mirror of https://github.com/dsoprea/go-exif.git
77 lines
1.7 KiB
Go
77 lines
1.7 KiB
Go
package exif
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import (
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"errors"
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"bytes"
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"encoding/binary"
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"github.com/dsoprea/go-logging"
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)
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var (
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exifLogger = log.NewLogger("exif.exif")
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ErrNotExif = errors.New("not exif data")
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)
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type Exif struct {
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}
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func NewExif() *Exif {
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return new(Exif)
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}
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func (e *Exif) IsExif(data []byte) (ok bool) {
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if bytes.Compare(data[:6], []byte("Exif\000\000")) == 0 {
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return true
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}
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return false
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}
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func (e *Exif) Parse(data []byte, visitor TagVisitor) (err error) {
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defer func() {
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if state := recover(); state != nil {
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err = log.Wrap(state.(error))
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}
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}()
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if e.IsExif(data) == false {
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log.Panic(ErrNotExif)
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}
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// Good reference:
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//
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// CIPA DC-008-2016; JEITA CP-3451D
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// -> http://www.cipa.jp/std/documents/e/DC-008-Translation-2016-E.pdf
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byteOrderSignature := data[6:8]
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byteOrder := IfdByteOrder(BigEndianByteOrder)
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if string(byteOrderSignature) == "II" {
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byteOrder = IfdByteOrder(LittleEndianByteOrder)
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} else if string(byteOrderSignature) != "MM" {
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log.Panicf("byte-order not recognized: [%v]", byteOrderSignature)
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}
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fixedBytes := data[8:10]
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if fixedBytes[0] != 0x2a || fixedBytes[1] != 0x00 {
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exifLogger.Warningf(nil, "EXIF app-data header fixed-bytes should be 0x002a but are: [%v]", fixedBytes)
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return nil
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}
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firstIfdOffset := uint32(0)
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if byteOrder.IsLittleEndian() == true {
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firstIfdOffset = binary.LittleEndian.Uint32(data[10:14])
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} else {
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firstIfdOffset = binary.BigEndian.Uint32(data[10:14])
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}
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ifd := NewIfd(data, byteOrder)
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err = ifd.Scan(IfdStandard, firstIfdOffset, visitor)
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log.PanicIf(err)
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return nil
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}
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