goexiv

package module
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 Go to latest Published: Mar 2, 2023 License: MIT Imports: 4 Imported by: 5

README

Build Status

Go bindings for exiv2 (http://www.exiv2.org)

The library allows reading and writing EXIF and IPTC metadata to/from JPG, WEBP, and PNG images.

It is based on https://github.com/abustany/goexiv and https://github.com/gitschneider/goexiv with support added for writing the metadata and various bugfixes.

Библиотека для записи и чтения метаданных EXIF и IPTC в изображениях формата JPG, WEBP и PNG. Основана на https://github.com/abustany/goexiv и https://github.com/gitschneider/goexiv с добавленной фукнциональностью для записи метаданных и исправлением ошибок.

Requirements

A libexiv2 library v0.27 is required (this might also work with newer versions, but it hasn't been tested).

On Ubuntu, libexiv2 can be installed from the package manager (sudo apt install libexiv2-dev), but there is no guarantee it comes with the version needed. So it is safer to install it manually:

  • Download and unpack the library from https://github.com/Exiv2/exiv2/releases/tag/v0.27.2
  • Install the library (the steps are taken from libexiv2 README): 
    mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release
cmake --build .
sudo make install
sudo ldconfig
  • It may be needed to set the following variable: export PKG_CONFIG_PATH=/usr/local/lib64/pkgconfig

Now the Go code in this project can interface with the libexiv2 library.

The installation process for other operating systems should be similar. Also, this library is tested with golang:1.13-alpine docker image, where the correct version of libexiv2 is installed with apk --update add exiv2-dev.

Usage

Basic usage:

import "github.com/kolesa-team/goexiv"

// Open an image from disk
goexivImg, err := goexiv.Open("/path/to/image.jpg")
if err != nil {
    return err
}

// Write an EXIF comment
err = goexivImg.SetMetadataString("exif", "Exif.Photo.UserComment", "A comment. Might be a JSON string. Можно писать и по-русски!")
if err != nil {
    return err
}

// Write an EXIF short integer
err = goexivImg.SetMetadataShort("exif", "Exif.Photo.ExposureProgram", "2")
if err != nil {
    return err
}

// Read metadata
err = goexivImg.ReadMetadata()
if err != nil {
    return err
}

// Read an EXIF comment
userComment, err := goexivImg.GetExifData().GetString("Exif.Photo.UserComment")
if err != nil {
    return err
}

fmt.Println(userComment)
// "A comment. Might be a JSON string. Можно писать и по-русски!"

// It is advisable to insert this line at the end of `goexivImg` lifecycle.  
// see exiv_test.go:Test_GetBytes_Goroutine
runtime.KeepAlive(goexivImg)

Changing the image metadata in memory and returning the updated image (an approach fit for a web service):

// Say we have an image in memory: var img []byte
goexivImg, err := goexiv.OpenBytes(img)
if err != nil {
    return err
}

// Write an IPTC comment
err = goexivImg.SetMetadataString("iptc", "Iptc.Application2.Caption", "A comment. Might be a JSON string.")
if err != nil {
    return err
}

// Get back the modified image, so it can now be further processed (e.g. sent over the network)
img = goexivImg.GetBytes()

Retrieving all metadata keys and values:

img.ReadMetadata()
// map[string]string
exif := img.GetExifData().AllTags()

// map[string]string
iptc := img.GetIptcData().AllTags()

A complete image processing workflow in Go can be organized with the following additional libraries:

Documentation

Index

Constants

View Source 
const (
	LogMsgDebug LogMsgLevel = 0
	LogMsgInfo              = 1
	LogMsgWarn              = 2
	LogMsgError             = 3
	LogMsgMute              = 4
)

Variables

View Source 
var ErrMetadataKeyNotFound = errors.New("key not found")

Functions

func SetLogMsgLevel added in v1.1.0 

func SetLogMsgLevel(level LogMsgLevel)

SetLogMsgLevel Set the log level (outputs to stderr)

Types

type Error 

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

func (*Error) Code 

func (e *Error) Code() int

func (*Error) Error 

func (e *Error) Error() string

type ExifData 

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

func (*ExifData) AllTags 

func (d *ExifData) AllTags() map[string]string

Returns all EXIF tags

func (*ExifData) FindKey 

func (d *ExifData) FindKey(key string) (*ExifDatum, error)

func (*ExifData) GetString 

func (d *ExifData) GetString(key string) (string, error)

func (*ExifData) Iterator 

func (d *ExifData) Iterator() *ExifDatumIterator

Iterator returns a new ExifDatumIterator to iterate over all Exif data.

type ExifDatum 

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

func (*ExifDatum) Key 

func (d *ExifDatum) Key() string

Key returns the Exif key of the datum.

func (*ExifDatum) String 

func (d *ExifDatum) String() string

type ExifDatumIterator 

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

ExifDatumIterator wraps the respective C++ structure.

func (*ExifDatumIterator) HasNext 

func (i *ExifDatumIterator) HasNext() bool

HasNext returns true as long as the iterator has another datum to deliver.

func (*ExifDatumIterator) Next 

func (i *ExifDatumIterator) Next() *ExifDatum

Next returns the next ExifDatum of the iterator or nil if iterator has reached the end.

type Image 

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

func Open 

func Open(path string) (*Image, error)

Open opens an image file from the filesystem and returns a pointer to the corresponding Image object, but does not read the Metadata. Start the parsing with a call to ReadMetadata()

func OpenBytes 

func OpenBytes(input []byte) (*Image, error)

OpenBytes opens a byte slice with image data and returns a pointer to the corresponding Image object, but does not read the Metadata. Start the parsing with a call to ReadMetadata()

func (*Image) ExifStripKey added in v1.2.0 

func (i *Image) ExifStripKey(key string) error

func (*Image) GetBytes 

func (i *Image) GetBytes() []byte

Returns an image contents. If its metadata has been changed, the changes are reflected here.

func (*Image) GetExifData 

func (i *Image) GetExifData() *ExifData

func (*Image) GetIptcData 

func (i *Image) GetIptcData() *IptcData

func (*Image) GetXmpData 

func (i *Image) GetXmpData() *XmpData

GetXmpData returns the XmpData of an Image.

func (*Image) ICCProfile 

func (i *Image) ICCProfile() []byte

ICCProfile returns the ICC profile or nil if the image doesn't has one.

func (*Image) IptcStripKey added in v1.2.0 

func (i *Image) IptcStripKey(key string) error

func (*Image) PixelHeight 

func (i *Image) PixelHeight() int64

PixelHeight returns the height of the image in pixels

func (*Image) PixelWidth 

func (i *Image) PixelWidth() int64

PixelWidth returns the width of the image in pixels

func (*Image) ReadMetadata 

func (i *Image) ReadMetadata() error

ReadMetadata reads the metadata of an Image

func (*Image) SetExifString 

func (i *Image) SetExifString(key, value string) error

func (*Image) SetIptcShort added in v1.0.1 

func (i *Image) SetIptcShort(key, value string) error

func (*Image) SetIptcString 

func (i *Image) SetIptcString(key, value string) error

func (*Image) SetMetadataShort added in v1.0.1 

func (i *Image) SetMetadataShort(format, key, value string) error

Sets an exif or iptc key with a given short value

func (*Image) SetMetadataString 

func (i *Image) SetMetadataString(format, key, value string) error

Sets an exif or iptc key with a given string value

func (*Image) StripKey added in v1.2.0 

func (i *Image) StripKey(f MetadataFormat, key string) error

func (*Image) XmpStripKey added in v1.2.0 

func (i *Image) XmpStripKey(key string) error

type IptcData 

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

func (*IptcData) AllTags 

func (d *IptcData) AllTags() map[string]string

Returns all IPTC tags

func (*IptcData) FindKey 

func (d *IptcData) FindKey(key string) (*IptcDatum, error)

func (*IptcData) GetString 

func (d *IptcData) GetString(key string) (string, error)

func (*IptcData) Iterator 

func (d *IptcData) Iterator() *IptcDatumIterator

Iterator returns a new IptcDatumIterator to iterate over all IPTC data.

type IptcDatum 

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

func (*IptcDatum) Key 

func (d *IptcDatum) Key() string

Key returns the IPTC key of the datum.

func (*IptcDatum) String 

func (d *IptcDatum) String() string

type IptcDatumIterator 

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

IptcDatumIterator wraps the respective C++ structure.

func (*IptcDatumIterator) HasNext 

func (i *IptcDatumIterator) HasNext() bool

HasNext returns true as long as the iterator has another datum to deliver.

func (*IptcDatumIterator) Next 

func (i *IptcDatumIterator) Next() *IptcDatum

Next returns the next IptcDatum of the iterator or nil if iterator has reached the end.

type LogMsgLevel added in v1.1.0 

type LogMsgLevel int

type MetadataFormat added in v1.2.0 

type MetadataFormat int
const (
	EXIF MetadataFormat = iota
	IPTC
	XMP
)

type MetadataProvider 

type MetadataProvider interface {
	GetString(key string) (string, error)
}

type XmpData 

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

XmpData contains all Xmp Data of an image.

func (*XmpData) FindKey 

func (d *XmpData) FindKey(key string) (*XmpDatum, error)

FindKey tries to find the specified key and returns its data. It returns an error if the key is invalid. If the key is not found, a nil pointer will be returned

type XmpDatum 

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

XmpDatum stores the info of one xmp datum.

func (*XmpDatum) String 

func (d *XmpDatum) String() string

Source Files

View all Source files

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