func ParseIFD(br tiff.BReader, offset uint64, tsp tiff.TagSpace, ftsp tiff.FieldTypeSpace) (out tiff.IFD, err error) {
if br == nil {
return nil, errors.New("tiff: no BReader supplied")
}
if ftsp == nil {
ftsp = tiff.DefaultFieldTypeSpace
}
if tsp == nil {
tsp = tiff.DefaultTagSpace
}
ifd := &imageFileDirectory{
fieldMap: make(map[uint16]tiff.Field, 1),
}
br.Seek(int64(offset), 0)
if err = br.BRead(&ifd.numEntries); err != nil {
err = fmt.Errorf("bigtiff: unable to read the number of entries for the IFD at offset %#08x: %v", offset, err)
return
}
for i := uint64(0); i < ifd.numEntries; i++ {
var f tiff.Field
if f, err = ParseField(br, tsp, ftsp); err != nil {
return
}
ifd.fields = append(ifd.fields, f)
ifd.fieldMap[f.Tag().ID()] = f
}
if err = br.BRead(&ifd.nextOffset); err != nil {
err = fmt.Errorf("bigtiff: unable to read the offset for the next ifd: %v", err)
return
}
return ifd, nil
}
func fiExposureProgram(f tiff.Field) string {
prog := f.Type().Valuer()(f.Value().Bytes(), f.Value().Order()).Uint()
if prog >= uint64(len(exposureProgramVals)) {
return ""
}
return exposureProgramVals[prog]
}
// fiRatAsFloat displays a rational as a float with 2 decimal points.
func fiRatAsFloat(f tiff.Field) string {
return f.Type().Valuer()(f.Value().Bytes(), f.Value().Order()).Interface().(*big.Rat).FloatString(2)
}