Exemplo n.º 1
0
func Parse(r io.Reader) (eIFD, gIFD, ioIFD tiff.IFD, err error) {
	rars := tiff.NewReadAtReadSeeker(r)
	var two [2]byte
	if _, err = rars.Read(two[:]); err != nil {
		return
	}

	if _, err = rars.Seek(0, 0); err != nil {
		return
	}

	switch string(two[:]) {
	case "MM", "II": // likely a tiff
		var t tiff.TIFF
		if t, err = tiff.Parse(rars, nil, nil); err != nil {
			return
		}
		for _, tIFD := range t.IFDs() {
			if tIFD.HasField(ExifIFDTagID) {
				eFld := tIFD.GetField(ExifIFDTagID)
				offset := eFld.Type().Valuer()(eFld.Value().Bytes(), eFld.Value().Order()).Uint()
				if eIFD, err = tiff.ParseIFD(t.R(), offset, ExifTagSpace, nil); err != nil {
					return
				}
				if tIFD.HasField(GPSIFDTagID) {
					gFld := tIFD.GetField(GPSIFDTagID)
					offset = gFld.Type().Valuer()(gFld.Value().Bytes(), gFld.Value().Order()).Uint()
					if gIFD, err = tiff.ParseIFD(t.R(), offset, GPSTagSpace, nil); err != nil {
						log.Printf("exif: GPS IFD found, but had trouble retrieving it from offset %d: %v\n", offset, err)
					}
				}
				if tIFD.HasField(InteroperabilityIFDTagID) {
					ioFld := tIFD.GetField(InteroperabilityIFDTagID)
					offset = ioFld.Type().Valuer()(ioFld.Value().Bytes(), ioFld.Value().Order()).Uint()
					if ioIFD, err = tiff.ParseIFD(t.R(), offset, IOPTagSpace, nil); err != nil {
						log.Printf("exif: IOP IFD found, but had trouble retrieving it from offset %d: %v\n", offset, err)
					}
				}
				return
			}
		}
		err = fmt.Errorf("exif: no exif ifd found in tiff")
		return
	case "\xff\xd8": // likely a jpeg
		err = fmt.Errorf("exif: still working on jpeg support")
		return
	}
	// Anything else is currently unsupported.
	err = fmt.Errorf("exif: unsupported header: %q", two[:])
	return
}
Exemplo n.º 2
-23
func getDecoder(t tiff.TIFF) (dec Decoder, err error) {
	if err = validateTIFF(t); err != nil {
		return
	}

	// Look for alternates that can handle the whole tiff.
	if handlr := findAlternateTIFFHandler(t); handlr != nil {
		return handlr.Decoder(t)
	}

	// Look for alternates that can handle specific IFDs.
	for _, ifd := range t.IFDs() {
		if handlr := findAlternateIFDHandler(ifd); handlr != nil {
			return handlr.Decoder(ifd, t.R())
		}
	}

	// If no alternates are found...  do our own thing as best we can, which
	// means baseline support only.
	ifd0 := t.IFDs()[0]
	if !new(BaselineHandler).CanHandle(ifd0) {
		return nil, fmt.Errorf("tiff/image: no handlers available for this tiff")
	}
	return new(BaselineHandler).Decoder(ifd0, t.R())
}