder) (err error)

func (*IfdBuilder) SetStandard Uses

func (ib *IfdBuilder) SetStandard(tagId uint16, value interface{}) (err error)

SetStandard quickly and easily composes and adds or replaces the tag using the information already known about a tag. Only works with standard tags.

func (*IfdBuilder) SetStandardWithName Uses

func (ib *IfdBuilder) SetStandardWithName(tagName string, value interface{}) (err error)

SetStandardWithName quickly and easily composes and adds or replaces the tag using the information already known about a tag (using the name). Only works with standard tags.

ExampleIfdBuilder_SetStandardWithName establishes a chain of `IfdBuilder` structs from an existing chain of `Ifd` structs, navigates to the IB representing IFD0, updates the ProcessingSoftware tag to a different value, encodes down to a new EXIF block, reparses, and validates that the value for that tag is what we set it to.

Code:

testImageFilepath := getTestImageFilepath()

rawExif, err := SearchFileAndExtractExif(testImageFilepath)
log.PanicIf(err)

// Boilerplate.

im, err := exifcommon.NewIfdMappingWithStandard()
log.PanicIf(err)

ti := NewTagIndex()

// Load current IFDs.

_, index, err := Collect(im, ti, rawExif)
log.PanicIf(err)

ib := NewIfdBuilderFromExistingChain(index.RootIfd)

// Read the IFD whose tag we want to change.

// Standard:
// - "IFD0"
// - "IFD0/Exif0"
// - "IFD0/Exif0/Iop0"
// - "IFD0/GPSInfo0"
//
// If the numeric indices are not included, (0) is the default. Note that
// this isn't strictly necessary in our case since IFD0 is the first IFD anyway, but we're putting it here to show usage.
ifdPath := "IFD0"

childIb, err := GetOrCreateIbFromRootIb(ib, ifdPath)
log.PanicIf(err)

// There are a few functions that allow you to surgically change the tags in an
// IFD, but we're just gonna overwrite a tag that has an ASCII value.

tagName := "ProcessingSoftware"

err = childIb.SetStandardWithName(tagName, "alternative software")
log.PanicIf(err)

// Encode the in-memory representation back down to bytes.

ibe := NewIfdByteEncoder()

updatedRawExif, err := ibe.EncodeToExif(ib)
log.PanicIf(err)

// Reparse the EXIF to confirm that our value is there.

_, index, err = Collect(im, ti, updatedRawExif)
log.PanicIf(err)

// This isn't strictly necessary for the same reason as above, but it's here
// for documentation.
childIfd, err := FindIfdFromRootIfd(index.RootIfd, ifdPath)
log.PanicIf(err)

results, err := childIfd.FindTagWithName(tagName)
log.PanicIf(err)

for _, ite := range results {
    valueRaw, err := ite.Value()
    log.PanicIf(err)

    stringValue := valueRaw.(string)
    fmt.Println(stringValue)
}

Output:

alternative software

Code:

// Check initial value.

filepath := getTestGpsImageFilepath()

rawExif, err := SearchFileAndExtractExif(filepath)
log.PanicIf(err)

im, err := exifcommon.NewIfdMappingWithStandard()
log.PanicIf(err)

ti := NewTagIndex()

_, index, err := Collect(im, ti, rawExif)
log.PanicIf(err)

rootIfd := index.RootIfd

// Update the value.

rootIb := NewIfdBuilderFromExistingChain(rootIfd)

exifIb, err := rootIb.ChildWithTagId(exifcommon.IfdExifStandardIfdIdentity.TagId())
log.PanicIf(err)

t := time.Date(2020, 06, 7, 1, 30, 0, 0, time.UTC)

err = exifIb.SetStandardWithName("DateTimeDigitized", t)
log.PanicIf(err)

// Encode to bytes.

ibe := NewIfdByteEncoder()

updatedRawExif, err := ibe.EncodeToExif(rootIb)
log.PanicIf(err)

// Decode from bytes.

_, updatedIndex, err := Collect(im, ti, updatedRawExif)
log.PanicIf(err)

updatedRootIfd := updatedIndex.RootIfd

// Test.

updatedExifIfd, err := updatedRootIfd.ChildWithIfdPath(exifcommon.IfdExifStandardIfdIdentity)
log.PanicIf(err)

results, err := updatedExifIfd.FindTagWithName("DateTimeDigitized")
log.PanicIf(err)

ite := results[0]

phrase, err := ite.FormatFirst()
log.PanicIf(err)

fmt.Printf("%s\n", phrase)

Output:

2020:06:07 01:30:00

Code:

// Check initial value.

filepath := getTestGpsImageFilepath()

rawExif, err := SearchFileAndExtractExif(filepath)
log.PanicIf(err)

im, err := exifcommon.NewIfdMappingWithStandard()
log.PanicIf(err)

ti := NewTagIndex()

_, index, err := Collect(im, ti, rawExif)
log.PanicIf(err)

rootIfd := index.RootIfd

gpsIfd, err := rootIfd.ChildWithIfdPath(exifcommon.IfdGpsInfoStandardIfdIdentity)
log.PanicIf(err)

initialGi, err := gpsIfd.GpsInfo()
log.PanicIf(err)

fmt.Printf("Original:\n%s\n\n", initialGi.Latitude.String())

// Update the value.

rootIb := NewIfdBuilderFromExistingChain(rootIfd)

gpsIb, err := rootIb.ChildWithTagId(exifcommon.IfdGpsInfoStandardIfdIdentity.TagId())
log.PanicIf(err)

updatedGi := GpsDegrees{
    Degrees: 11,
    Minutes: 22,
    Seconds: 33,
}

raw := updatedGi.Raw()

err = gpsIb.SetStandardWithName("GPSLatitude", raw)
log.PanicIf(err)

// Encode to bytes.

ibe := NewIfdByteEncoder()

updatedRawExif, err := ibe.EncodeToExif(rootIb)
log.PanicIf(err)

// Decode from bytes.

_, updatedIndex, err := Collect(im, ti, updatedRawExif)
log.PanicIf(err)

updatedRootIfd := updatedIndex.RootIfd

// Test.

updatedGpsIfd, err := updatedRootIfd.ChildWithIfdPath(exifcommon.IfdGpsInfoStandardIfdIdentity)
log.PanicIf(err)

recoveredUpdatedGi, err := updatedGpsIfd.GpsInfo()
log.PanicIf(err)

fmt.Printf("Updated, written, and re-read:\n%s\n", recoveredUpdatedGi.Latitude.String())

Output:

Original:
Degrees<O=[N] D=(26) M=(35) S=(12)>

Updated, written, and re-read:
Degrees<O=[N] D=(11) M=(22) S=(33)>

func (*IfdBuilder) SetThumbnail Uses

func (ib *IfdBuilder) SetThumbnail(data []byte) (err error)

SetThumbnail sets thumbnail data.

NOTES:

- We don't manage any facet of the thumbnail data. This is the

responsibility of the user/developer.

- This method will fail unless the thumbnail is set on a the root IFD.

However, in order to be valid, it must be set on the second one, linked to
by the first, as per the EXIF/TIFF specification.

- We set the offset to (0) now but will allocate the data and properly assign

the offset when the IB is encoded (later).

func (*IfdBuilder) String Uses

func (ib *IfdBuilder) String() string

func (*IfdBuilder) Tags Uses

func (ib *IfdBuilder) Tags() (tags []*BuilderTag)

func (*IfdBuilder) Thumbnail Uses

func (ib *IfdBuilder) Thumbnail() []byte

type IfdBuilderTagValue Uses

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

func NewIfdBuilderTagValueFromBytes Uses

func NewIfdBuilderTagValueFromBytes(valueBytes []byte) *IfdBuilderTagValue

func NewIfdBuilderTagValueFromIfdBuilder Uses

func NewIfdBuilderTagValueFromIfdBuilder(ib *IfdBuilder) *IfdBuilderTagValue

func (IfdBuilderTagValue) Bytes Uses

func (ibtv IfdBuilderTagValue) Bytes() []byte

func (IfdBuilderTagValue) Ib Uses

func (ibtv IfdBuilderTagValue) Ib() *IfdBuilder

func (IfdBuilderTagValue) IsBytes Uses

func (ibtv IfdBuilderTagValue) IsBytes() bool

IsBytes returns true if the bytes are populated. This is always the case when we're loaded from a tag in an existing IFD.

func (IfdBuilderTagValue) IsIb Uses

func (ibtv IfdBuilderTagValue) IsIb() bool

func (IfdBuilderTagValue) String Uses

func (ibtv IfdBuilderTagValue) String() string

type IfdByteEncoder Uses

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

IfdByteEncoder converts an IB to raw bytes (for writing) while also figuring out all of the allocations and indirection that is required for extended data.

func NewIfdByteEncoder Uses

func NewIfdByteEncoder() (ibe *IfdByteEncoder)

func (*IfdByteEncoder) EncodeToExif Uses

func (ibe *IfdByteEncoder) EncodeToExif(ib *IfdBuilder) (data []byte, err error)

EncodeToExif calls EncodeToExifPayload and then packages the result into a complete EXIF block.

Code:

// Construct an IFD.

im, err := exifcommon.NewIfdMappingWithStandard()
log.PanicIf(err)

ti := NewTagIndex()
ib := NewIfdBuilder(im, ti, exifcommon.IfdStandardIfdIdentity, exifcommon.TestDefaultByteOrder)

err = ib.AddStandardWithName("ProcessingSoftware", "asciivalue")
log.PanicIf(err)

err = ib.AddStandardWithName("DotRange", []uint8{0x11})
log.PanicIf(err)

err = ib.AddStandardWithName("SubfileType", []uint16{0x2233})
log.PanicIf(err)

err = ib.AddStandardWithName("ImageWidth", []uint32{0x44556677})
log.PanicIf(err)

err = ib.AddStandardWithName("WhitePoint", []exifcommon.Rational{{Numerator: 0x11112222, Denominator: 0x33334444}})
log.PanicIf(err)

err = ib.AddStandardWithName("ShutterSpeedValue", []exifcommon.SignedRational{{Numerator: 0x11112222, Denominator: 0x33334444}})
log.PanicIf(err)

// Encode it.

ibe := NewIfdByteEncoder()

exifData, err := ibe.EncodeToExif(ib)
log.PanicIf(err)

// Parse it so we can see it.

_, index, err := Collect(im, ti, exifData)
log.PanicIf(err)

for i, ite := range index.RootIfd.Entries() {
    value, err := ite.Value()
    log.PanicIf(err)

    fmt.Printf("%d: %s [%v]\n", i, ite, value)
}

Output:

0: IfdTagEntry<TAG-IFD-PATH=[IFD] TAG-ID=(0x000b) TAG-TYPE=[ASCII] UNIT-COUNT=(11)> [asciivalue]
1: IfdTagEntry<TAG-IFD-PATH=[IFD] TAG-ID=(0x0150) TAG-TYPE=[BYTE] UNIT-COUNT=(1)> [[17]]
2: IfdTagEntry<TAG-IFD-PATH=[IFD] TAG-ID=(0x00ff) TAG-TYPE=[SHORT] UNIT-COUNT=(1)> [[8755]]
3: IfdTagEntry<TAG-IFD-PATH=[IFD] TAG-ID=(0x0100) TAG-TYPE=[LONG] UNIT-COUNT=(1)> [[1146447479]]
4: IfdTagEntry<TAG-IFD-PATH=[IFD] TAG-ID=(0x013e) TAG-TYPE=[RATIONAL] UNIT-COUNT=(1)> [[{286335522 858997828}]]
5: IfdTagEntry<TAG-IFD-PATH=[IFD] TAG-ID=(0x9201) TAG-TYPE=[SRATIONAL] UNIT-COUNT=(1)> [[{286335522 858997828}]]

func (*IfdByteEncoder) EncodeToExifPayload Uses

func (ibe *IfdByteEncoder) EncodeToExifPayload(ib *IfdBuilder) (data []byte, err error)

EncodeToExifPayload is the base encoding step that transcribes the entire IB structure to its on-disk layout.

func (*IfdByteEncoder) Journal Uses

func (ibe *IfdByteEncoder) Journal() [][3]string

func (*IfdByteEncoder) PrintJournal Uses

func (ibe *IfdByteEncoder) PrintJournal()

PrintJournal prints a hierarchical representation of the steps taken during encoding.

func (*IfdByteEncoder) TableSize Uses

func (ibe *IfdByteEncoder) TableSize(entryCount int) uint32

type IfdEnumerate Uses

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

IfdEnumerate is the main enumeration type. It knows how to parse the IFD containers in the EXIF blob.

func NewIfdEnumerate Uses

func NewIfdEnumerate(ifdMapping *exifcommon.IfdMapping, tagIndex *TagIndex, ebs ExifBlobSeeker, byteOrder binary.ByteOrder) *IfdEnumerate

NewIfdEnumerate returns a new instance of IfdEnumerate.

func (*IfdEnumerate) Collect Uses

func (ie *IfdEnumerate) Collect(rootIfdOffset uint32) (index IfdIndex, err error)

Collect enumerates the different EXIF blocks (called IFDs) and builds out an index struct for referencing all of the parsed data.

func (*IfdEnumerate) FurthestOffset Uses

func (ie *IfdEnumerate) FurthestOffset() uint32

FurthestOffset returns the furthest offset visited in the EXIF blob. This *does not* account for the locations of any undefined tags since we always evaluate the furthest offset, whether or not the user wants to know it.

We are not willing to incur the cost of actually parsing those tags just to know their length when there are still undefined tags that are out there that we still won't have any idea how to parse, thus making this an approximation regardless of how clever we get.

func (*IfdEnumerate) Scan Uses

func (ie *IfdEnumerate) Scan(iiRoot *exifcommon.IfdIdentity, ifdOffset uint32, visitor TagVisitorFn, so *ScanOptions) (med *MiscellaneousExifData, err error)

Scan enumerates the different EXIF blocks (called IFDs). `rootIfdName` will be "IFD" in the TIFF standard.

type IfdIndex Uses

type IfdIndex struct {
    RootIfd *Ifd
    Ifds    []*Ifd
    Tree    map[int]*Ifd
    Lookup  map[string]*Ifd
}

IfdIndex collects a bunch of IFD and tag information stored in several different ways in order to provide convenient lookups.

type IfdTagEntry Uses

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

IfdTagEntry refers to a tag in the loaded EXIF block.

func (*IfdTagEntry) ChildFqIfdPath Uses

func (ite *IfdTagEntry) ChildFqIfdPath() string

ChildFqIfdPath returns the complete path of the child IFD along with the numeric suffixes differentiating sibling occurrences of the same type. "0" indices are omitted.

func (*IfdTagEntry) ChildIfdName Uses

func (ite *IfdTagEntry) ChildIfdName() string

ChildIfdName returns the name of the child IFD

func (*IfdTagEntry) ChildIfdPath Uses

func (ite *IfdTagEntry) ChildIfdPath() string

ChildIfdPath returns the path of the child IFD.

func (*IfdTagEntry) Format Uses

func (ite *IfdTagEntry) Format() (phrase string, err error)

Format returns the tag's value as a string.

func (*IfdTagEntry) FormatFirst Uses

func (ite *IfdTagEntry) FormatFirst() (phrase string, err error)

FormatFirst returns the same as Format() but only the first item.

func (*IfdTagEntry) GetRawBytes Uses

func (ite *IfdTagEntry) GetRawBytes() (rawBytes []byte, err error)

GetRawBytes renders a specific list of bytes from the value in this tag.

func (*IfdTagEntry) IfdIdentity Uses

func (ite *IfdTagEntry) IfdIdentity() *exifcommon.IfdIdentity

IfdIdentity returns the IfdIdentity associated with this tag.

func (*IfdTagEntry) IfdPath Uses

func (ite *IfdTagEntry) IfdPath() string

IfdPath returns the fully-qualified path of the IFD that owns this tag.

func (*IfdTagEntry) IsThumbnailOffset Uses

func (ite *IfdTagEntry) IsThumbnailOffset() bool

IsThumbnailOffset returns true if the tag has the IFD and tag-ID of a thumbnail offset.

func (*IfdTagEntry) IsThumbnailSize Uses

func (ite *IfdTagEntry) IsThumbnailSize() bool

IsThumbnailSize returns true if the tag has the IFD and tag-ID of a thumbnail size.

func (*IfdTagEntry) SetChildIfd Uses

func (ite *IfdTagEntry) SetChildIfd(ii *exifcommon.IfdIdentity)

SetChildIfd sets child-IFD information (if we represent a child IFD).

func (*IfdTagEntry) String Uses

func (ite *IfdTagEntry) String() string

String returns a stringified representation of the struct.

func (*IfdTagEntry) TagId Uses

func (ite *IfdTagEntry) TagId() uint16

TagId returns the ID of the tag that we represent. The combination of (IfdPath(), TagId()) is unique.

func (*IfdTagEntry) TagName Uses

func (ite *IfdTagEntry) TagName() string

TagName returns the name of the tag. This is determined else and set after the parse (since it's not actually stored in the stream). If it's empty, it is because it is an unknown tag (nonstandard or otherwise unavailable in the tag-index).

func (*IfdTagEntry) TagType Uses

func (ite *IfdTagEntry) TagType() exifcommon.TagTypePrimitive

TagType is the type of value for this tag.

func (*IfdTagEntry) UnitCount Uses

func (ite *IfdTagEntry) UnitCount() uint32

UnitCount returns the unit-count of the tag's value.

func (*IfdTagEntry) Value Uses

func (ite *IfdTagEntry) Value() (value interface{}, err error)

Value returns the specific, parsed, typed value from the tag.

type IndexedTag Uses

type IndexedTag struct {
    // Id is the tag-ID.
    Id  uint16

    // Name is the tag name.
    Name string

    // IfdPath is the proper IFD path of this tag. This is not fully-qualified.
    IfdPath string

    // SupportedTypes is an unsorted list of allowed tag-types.
    SupportedTypes []exifcommon.TagTypePrimitive
}

IndexedTag describes one index lookup result.

func (*IndexedTag) DoesSupportType Uses

func (it *IndexedTag) DoesSupportType(tagType exifcommon.TagTypePrimitive) bool

DoesSupportType returns true if this tag can be found/decoded with this type.

func (*IndexedTag) GetEncodingType Uses

func (it *IndexedTag) GetEncodingType(value interface{}) exifcommon.TagTypePrimitive

GetEncodingType returns the largest type that this tag's value can occupy.

func (*IndexedTag) Is Uses

func (it *IndexedTag) Is(ifdPath string, id uint16) bool

Is returns true if this tag matched the given tag ID.

func (*IndexedTag) IsName Uses

func (it *IndexedTag) IsName(ifdPath, name string) bool

IsName returns true if this tag matches the given tag name.

func (*IndexedTag) String Uses

func (it *IndexedTag) String() string

String returns a descriptive string.

type MiscellaneousExifData Uses

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

MiscellaneousExifData is reports additional data collected during the parse.

func (*MiscellaneousExifData) UnknownTags Uses

func (med *MiscellaneousExifData) UnknownTags() map[exifcommon.BasicTag]exifcommon.BasicTag

UnknownTags returns the unknown tags encountered during the scan.

type ParsedTagVisitor Uses

type ParsedTagVisitor func(*Ifd, *IfdTagEntry) error

ParsedTagVisitor is a callback used if wanting to visit through all tags and child IFDs from the current IFD and going down.

type QueuedIfd Uses

type QueuedIfd struct {
    IfdIdentity *exifcommon.IfdIdentity

    Offset uint32
    Parent *Ifd

    // ParentTagIndex is our tag position in the parent IFD, if we had a parent
    // (if `ParentIfd` is not nil and we weren't an IFD referenced as a sibling
    // instead of as a child).
    ParentTagIndex int
}

QueuedIfd is one IFD that has been identified but yet to be processed.

type ScanOptions Uses

type ScanOptions struct {
}

ScanOptions tweaks parser behavior/choices.

type TagIndex Uses

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

TagIndex is a tag-lookup facility.

func NewTagIndex Uses

func NewTagIndex() *TagIndex

NewTagIndex returns a new TagIndex struct.

func (*TagIndex) Add Uses

func (ti *TagIndex) Add(it *IndexedTag) (err error)

Add registers a new tag to be recognized during the parse.

func (*TagIndex) FindFirst Uses

func (ti *TagIndex) FindFirst(id uint16, typeId exifcommon.TagTypePrimitive, ifdIdentities []*exifcommon.IfdIdentity) (it *IndexedTag, err error)

FindFirst looks for the given tag-ID in each of the given IFDs in the given order. If `fqIfdPaths` is `nil` then use a default search order. This defies the standard, which requires each tag to exist in certain IFDs. This is a contingency to make recommendations for malformed data.

Things *can* end badly here, in that the same tag-ID in different IFDs might describe different data and different ata-types, and our decode might then produce binary and non-printable data.

func (*TagIndex) Get Uses

func (ti *TagIndex) Get(ii *exifcommon.IfdIdentity, id uint16) (it *IndexedTag, err error)

Get returns information about the non-IFD tag given a tag ID. `ifdPath` must not be fully-qualified.

func (*TagIndex) GetWithName Uses

func (ti *TagIndex) GetWithName(ii *exifcommon.IfdIdentity, name string) (it *IndexedTag, err error)

GetWithName returns information about the non-IFD tag given a tag name.

type TagVisitorFn Uses

type TagVisitorFn func(ite *IfdTagEntry) (err error)

TagVisitorFn is called for each tag when enumerating through the EXIF.

Directories

PathSynopsis
common
undefined

Package exif imports 21 packages (graph) and is imported by 5 packages. Updated 2020-08-26. Refresh now. Tools for package owners.