PLT-173 Added graphics-go and goexif libraries for image manipulation

Godeps/_workspace/src/github.com/rwcarlsen/goexif/exif/README.md

@@ -0,0 +1,4 @@
+
+To regenerate the regression test data, run `go generate` inside the exif
+package directory and commit the changes to *regress_expected_test.go*.
+

Godeps/_workspace/src/github.com/rwcarlsen/goexif/exif/example_test.go

@@ -0,0 +1,42 @@
+package exif_test
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/rwcarlsen/goexif/exif"
+	"github.com/rwcarlsen/goexif/mknote"
+)
+
+func ExampleDecode() {
+	fname := "sample1.jpg"
+
+	f, err := os.Open(fname)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Optionally register camera makenote data parsing - currently Nikon and
+	// Canon are supported.
+	exif.RegisterParsers(mknote.All...)
+
+	x, err := exif.Decode(f)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	camModel, _ := x.Get(exif.Model) // normally, don't ignore errors!
+	fmt.Println(camModel.StringVal())
+
+	focal, _ := x.Get(exif.FocalLength)
+	numer, denom, _ := focal.Rat2(0) // retrieve first (only) rat. value
+	fmt.Printf("%v/%v", numer, denom)
+
+	// Two convenience functions exist for date/time taken and GPS coords:
+	tm, _ := x.DateTime()
+	fmt.Println("Taken: ", tm)
+
+	lat, long, _ := x.LatLong()
+	fmt.Println("lat, long: ", lat, ", ", long)
+}

Godeps/_workspace/src/github.com/rwcarlsen/goexif/exif/exif.go

@@ -0,0 +1,619 @@
+// Package exif implements decoding of EXIF data as defined in the EXIF 2.2
+// specification (http://www.exif.org/Exif2-2.PDF).
+package exif
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/binary"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"math"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/rwcarlsen/goexif/tiff"
+)
+
+const (
+	jpeg_APP1 = 0xE1
+
+	exifPointer    = 0x8769
+	gpsPointer     = 0x8825
+	interopPointer = 0xA005
+)
+
+// A decodeError is returned when the image cannot be decoded as a tiff image.
+type decodeError struct {
+	cause error
+}
+
+func (de decodeError) Error() string {
+	return fmt.Sprintf("exif: decode failed (%v) ", de.cause.Error())
+}
+
+// IsShortReadTagValueError identifies a ErrShortReadTagValue error.
+func IsShortReadTagValueError(err error) bool {
+	de, ok := err.(decodeError)
+	if ok {
+		return de.cause == tiff.ErrShortReadTagValue
+	}
+	return false
+}
+
+// A TagNotPresentError is returned when the requested field is not
+// present in the EXIF.
+type TagNotPresentError FieldName
+
+func (tag TagNotPresentError) Error() string {
+	return fmt.Sprintf("exif: tag %q is not present", string(tag))
+}
+
+func IsTagNotPresentError(err error) bool {
+	_, ok := err.(TagNotPresentError)
+	return ok
+}
+
+// Parser allows the registration of custom parsing and field loading
+// in the Decode function.
+type Parser interface {
+	// Parse should read data from x and insert parsed fields into x via
+	// LoadTags.
+	Parse(x *Exif) error
+}
+
+var parsers []Parser
+
+func init() {
+	RegisterParsers(&parser{})
+}
+
+// RegisterParsers registers one or more parsers to be automatically called
+// when decoding EXIF data via the Decode function.
+func RegisterParsers(ps ...Parser) {
+	parsers = append(parsers, ps...)
+}
+
+type parser struct{}
+
+type tiffErrors map[tiffError]string
+
+func (te tiffErrors) Error() string {
+	var allErrors []string
+	for k, v := range te {
+		allErrors = append(allErrors, fmt.Sprintf("%s: %v\n", stagePrefix[k], v))
+	}
+	return strings.Join(allErrors, "\n")
+}
+
+// IsCriticalError, given the error returned by Decode, reports whether the
+// returned *Exif may contain usable information.
+func IsCriticalError(err error) bool {
+	_, ok := err.(tiffErrors)
+	return !ok
+}
+
+// IsExifError reports whether the error happened while decoding the EXIF
+// sub-IFD.
+func IsExifError(err error) bool {
+	if te, ok := err.(tiffErrors); ok {
+		_, isExif := te[loadExif]
+		return isExif
+	}
+	return false
+}
+
+// IsGPSError reports whether the error happened while decoding the GPS sub-IFD.
+func IsGPSError(err error) bool {
+	if te, ok := err.(tiffErrors); ok {
+		_, isGPS := te[loadExif]
+		return isGPS
+	}
+	return false
+}
+
+// IsInteroperabilityError reports whether the error happened while decoding the
+// Interoperability sub-IFD.
+func IsInteroperabilityError(err error) bool {
+	if te, ok := err.(tiffErrors); ok {
+		_, isInterop := te[loadInteroperability]
+		return isInterop
+	}
+	return false
+}
+
+type tiffError int
+
+const (
+	loadExif tiffError = iota
+	loadGPS
+	loadInteroperability
+)
+
+var stagePrefix = map[tiffError]string{
+	loadExif:             "loading EXIF sub-IFD",
+	loadGPS:              "loading GPS sub-IFD",
+	loadInteroperability: "loading Interoperability sub-IFD",
+}
+
+// Parse reads data from the tiff data in x and populates the tags
+// in x. If parsing a sub-IFD fails, the error is recorded and
+// parsing continues with the remaining sub-IFDs.
+func (p *parser) Parse(x *Exif) error {
+	x.LoadTags(x.Tiff.Dirs[0], exifFields, false)
+
+	// thumbnails
+	if len(x.Tiff.Dirs) >= 2 {
+		x.LoadTags(x.Tiff.Dirs[1], thumbnailFields, false)
+	}
+
+	te := make(tiffErrors)
+
+	// recurse into exif, gps, and interop sub-IFDs
+	if err := loadSubDir(x, ExifIFDPointer, exifFields); err != nil {
+		te[loadExif] = err.Error()
+	}
+	if err := loadSubDir(x, GPSInfoIFDPointer, gpsFields); err != nil {
+		te[loadGPS] = err.Error()
+	}
+
+	if err := loadSubDir(x, InteroperabilityIFDPointer, interopFields); err != nil {
+		te[loadInteroperability] = err.Error()
+	}
+	if len(te) > 0 {
+		return te
+	}
+	return nil
+}
+
+func loadSubDir(x *Exif, ptr FieldName, fieldMap map[uint16]FieldName) error {
+	r := bytes.NewReader(x.Raw)
+
+	tag, err := x.Get(ptr)
+	if err != nil {
+		return nil
+	}
+	offset, err := tag.Int64(0)
+	if err != nil {
+		return nil
+	}
+
+	_, err = r.Seek(offset, 0)
+	if err != nil {
+		return fmt.Errorf("exif: seek to sub-IFD %s failed: %v", ptr, err)
+	}
+	subDir, _, err := tiff.DecodeDir(r, x.Tiff.Order)
+	if err != nil {
+		return fmt.Errorf("exif: sub-IFD %s decode failed: %v", ptr, err)
+	}
+	x.LoadTags(subDir, fieldMap, false)
+	return nil
+}
+
+// Exif provides access to decoded EXIF metadata fields and values.
+type Exif struct {
+	Tiff *tiff.Tiff
+	main map[FieldName]*tiff.Tag
+	Raw  []byte
+}
+
+// Decode parses EXIF-encoded data from r and returns a queryable Exif
+// object. After the exif data section is called and the tiff structure
+// decoded, each registered parser is called (in order of registration). If
+// one parser returns an error, decoding terminates and the remaining
+// parsers are not called.
+// The error can be inspected with functions such as IsCriticalError to
+// determine whether the returned object might still be usable.
+func Decode(r io.Reader) (*Exif, error) {
+	// EXIF data in JPEG is stored in the APP1 marker. EXIF data uses the TIFF
+	// format to store data.
+	// If we're parsing a TIFF image, we don't need to strip away any data.
+	// If we're parsing a JPEG image, we need to strip away the JPEG APP1
+	// marker and also the EXIF header.
+
+	header := make([]byte, 4)
+	n, err := r.Read(header)
+	if err != nil {
+		return nil, err
+	}
+	if n < len(header) {
+		return nil, errors.New("exif: short read on header")
+	}
+
+	var isTiff bool
+	switch string(header) {
+	case "II*\x00":
+		// TIFF - Little endian (Intel)
+		isTiff = true
+	case "MM\x00*":
+		// TIFF - Big endian (Motorola)
+		isTiff = true
+	default:
+		// Not TIFF, assume JPEG
+	}
+
+	// Put the header bytes back into the reader.
+	r = io.MultiReader(bytes.NewReader(header), r)
+	var (
+		er  *bytes.Reader
+		tif *tiff.Tiff
+	)
+
+	if isTiff {
+		// Functions below need the IFDs from the TIFF data to be stored in a
+		// *bytes.Reader.  We use TeeReader to get a copy of the bytes as a
+		// side-effect of tiff.Decode() doing its work.
+		b := &bytes.Buffer{}
+		tr := io.TeeReader(r, b)
+		tif, err = tiff.Decode(tr)
+		er = bytes.NewReader(b.Bytes())
+	} else {
+		// Locate the JPEG APP1 header.
+		var sec *appSec
+		sec, err = newAppSec(jpeg_APP1, r)
+		if err != nil {
+			return nil, err
+		}
+		// Strip away EXIF header.
+		er, err = sec.exifReader()
+		if err != nil {
+			return nil, err
+		}
+		tif, err = tiff.Decode(er)
+	}
+
+	if err != nil {
+		return nil, decodeError{cause: err}
+	}
+
+	er.Seek(0, 0)
+	raw, err := ioutil.ReadAll(er)
+	if err != nil {
+		return nil, decodeError{cause: err}
+	}
+
+	// build an exif structure from the tiff
+	x := &Exif{
+		main: map[FieldName]*tiff.Tag{},
+		Tiff: tif,
+		Raw:  raw,
+	}
+
+	for i, p := range parsers {
+		if err := p.Parse(x); err != nil {
+			if _, ok := err.(tiffErrors); ok {
+				return x, err
+			}
+			// This should never happen, as Parse always returns a tiffError
+			// for now, but that could change.
+			return x, fmt.Errorf("exif: parser %v failed (%v)", i, err)
+		}
+	}
+
+	return x, nil
+}
+
+// LoadTags loads tags into the available fields from the tiff Directory
+// using the given tagid-fieldname mapping.  Used to load makernote and
+// other meta-data.  If showMissing is true, tags in d that are not in the
+// fieldMap will be loaded with the FieldName UnknownPrefix followed by the
+// tag ID (in hex format).
+func (x *Exif) LoadTags(d *tiff.Dir, fieldMap map[uint16]FieldName, showMissing bool) {
+	for _, tag := range d.Tags {
+		name := fieldMap[tag.Id]
+		if name == "" {
+			if !showMissing {
+				continue
+			}
+			name = FieldName(fmt.Sprintf("%v%x", UnknownPrefix, tag.Id))
+		}
+		x.main[name] = tag
+	}
+}
+
+// Get retrieves the EXIF tag for the given field name.
+//
+// If the tag is not known or not present, an error is returned. If the
+// tag name is known, the error will be a TagNotPresentError.
+func (x *Exif) Get(name FieldName) (*tiff.Tag, error) {
+	if tg, ok := x.main[name]; ok {
+		return tg, nil
+	}
+	return nil, TagNotPresentError(name)
+}
+
+// Walker is the interface used to traverse all fields of an Exif object.
+type Walker interface {
+	// Walk is called for each non-nil EXIF field. Returning a non-nil
+	// error aborts the walk/traversal.
+	Walk(name FieldName, tag *tiff.Tag) error
+}
+
+// Walk calls the Walk method of w with the name and tag for every non-nil
+// EXIF field.  If w aborts the walk with an error, that error is returned.
+func (x *Exif) Walk(w Walker) error {
+	for name, tag := range x.main {
+		if err := w.Walk(name, tag); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// DateTime returns the EXIF's "DateTimeOriginal" field, which
+// is the creation time of the photo. If not found, it tries
+// the "DateTime" (which is meant as the modtime) instead.
+// The error will be TagNotPresentErr if none of those tags
+// were found, or a generic error if the tag value was
+// not a string, or the error returned by time.Parse.
+//
+// If the EXIF lacks timezone information or GPS time, the returned
+// time's Location will be time.Local.
+func (x *Exif) DateTime() (time.Time, error) {
+	var dt time.Time
+	tag, err := x.Get(DateTimeOriginal)
+	if err != nil {
+		tag, err = x.Get(DateTime)
+		if err != nil {
+			return dt, err
+		}
+	}
+	if tag.Format() != tiff.StringVal {
+		return dt, errors.New("DateTime[Original] not in string format")
+	}
+	exifTimeLayout := "2006:01:02 15:04:05"
+	dateStr := strings.TrimRight(string(tag.Val), "\x00")
+	// TODO(bradfitz,mpl): look for timezone offset, GPS time, etc.
+	// For now, just always return the time.Local timezone.
+	return time.ParseInLocation(exifTimeLayout, dateStr, time.Local)
+}
+
+func ratFloat(num, dem int64) float64 {
+	return float64(num) / float64(dem)
+}
+
+// Tries to parse a Geo degrees value from a string as it was found in some
+// EXIF data.
+// Supported formats so far:
+// - "52,00000,50,00000,34,01180" ==> 52 deg 50'34.0118"
+//   Probably due to locale the comma is used as decimal mark as well as the
+//   separator of three floats (degrees, minutes, seconds)
+//   http://en.wikipedia.org/wiki/Decimal_mark#Hindu.E2.80.93Arabic_numeral_system
+// - "52.0,50.0,34.01180" ==> 52deg50'34.0118"
+// - "52,50,34.01180"     ==> 52deg50'34.0118"
+func parseTagDegreesString(s string) (float64, error) {
+	const unparsableErrorFmt = "Unknown coordinate format: %s"
+	isSplitRune := func(c rune) bool {
+		return c == ',' || c == ';'
+	}
+	parts := strings.FieldsFunc(s, isSplitRune)
+	var degrees, minutes, seconds float64
+	var err error
+	switch len(parts) {
+	case 6:
+		degrees, err = strconv.ParseFloat(parts[0]+"."+parts[1], 64)
+		if err != nil {
+			return 0.0, fmt.Errorf(unparsableErrorFmt, s)
+		}
+		minutes, err = strconv.ParseFloat(parts[2]+"."+parts[3], 64)
+		if err != nil {
+			return 0.0, fmt.Errorf(unparsableErrorFmt, s)
+		}
+		minutes = math.Copysign(minutes, degrees)
+		seconds, err = strconv.ParseFloat(parts[4]+"."+parts[5], 64)
+		if err != nil {
+			return 0.0, fmt.Errorf(unparsableErrorFmt, s)
+		}
+		seconds = math.Copysign(seconds, degrees)
+	case 3:
+		degrees, err = strconv.ParseFloat(parts[0], 64)
+		if err != nil {
+			return 0.0, fmt.Errorf(unparsableErrorFmt, s)
+		}
+		minutes, err = strconv.ParseFloat(parts[1], 64)
+		if err != nil {
+			return 0.0, fmt.Errorf(unparsableErrorFmt, s)
+		}
+		minutes = math.Copysign(minutes, degrees)
+		seconds, err = strconv.ParseFloat(parts[2], 64)
+		if err != nil {
+			return 0.0, fmt.Errorf(unparsableErrorFmt, s)
+		}
+		seconds = math.Copysign(seconds, degrees)
+	default:
+		return 0.0, fmt.Errorf(unparsableErrorFmt, s)
+	}
+	return degrees + minutes/60.0 + seconds/3600.0, nil
+}
+
+func parse3Rat2(tag *tiff.Tag) ([3]float64, error) {
+	v := [3]float64{}
+	for i := range v {
+		num, den, err := tag.Rat2(i)
+		if err != nil {
+			return v, err
+		}
+		v[i] = ratFloat(num, den)
+		if tag.Count < uint32(i+2) {
+			break
+		}
+	}
+	return v, nil
+}
+
+func tagDegrees(tag *tiff.Tag) (float64, error) {
+	switch tag.Format() {
+	case tiff.RatVal:
+		// The usual case, according to the Exif spec
+		// (http://www.kodak.com/global/plugins/acrobat/en/service/digCam/exifStandard2.pdf,
+		// sec 4.6.6, p. 52 et seq.)
+		v, err := parse3Rat2(tag)
+		if err != nil {
+			return 0.0, err
+		}
+		return v[0] + v[1]/60 + v[2]/3600.0, nil
+	case tiff.StringVal:
+		// Encountered this weird case with a panorama picture taken with a HTC phone
+		s, err := tag.StringVal()
+		if err != nil {
+			return 0.0, err
+		}
+		return parseTagDegreesString(s)
+	default:
+		// don't know how to parse value, give up
+		return 0.0, fmt.Errorf("Malformed EXIF Tag Degrees")
+	}
+}
+
+// LatLong returns the latitude and longitude of the photo and
+// whether it was present.
+func (x *Exif) LatLong() (lat, long float64, err error) {
+	// All calls of x.Get might return an TagNotPresentError
+	longTag, err := x.Get(FieldName("GPSLongitude"))
+	if err != nil {
+		return
+	}
+	ewTag, err := x.Get(FieldName("GPSLongitudeRef"))
+	if err != nil {
+		return
+	}
+	latTag, err := x.Get(FieldName("GPSLatitude"))
+	if err != nil {
+		return
+	}
+	nsTag, err := x.Get(FieldName("GPSLatitudeRef"))
+	if err != nil {
+		return
+	}
+	if long, err = tagDegrees(longTag); err != nil {
+		return 0, 0, fmt.Errorf("Cannot parse longitude: %v", err)
+	}
+	if lat, err = tagDegrees(latTag); err != nil {
+		return 0, 0, fmt.Errorf("Cannot parse latitude: %v", err)
+	}
+	ew, err := ewTag.StringVal()
+	if err == nil && ew == "W" {
+		long *= -1.0
+	} else if err != nil {
+		return 0, 0, fmt.Errorf("Cannot parse longitude: %v", err)
+	}
+	ns, err := nsTag.StringVal()
+	if err == nil && ns == "S" {
+		lat *= -1.0
+	} else if err != nil {
+		return 0, 0, fmt.Errorf("Cannot parse longitude: %v", err)
+	}
+	return lat, long, nil
+}
+
+// String returns a pretty text representation of the decoded exif data.
+func (x *Exif) String() string {
+	var buf bytes.Buffer
+	for name, tag := range x.main {
+		fmt.Fprintf(&buf, "%s: %s\n", name, tag)
+	}
+	return buf.String()
+}
+
+// JpegThumbnail returns the jpeg thumbnail if it exists. If it doesn't exist,
+// TagNotPresentError will be returned
+func (x *Exif) JpegThumbnail() ([]byte, error) {
+	offset, err := x.Get(ThumbJPEGInterchangeFormat)
+	if err != nil {
+		return nil, err
+	}
+	start, err := offset.Int(0)
+	if err != nil {
+		return nil, err
+	}
+
+	length, err := x.Get(ThumbJPEGInterchangeFormatLength)
+	if err != nil {
+		return nil, err
+	}
+	l, err := length.Int(0)
+	if err != nil {
+		return nil, err
+	}
+
+	return x.Raw[start : start+l], nil
+}
+
+// MarshalJson implements the encoding/json.Marshaler interface providing output of
+// all EXIF fields present (names and values).
+func (x Exif) MarshalJSON() ([]byte, error) {
+	return json.Marshal(x.main)
+}
+
+type appSec struct {
+	marker byte
+	data   []byte
+}
+
+// newAppSec finds marker in r and returns the corresponding application data
+// section.
+func newAppSec(marker byte, r io.Reader) (*appSec, error) {
+	br := bufio.NewReader(r)
+	app := &appSec{marker: marker}
+	var dataLen int
+
+	// seek to marker
+	for dataLen == 0 {
+		if _, err := br.ReadBytes(0xFF); err != nil {
+			return nil, err
+		}
+		c, err := br.ReadByte()
+		if err != nil {
+			return nil, err
+		} else if c != marker {
+			continue
+		}
+
+		dataLenBytes := make([]byte, 2)
+		for k,_ := range dataLenBytes {
+			c, err := br.ReadByte()
+			if err != nil {
+				return nil, err
+			}
+			dataLenBytes[k] = c
+		}
+		dataLen = int(binary.BigEndian.Uint16(dataLenBytes)) - 2
+	}
+
+	// read section data
+	nread := 0
+	for nread < dataLen {
+		s := make([]byte, dataLen-nread)
+		n, err := br.Read(s)
+		nread += n
+		if err != nil && nread < dataLen {
+			return nil, err
+		}
+		app.data = append(app.data, s[:n]...)
+	}
+	return app, nil
+}
+
+// reader returns a reader on this appSec.
+func (app *appSec) reader() *bytes.Reader {
+	return bytes.NewReader(app.data)
+}
+
+// exifReader returns a reader on this appSec with the read cursor advanced to
+// the start of the exif's tiff encoded portion.
+func (app *appSec) exifReader() (*bytes.Reader, error) {
+	if len(app.data) < 6 {
+		return nil, errors.New("exif: failed to find exif intro marker")
+	}
+
+	// read/check for exif special mark
+	exif := app.data[:6]
+	if !bytes.Equal(exif, append([]byte("Exif"), 0x00, 0x00)) {
+		return nil, errors.New("exif: failed to find exif intro marker")
+	}
+	return bytes.NewReader(app.data[6:]), nil
+}

Godeps/_workspace/src/github.com/rwcarlsen/goexif/exif/exif_test.go

@@ -0,0 +1,202 @@
+package exif
+
+//go:generate go run regen_regress.go -- regress_expected_test.go
+//go:generate go fmt regress_expected_test.go
+
+import (
+	"flag"
+	"fmt"
+	"math"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/rwcarlsen/goexif/tiff"
+)
+
+var dataDir = flag.String("test_data_dir", ".", "Directory where the data files for testing are located")
+
+func TestDecode(t *testing.T) {
+	fpath := filepath.Join(*dataDir, "samples")
+	f, err := os.Open(fpath)
+	if err != nil {
+		t.Fatalf("Could not open sample directory '%s': %v", fpath, err)
+	}
+
+	names, err := f.Readdirnames(0)
+	if err != nil {
+		t.Fatalf("Could not read sample directory '%s': %v", fpath, err)
+	}
+
+	cnt := 0
+	for _, name := range names {
+		if !strings.HasSuffix(name, ".jpg") {
+			t.Logf("skipping non .jpg file %v", name)
+			continue
+		}
+		t.Logf("testing file %v", name)
+		f, err := os.Open(filepath.Join(fpath, name))
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		x, err := Decode(f)
+		if err != nil {
+			t.Fatal(err)
+		} else if x == nil {
+			t.Fatalf("No error and yet %v was not decoded", name)
+		}
+
+		t.Logf("checking pic %v", name)
+		x.Walk(&walker{name, t})
+		cnt++
+	}
+	if cnt != len(regressExpected) {
+		t.Errorf("Did not process enough samples, got %d, want %d", cnt, len(regressExpected))
+	}
+}
+
+type walker struct {
+	picName string
+	t       *testing.T
+}
+
+func (w *walker) Walk(field FieldName, tag *tiff.Tag) error {
+	// this needs to be commented out when regenerating regress expected vals
+	pic := regressExpected[w.picName]
+	if pic == nil {
+		w.t.Errorf("   regression data not found")
+		return nil
+	}
+
+	exp, ok := pic[field]
+	if !ok {
+		w.t.Errorf("   regression data does not have field %v", field)
+		return nil
+	}
+
+	s := tag.String()
+	if tag.Count == 1 && s != "\"\"" {
+		s = fmt.Sprintf("[%s]", s)
+	}
+	got := tag.String()
+
+	if exp != got {
+		fmt.Println("s: ", s)
+		fmt.Printf("len(s)=%v\n", len(s))
+		w.t.Errorf("   field %v bad tag: expected '%s', got '%s'", field, exp, got)
+	}
+	return nil
+}
+
+func TestMarshal(t *testing.T) {
+	name := filepath.Join(*dataDir, "sample1.jpg")
+	f, err := os.Open(name)
+	if err != nil {
+		t.Fatalf("%v\n", err)
+	}
+	defer f.Close()
+
+	x, err := Decode(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if x == nil {
+		t.Fatal("bad err")
+	}
+
+	b, err := x.MarshalJSON()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Logf("%s", b)
+}
+
+func testSingleParseDegreesString(t *testing.T, s string, w float64) {
+	g, err := parseTagDegreesString(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if math.Abs(w-g) > 1e-10 {
+		t.Errorf("Wrong parsing result %s: Want %.12f, got %.12f", s, w, g)
+	}
+}
+
+func TestParseTagDegreesString(t *testing.T) {
+	// semicolon as decimal mark
+	testSingleParseDegreesString(t, "52,00000,50,00000,34,01180", 52.842781055556) // comma as separator
+	testSingleParseDegreesString(t, "52,00000;50,00000;34,01180", 52.842781055556) // semicolon as separator
+
+	// point as decimal mark
+	testSingleParseDegreesString(t, "14.00000,44.00000,34.01180", 14.742781055556) // comma as separator
+	testSingleParseDegreesString(t, "14.00000;44.00000;34.01180", 14.742781055556) // semicolon as separator
+	testSingleParseDegreesString(t, "14.00000;44.00000,34.01180", 14.742781055556) // mixed separators
+
+	testSingleParseDegreesString(t, "-008.0,30.0,03.6", -8.501) // leading zeros
+
+	// no decimal places
+	testSingleParseDegreesString(t, "-10,15,54", -10.265)
+	testSingleParseDegreesString(t, "-10;15;54", -10.265)
+
+	// incorrect mix of comma and point as decimal mark
+	s := "-17,00000,15.00000,04.80000"
+	if _, err := parseTagDegreesString(s); err == nil {
+		t.Error("parseTagDegreesString: false positive for " + s)
+	}
+}
+
+// Make sure we error out early when a tag had a count of MaxUint32
+func TestMaxUint32CountError(t *testing.T) {
+	name := filepath.Join(*dataDir, "corrupt/max_uint32_exif.jpg")
+	f, err := os.Open(name)
+	if err != nil {
+		t.Fatalf("%v\n", err)
+	}
+	defer f.Close()
+
+	_, err = Decode(f)
+	if err == nil {
+		t.Fatal("no error on bad exif data")
+	}
+	if !strings.Contains(err.Error(), "invalid Count offset") {
+		t.Fatal("wrong error:", err.Error())
+	}
+}
+
+// Make sure we error out early with tag data sizes larger than the image file
+func TestHugeTagError(t *testing.T) {
+	name := filepath.Join(*dataDir, "corrupt/huge_tag_exif.jpg")
+	f, err := os.Open(name)
+	if err != nil {
+		t.Fatalf("%v\n", err)
+	}
+	defer f.Close()
+
+	_, err = Decode(f)
+	if err == nil {
+		t.Fatal("no error on bad exif data")
+	}
+	if !strings.Contains(err.Error(), "short read") {
+		t.Fatal("wrong error:", err.Error())
+	}
+}
+
+// Check for a 0-length tag value
+func TestZeroLengthTagError(t *testing.T) {
+	name := filepath.Join(*dataDir, "corrupt/infinite_loop_exif.jpg")
+	f, err := os.Open(name)
+	if err != nil {
+		t.Fatalf("%v\n", err)
+	}
+	defer f.Close()
+
+	_, err = Decode(f)
+	if err == nil {
+		t.Fatal("no error on bad exif data")
+	}
+	if !strings.Contains(err.Error(), "zero length tag value") {
+		t.Fatal("wrong error:", err.Error())
+	}
+}

Godeps/_workspace/src/github.com/rwcarlsen/goexif/exif/fields.go

@@ -0,0 +1,293 @@
+package exif
+
+type FieldName string
+
+// UnknownPrefix is used as the first part of field names for decoded tags for
+// which there is no known/supported EXIF field.
+const UnknownPrefix = "UnknownTag_"
+
+// Primary EXIF fields
+const (
+	ImageWidth                 FieldName = "ImageWidth"
+	ImageLength                          = "ImageLength" // Image height called Length by EXIF spec
+	BitsPerSample                        = "BitsPerSample"
+	Compression                          = "Compression"
+	PhotometricInterpretation            = "PhotometricInterpretation"
+	Orientation                          = "Orientation"
+	SamplesPerPixel                      = "SamplesPerPixel"
+	PlanarConfiguration                  = "PlanarConfiguration"
+	YCbCrSubSampling                     = "YCbCrSubSampling"
+	YCbCrPositioning                     = "YCbCrPositioning"
+	XResolution                          = "XResolution"
+	YResolution                          = "YResolution"
+	ResolutionUnit                       = "ResolutionUnit"
+	DateTime                             = "DateTime"
+	ImageDescription                     = "ImageDescription"
+	Make                                 = "Make"
+	Model                                = "Model"
+	Software                             = "Software"
+	Artist                               = "Artist"
+	Copyright                            = "Copyright"
+	ExifIFDPointer                       = "ExifIFDPointer"
+	GPSInfoIFDPointer                    = "GPSInfoIFDPointer"
+	InteroperabilityIFDPointer           = "InteroperabilityIFDPointer"
+	ExifVersion                          = "ExifVersion"
+	FlashpixVersion                      = "FlashpixVersion"
+	ColorSpace                           = "ColorSpace"
+	ComponentsConfiguration              = "ComponentsConfiguration"
+	CompressedBitsPerPixel               = "CompressedBitsPerPixel"
+	PixelXDimension                      = "PixelXDimension"
+	PixelYDimension                      = "PixelYDimension"
+	MakerNote                            = "MakerNote"
+	UserComment                          = "UserComment"
+	RelatedSoundFile                     = "RelatedSoundFile"
+	DateTimeOriginal                     = "DateTimeOriginal"
+	DateTimeDigitized                    = "DateTimeDigitized"
+	SubSecTime                           = "SubSecTime"
+	SubSecTimeOriginal                   = "SubSecTimeOriginal"
+	SubSecTimeDigitized                  = "SubSecTimeDigitized"
+	ImageUniqueID                        = "ImageUniqueID"
+	ExposureTime                         = "ExposureTime"
+	FNumber                              = "FNumber"
+	ExposureProgram                      = "ExposureProgram"
+	SpectralSensitivity                  = "SpectralSensitivity"
+	ISOSpeedRatings                      = "ISOSpeedRatings"
+	OECF                                 = "OECF"
+	ShutterSpeedValue                    = "ShutterSpeedValue"
+	ApertureValue                        = "ApertureValue"
+	BrightnessValue                      = "BrightnessValue"
+	ExposureBiasValue                    = "ExposureBiasValue"
+	MaxApertureValue                     = "MaxApertureValue"
+	SubjectDistance                      = "SubjectDistance"
+	MeteringMode                         = "MeteringMode"
+	LightSource                          = "LightSource"
+	Flash                                = "Flash"
+	FocalLength                          = "FocalLength"
+	SubjectArea                          = "SubjectArea"
+	FlashEnergy                          = "FlashEnergy"
+	SpatialFrequencyResponse             = "SpatialFrequencyResponse"
+	FocalPlaneXResolution                = "FocalPlaneXResolution"
+	FocalPlaneYResolution                = "FocalPlaneYResolution"
+	FocalPlaneResolutionUnit             = "FocalPlaneResolutionUnit"
+	SubjectLocation                      = "SubjectLocation"
+	ExposureIndex                        = "ExposureIndex"
+	SensingMethod                        = "SensingMethod"
+	FileSource                           = "FileSource"
+	SceneType                            = "SceneType"
+	CFAPattern                           = "CFAPattern"
+	CustomRendered                       = "CustomRendered"
+	ExposureMode                         = "ExposureMode"
+	WhiteBalance                         = "WhiteBalance"
+	DigitalZoomRatio                     = "DigitalZoomRatio"
+	FocalLengthIn35mmFilm                = "FocalLengthIn35mmFilm"
+	SceneCaptureType                     = "SceneCaptureType"
+	GainControl                          = "GainControl"
+	Contrast                             = "Contrast"
+	Saturation                           = "Saturation"
+	Sharpness                            = "Sharpness"
+	DeviceSettingDescription             = "DeviceSettingDescription"
+	SubjectDistanceRange                 = "SubjectDistanceRange"
+	LensMake                             = "LensMake"
+	LensModel                            = "LensModel"
+)
+
+// thumbnail fields
+const (
+	ThumbJPEGInterchangeFormat       = "ThumbJPEGInterchangeFormat"       // offset to thumb jpeg SOI
+	ThumbJPEGInterchangeFormatLength = "ThumbJPEGInterchangeFormatLength" // byte length of thumb
+)
+
+// GPS fields
+const (
+	GPSVersionID        FieldName = "GPSVersionID"
+	GPSLatitudeRef                = "GPSLatitudeRef"
+	GPSLatitude                   = "GPSLatitude"
+	GPSLongitudeRef               = "GPSLongitudeRef"
+	GPSLongitude                  = "GPSLongitude"
+	GPSAltitudeRef                = "GPSAltitudeRef"
+	GPSAltitude                   = "GPSAltitude"
+	GPSTimeStamp                  = "GPSTimeStamp"
+	GPSSatelites                  = "GPSSatelites"
+	GPSStatus                     = "GPSStatus"
+	GPSMeasureMode                = "GPSMeasureMode"
+	GPSDOP                        = "GPSDOP"
+	GPSSpeedRef                   = "GPSSpeedRef"
+	GPSSpeed                      = "GPSSpeed"
+	GPSTrackRef                   = "GPSTrackRef"
+	GPSTrack                      = "GPSTrack"
+	GPSImgDirectionRef            = "GPSImgDirectionRef"
+	GPSImgDirection               = "GPSImgDirection"
+	GPSMapDatum                   = "GPSMapDatum"
+	GPSDestLatitudeRef            = "GPSDestLatitudeRef"
+	GPSDestLatitude               = "GPSDestLatitude"
+	GPSDestLongitudeRef           = "GPSDestLongitudeRef"
+	GPSDestLongitude              = "GPSDestLongitude"
+	GPSDestBearingRef             = "GPSDestBearingRef"
+	GPSDestBearing                = "GPSDestBearing"
+	GPSDestDistanceRef            = "GPSDestDistanceRef"
+	GPSDestDistance               = "GPSDestDistance"
+	GPSProcessingMethod           = "GPSProcessingMethod"
+	GPSAreaInformation            = "GPSAreaInformation"
+	GPSDateStamp                  = "GPSDateStamp"
+	GPSDifferential               = "GPSDifferential"
+)
+
+// interoperability fields
+const (
+	InteroperabilityIndex FieldName = "InteroperabilityIndex"
+)
+
+var exifFields = map[uint16]FieldName{
+	/////////////////////////////////////
+	////////// IFD 0 ////////////////////
+	/////////////////////////////////////
+
+	// image data structure for the thumbnail
+	0x0100: ImageWidth,
+	0x0101: ImageLength,
+	0x0102: BitsPerSample,
+	0x0103: Compression,
+	0x0106: PhotometricInterpretation,
+	0x0112: Orientation,
+	0x0115: SamplesPerPixel,
+	0x011C: PlanarConfiguration,
+	0x0212: YCbCrSubSampling,
+	0x0213: YCbCrPositioning,
+	0x011A: XResolution,
+	0x011B: YResolution,
+	0x0128: ResolutionUnit,
+
+	// Other tags
+	0x0132: DateTime,
+	0x010E: ImageDescription,
+	0x010F: Make,
+	0x0110: Model,
+	0x0131: Software,
+	0x013B: Artist,
+	0x8298: Copyright,
+
+	// private tags
+	exifPointer: ExifIFDPointer,
+
+	/////////////////////////////////////
+	////////// Exif sub IFD /////////////
+	/////////////////////////////////////
+
+	gpsPointer:     GPSInfoIFDPointer,
+	interopPointer: InteroperabilityIFDPointer,
+
+	0x9000: ExifVersion,
+	0xA000: FlashpixVersion,
+
+	0xA001: ColorSpace,
+
+	0x9101: ComponentsConfiguration,
+	0x9102: CompressedBitsPerPixel,
+	0xA002: PixelXDimension,
+	0xA003: PixelYDimension,
+
+	0x927C: MakerNote,
+	0x9286: UserComment,
+
+	0xA004: RelatedSoundFile,
+	0x9003: DateTimeOriginal,
+	0x9004: DateTimeDigitized,
+	0x9290: SubSecTime,
+	0x9291: SubSecTimeOriginal,
+	0x9292: SubSecTimeDigitized,
+
+	0xA420: ImageUniqueID,
+
+	// picture conditions
+	0x829A: ExposureTime,
+	0x829D: FNumber,
+	0x8822: ExposureProgram,
+	0x8824: SpectralSensitivity,
+	0x8827: ISOSpeedRatings,
+	0x8828: OECF,
+	0x9201: ShutterSpeedValue,
+	0x9202: ApertureValue,
+	0x9203: BrightnessValue,
+	0x9204: ExposureBiasValue,
+	0x9205: MaxApertureValue,
+	0x9206: SubjectDistance,
+	0x9207: MeteringMode,
+	0x9208: LightSource,
+	0x9209: Flash,
+	0x920A: FocalLength,
+	0x9214: SubjectArea,
+	0xA20B: FlashEnergy,
+	0xA20C: SpatialFrequencyResponse,
+	0xA20E: FocalPlaneXResolution,
+	0xA20F: FocalPlaneYResolution,
+	0xA210: FocalPlaneResolutionUnit,
+	0xA214: SubjectLocation,
+	0xA215: ExposureIndex,
+	0xA217: SensingMethod,
+	0xA300: FileSource,
+	0xA301: SceneType,
+	0xA302: CFAPattern,
+	0xA401: CustomRendered,
+	0xA402: ExposureMode,
+	0xA403: WhiteBalance,
+	0xA404: DigitalZoomRatio,
+	0xA405: FocalLengthIn35mmFilm,
+	0xA406: SceneCaptureType,
+	0xA407: GainControl,
+	0xA408: Contrast,
+	0xA409: Saturation,
+	0xA40A: Sharpness,
+	0xA40B: DeviceSettingDescription,
+	0xA40C: SubjectDistanceRange,
+	0xA433: LensMake,
+	0xA434: LensModel,
+}
+
+var gpsFields = map[uint16]FieldName{
+	/////////////////////////////////////
+	//// GPS sub-IFD ////////////////////
+	/////////////////////////////////////
+	0x0:  GPSVersionID,
+	0x1:  GPSLatitudeRef,
+	0x2:  GPSLatitude,
+	0x3:  GPSLongitudeRef,
+	0x4:  GPSLongitude,
+	0x5:  GPSAltitudeRef,
+	0x6:  GPSAltitude,
+	0x7:  GPSTimeStamp,
+	0x8:  GPSSatelites,
+	0x9:  GPSStatus,
+	0xA:  GPSMeasureMode,
+	0xB:  GPSDOP,
+	0xC:  GPSSpeedRef,
+	0xD:  GPSSpeed,
+	0xE:  GPSTrackRef,
+	0xF:  GPSTrack,
+	0x10: GPSImgDirectionRef,
+	0x11: GPSImgDirection,
+	0x12: GPSMapDatum,
+	0x13: GPSDestLatitudeRef,
+	0x14: GPSDestLatitude,
+	0x15: GPSDestLongitudeRef,
+	0x16: GPSDestLongitude,
+	0x17: GPSDestBearingRef,
+	0x18: GPSDestBearing,
+	0x19: GPSDestDistanceRef,
+	0x1A: GPSDestDistance,
+	0x1B: GPSProcessingMethod,
+	0x1C: GPSAreaInformation,
+	0x1D: GPSDateStamp,
+	0x1E: GPSDifferential,
+}
+
+var interopFields = map[uint16]FieldName{
+	/////////////////////////////////////
+	//// Interoperability sub-IFD ///////
+	/////////////////////////////////////
+	0x1: InteroperabilityIndex,
+}
+
+var thumbnailFields = map[uint16]FieldName{
+	0x0201: ThumbJPEGInterchangeFormat,
+	0x0202: ThumbJPEGInterchangeFormatLength,
+}

Godeps/_workspace/src/github.com/rwcarlsen/goexif/exif/regen_regress.go

@@ -0,0 +1,79 @@
+// +build ignore
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/rwcarlsen/goexif/exif"
+	"github.com/rwcarlsen/goexif/tiff"
+)
+
+func main() {
+	flag.Parse()
+	fname := flag.Arg(0)
+
+	dst, err := os.Create(fname)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer dst.Close()
+
+	dir, err := os.Open("samples")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer dir.Close()
+
+	names, err := dir.Readdirnames(0)
+	if err != nil {
+		log.Fatal(err)
+	}
+	for i, name := range names {
+		names[i] = filepath.Join("samples", name)
+	}
+	makeExpected(names, dst)
+}
+
+func makeExpected(files []string, w io.Writer) {
+	fmt.Fprintf(w, "package exif\n\n")
+	fmt.Fprintf(w, "var regressExpected = map[string]map[FieldName]string{\n")
+
+	for _, name := range files {
+		f, err := os.Open(name)
+		if err != nil {
+			continue
+		}
+
+		x, err := exif.Decode(f)
+		if err != nil {
+			f.Close()
+			continue
+		}
+
+		fmt.Fprintf(w, "\"%v\": map[FieldName]string{\n", filepath.Base(name))
+		x.Walk(&regresswalk{w})
+		fmt.Fprintf(w, "},\n")
+		f.Close()
+	}
+	fmt.Fprintf(w, "}")
+}
+
+type regresswalk struct {
+	wr io.Writer
+}
+
+func (w *regresswalk) Walk(name exif.FieldName, tag *tiff.Tag) error {
+	if strings.HasPrefix(string(name), exif.UnknownPrefix) {
+		fmt.Fprintf(w.wr, "\"%v\": `%v`,\n", name, tag.String())
+	} else {
+		fmt.Fprintf(w.wr, "%v: `%v`,\n", name, tag.String())
+	}
+	return nil
+}

Godeps/_workspace/src/github.com/rwcarlsen/goexif/tiff/tag.go

@@ -0,0 +1,438 @@
+package tiff
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"math/big"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+// Format specifies the Go type equivalent used to represent the basic
+// tiff data types.
+type Format int
+
+const (
+	IntVal Format = iota
+	FloatVal
+	RatVal
+	StringVal
+	UndefVal
+	OtherVal
+)
+
+var ErrShortReadTagValue = errors.New("tiff: short read of tag value")
+
+var formatNames = map[Format]string{
+	IntVal:    "int",
+	FloatVal:  "float",
+	RatVal:    "rational",
+	StringVal: "string",
+	UndefVal:  "undefined",
+	OtherVal:  "other",
+}
+
+// DataType represents the basic tiff tag data types.
+type DataType uint16
+
+const (
+	DTByte      DataType = 1
+	DTAscii              = 2
+	DTShort              = 3
+	DTLong               = 4
+	DTRational           = 5
+	DTSByte              = 6
+	DTUndefined          = 7
+	DTSShort             = 8
+	DTSLong              = 9
+	DTSRational          = 10
+	DTFloat              = 11
+	DTDouble             = 12
+)
+
+var typeNames = map[DataType]string{
+	DTByte:      "byte",
+	DTAscii:     "ascii",
+	DTShort:     "short",
+	DTLong:      "long",
+	DTRational:  "rational",
+	DTSByte:     "signed byte",
+	DTUndefined: "undefined",
+	DTSShort:    "signed short",
+	DTSLong:     "signed long",
+	DTSRational: "signed rational",
+	DTFloat:     "float",
+	DTDouble:    "double",
+}
+
+// typeSize specifies the size in bytes of each type.
+var typeSize = map[DataType]uint32{
+	DTByte:      1,
+	DTAscii:     1,
+	DTShort:     2,
+	DTLong:      4,
+	DTRational:  8,
+	DTSByte:     1,
+	DTUndefined: 1,
+	DTSShort:    2,
+	DTSLong:     4,
+	DTSRational: 8,
+	DTFloat:     4,
+	DTDouble:    8,
+}
+
+// Tag reflects the parsed content of a tiff IFD tag.
+type Tag struct {
+	// Id is the 2-byte tiff tag identifier.
+	Id uint16
+	// Type is an integer (1 through 12) indicating the tag value's data type.
+	Type DataType
+	// Count is the number of type Type stored in the tag's value (i.e. the
+	// tag's value is an array of type Type and length Count).
+	Count uint32
+	// Val holds the bytes that represent the tag's value.
+	Val []byte
+	// ValOffset holds byte offset of the tag value w.r.t. the beginning of the
+	// reader it was decoded from. Zero if the tag value fit inside the offset
+	// field.
+	ValOffset uint32
+
+	order     binary.ByteOrder
+	intVals   []int64
+	floatVals []float64
+	ratVals   [][]int64
+	strVal    string
+	format    Format
+}
+
+// DecodeTag parses a tiff-encoded IFD tag from r and returns a Tag object. The
+// first read from r should be the first byte of the tag. ReadAt offsets should
+// generally be relative to the beginning of the tiff structure (not relative
+// to the beginning of the tag).
+func DecodeTag(r ReadAtReader, order binary.ByteOrder) (*Tag, error) {
+	t := new(Tag)
+	t.order = order
+
+	err := binary.Read(r, order, &t.Id)
+	if err != nil {
+		return nil, errors.New("tiff: tag id read failed: " + err.Error())
+	}
+
+	err = binary.Read(r, order, &t.Type)
+	if err != nil {
+		return nil, errors.New("tiff: tag type read failed: " + err.Error())
+	}
+
+	err = binary.Read(r, order, &t.Count)
+	if err != nil {
+		return nil, errors.New("tiff: tag component count read failed: " + err.Error())
+	}
+
+	// There seems to be a relatively common corrupt tag which has a Count of
+	// MaxUint32. This is probably not a valid value, so return early.
+	if t.Count == 1<<32-1 {
+		return t, errors.New("invalid Count offset in tag")
+	}
+
+	valLen := typeSize[t.Type] * t.Count
+	if valLen == 0 {
+		return t, errors.New("zero length tag value")
+	}
+
+	if valLen > 4 {
+		binary.Read(r, order, &t.ValOffset)
+
+		// Use a bytes.Buffer so we don't allocate a huge slice if the tag
+		// is corrupt.
+		var buff bytes.Buffer
+		sr := io.NewSectionReader(r, int64(t.ValOffset), int64(valLen))
+		n, err := io.Copy(&buff, sr)
+		if err != nil {
+			return t, errors.New("tiff: tag value read failed: " + err.Error())
+		} else if n != int64(valLen) {
+			return t, ErrShortReadTagValue
+		}
+		t.Val = buff.Bytes()
+
+	} else {
+		val := make([]byte, valLen)
+		if _, err = io.ReadFull(r, val); err != nil {
+			return t, errors.New("tiff: tag offset read failed: " + err.Error())
+		}
+		// ignore padding.
+		if _, err = io.ReadFull(r, make([]byte, 4-valLen)); err != nil {
+			return t, errors.New("tiff: tag offset read failed: " + err.Error())
+		}
+
+		t.Val = val
+	}
+
+	return t, t.convertVals()
+}
+
+func (t *Tag) convertVals() error {
+	r := bytes.NewReader(t.Val)
+
+	switch t.Type {
+	case DTAscii:
+		if len(t.Val) > 0 {
+			t.strVal = string(t.Val[:len(t.Val)-1]) // ignore the last byte (NULL).
+		}
+	case DTByte:
+		var v uint8
+		t.intVals = make([]int64, int(t.Count))
+		for i := range t.intVals {
+			err := binary.Read(r, t.order, &v)
+			if err != nil {
+				return err
+			}
+			t.intVals[i] = int64(v)
+		}
+	case DTShort:
+		var v uint16
+		t.intVals = make([]int64, int(t.Count))
+		for i := range t.intVals {
+			err := binary.Read(r, t.order, &v)
+			if err != nil {
+				return err
+			}
+			t.intVals[i] = int64(v)
+		}
+	case DTLong:
+		var v uint32
+		t.intVals = make([]int64, int(t.Count))
+		for i := range t.intVals {
+			err := binary.Read(r, t.order, &v)
+			if err != nil {
+				return err
+			}
+			t.intVals[i] = int64(v)
+		}
+	case DTSByte:
+		var v int8
+		t.intVals = make([]int64, int(t.Count))
+		for i := range t.intVals {
+			err := binary.Read(r, t.order, &v)
+			if err != nil {
+				return err
+			}
+			t.intVals[i] = int64(v)
+		}
+	case DTSShort:
+		var v int16
+		t.intVals = make([]int64, int(t.Count))
+		for i := range t.intVals {
+			err := binary.Read(r, t.order, &v)
+			if err != nil {
+				return err
+			}
+			t.intVals[i] = int64(v)
+		}
+	case DTSLong:
+		var v int32
+		t.intVals = make([]int64, int(t.Count))
+		for i := range t.intVals {
+			err := binary.Read(r, t.order, &v)
+			if err != nil {
+				return err
+			}
+			t.intVals[i] = int64(v)
+		}
+	case DTRational:
+		t.ratVals = make([][]int64, int(t.Count))
+		for i := range t.ratVals {
+			var n, d uint32
+			err := binary.Read(r, t.order, &n)
+			if err != nil {
+				return err
+			}
+			err = binary.Read(r, t.order, &d)
+			if err != nil {
+				return err
+			}
+			t.ratVals[i] = []int64{int64(n), int64(d)}
+		}
+	case DTSRational:
+		t.ratVals = make([][]int64, int(t.Count))
+		for i := range t.ratVals {
+			var n, d int32
+			err := binary.Read(r, t.order, &n)
+			if err != nil {
+				return err
+			}
+			err = binary.Read(r, t.order, &d)
+			if err != nil {
+				return err
+			}
+			t.ratVals[i] = []int64{int64(n), int64(d)}
+		}
+	case DTFloat: // float32
+		t.floatVals = make([]float64, int(t.Count))
+		for i := range t.floatVals {
+			var v float32
+			err := binary.Read(r, t.order, &v)
+			if err != nil {
+				return err
+			}
+			t.floatVals[i] = float64(v)
+		}
+	case DTDouble:
+		t.floatVals = make([]float64, int(t.Count))
+		for i := range t.floatVals {
+			var u float64
+			err := binary.Read(r, t.order, &u)
+			if err != nil {
+				return err
+			}
+			t.floatVals[i] = u
+		}
+	}
+
+	switch t.Type {
+	case DTByte, DTShort, DTLong, DTSByte, DTSShort, DTSLong:
+		t.format = IntVal
+	case DTRational, DTSRational:
+		t.format = RatVal
+	case DTFloat, DTDouble:
+		t.format = FloatVal
+	case DTAscii:
+		t.format = StringVal
+	case DTUndefined:
+		t.format = UndefVal
+	default:
+		t.format = OtherVal
+	}
+
+	return nil
+}
+
+// Format returns a value indicating which method can be called to retrieve the
+// tag's value properly typed (e.g. integer, rational, etc.).
+func (t *Tag) Format() Format { return t.format }
+
+func (t *Tag) typeErr(to Format) error {
+	return &wrongFmtErr{typeNames[t.Type], formatNames[to]}
+}
+
+// Rat returns the tag's i'th value as a rational number. It returns a nil and
+// an error if this tag's Format is not RatVal.  It panics for zero deminators
+// or if i is out of range.
+func (t *Tag) Rat(i int) (*big.Rat, error) {
+	n, d, err := t.Rat2(i)
+	if err != nil {
+		return nil, err
+	}
+	return big.NewRat(n, d), nil
+}
+
+// Rat2 returns the tag's i'th value as a rational number represented by a
+// numerator-denominator pair. It returns an error if the tag's Format is not
+// RatVal. It panics if i is out of range.
+func (t *Tag) Rat2(i int) (num, den int64, err error) {
+	if t.format != RatVal {
+		return 0, 0, t.typeErr(RatVal)
+	}
+	return t.ratVals[i][0], t.ratVals[i][1], nil
+}
+
+// Int64 returns the tag's i'th value as an integer. It returns an error if the
+// tag's Format is not IntVal. It panics if i is out of range.
+func (t *Tag) Int64(i int) (int64, error) {
+	if t.format != IntVal {
+		return 0, t.typeErr(IntVal)
+	}
+	return t.intVals[i], nil
+}
+
+// Int returns the tag's i'th value as an integer. It returns an error if the
+// tag's Format is not IntVal. It panics if i is out of range.
+func (t *Tag) Int(i int) (int, error) {
+	if t.format != IntVal {
+		return 0, t.typeErr(IntVal)
+	}
+	return int(t.intVals[i]), nil
+}
+
+// Float returns the tag's i'th value as a float. It returns an error if the
+// tag's Format is not IntVal.  It panics if i is out of range.
+func (t *Tag) Float(i int) (float64, error) {
+	if t.format != FloatVal {
+		return 0, t.typeErr(FloatVal)
+	}
+	return t.floatVals[i], nil
+}
+
+// StringVal returns the tag's value as a string. It returns an error if the
+// tag's Format is not StringVal. It panics if i is out of range.
+func (t *Tag) StringVal() (string, error) {
+	if t.format != StringVal {
+		return "", t.typeErr(StringVal)
+	}
+	return t.strVal, nil
+}
+
+// String returns a nicely formatted version of the tag.
+func (t *Tag) String() string {
+	data, err := t.MarshalJSON()
+	if err != nil {
+		return "ERROR: " + err.Error()
+	}
+
+	if t.Count == 1 {
+		return strings.Trim(fmt.Sprintf("%s", data), "[]")
+	}
+	return fmt.Sprintf("%s", data)
+}
+
+func (t *Tag) MarshalJSON() ([]byte, error) {
+	switch t.format {
+	case StringVal, UndefVal:
+		return nullString(t.Val), nil
+	case OtherVal:
+		return []byte(fmt.Sprintf("unknown tag type '%v'", t.Type)), nil
+	}
+
+	rv := []string{}
+	for i := 0; i < int(t.Count); i++ {
+		switch t.format {
+		case RatVal:
+			n, d, _ := t.Rat2(i)
+			rv = append(rv, fmt.Sprintf(`"%v/%v"`, n, d))
+		case FloatVal:
+			v, _ := t.Float(i)
+			rv = append(rv, fmt.Sprintf("%v", v))
+		case IntVal:
+			v, _ := t.Int(i)
+			rv = append(rv, fmt.Sprintf("%v", v))
+		}
+	}
+	return []byte(fmt.Sprintf(`[%s]`, strings.Join(rv, ","))), nil
+}
+
+func nullString(in []byte) []byte {
+	rv := bytes.Buffer{}
+	rv.WriteByte('"')
+	for _, b := range in {
+		if unicode.IsPrint(rune(b)) {
+			rv.WriteByte(b)
+		}
+	}
+	rv.WriteByte('"')
+	rvb := rv.Bytes()
+	if utf8.Valid(rvb) {
+		return rvb
+	}
+	return []byte(`""`)
+}
+
+type wrongFmtErr struct {
+	From, To string
+}
+
+func (e *wrongFmtErr) Error() string {
+	return fmt.Sprintf("cannot convert tag type '%v' into '%v'", e.From, e.To)
+}

Godeps/_workspace/src/github.com/rwcarlsen/goexif/tiff/tiff.go

@@ -0,0 +1,153 @@
+// Package tiff implements TIFF decoding as defined in TIFF 6.0 specification at
+// http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf
+package tiff
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+)
+
+// ReadAtReader is used when decoding Tiff tags and directories
+type ReadAtReader interface {
+	io.Reader
+	io.ReaderAt
+}
+
+// Tiff provides access to a decoded tiff data structure.
+type Tiff struct {
+	// Dirs is an ordered slice of the tiff's Image File Directories (IFDs).
+	// The IFD at index 0 is IFD0.
+	Dirs []*Dir
+	// The tiff's byte-encoding (i.e. big/little endian).
+	Order binary.ByteOrder
+}
+
+// Decode parses tiff-encoded data from r and returns a Tiff struct that
+// reflects the structure and content of the tiff data. The first read from r
+// should be the first byte of the tiff-encoded data and not necessarily the
+// first byte of an os.File object.
+func Decode(r io.Reader) (*Tiff, error) {
+	data, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, errors.New("tiff: could not read data")
+	}
+	buf := bytes.NewReader(data)
+
+	t := new(Tiff)
+
+	// read byte order
+	bo := make([]byte, 2)
+	if _, err = io.ReadFull(buf, bo); err != nil {
+		return nil, errors.New("tiff: could not read tiff byte order")
+	}
+	if string(bo) == "II" {
+		t.Order = binary.LittleEndian
+	} else if string(bo) == "MM" {
+		t.Order = binary.BigEndian
+	} else {
+		return nil, errors.New("tiff: could not read tiff byte order")
+	}
+
+	// check for special tiff marker
+	var sp int16
+	err = binary.Read(buf, t.Order, &sp)
+	if err != nil || 42 != sp {
+		return nil, errors.New("tiff: could not find special tiff marker")
+	}
+
+	// load offset to first IFD
+	var offset int32
+	err = binary.Read(buf, t.Order, &offset)
+	if err != nil {
+		return nil, errors.New("tiff: could not read offset to first IFD")
+	}
+
+	// load IFD's
+	var d *Dir
+	prev := offset
+	for offset != 0 {
+		// seek to offset
+		_, err := buf.Seek(int64(offset), 0)
+		if err != nil {
+			return nil, errors.New("tiff: seek to IFD failed")
+		}
+
+		if buf.Len() == 0 {
+			return nil, errors.New("tiff: seek offset after EOF")
+		}
+
+		// load the dir
+		d, offset, err = DecodeDir(buf, t.Order)
+		if err != nil {
+			return nil, err
+		}
+
+		if offset == prev {
+			return nil, errors.New("tiff: recursive IFD")
+		}
+		prev = offset
+
+		t.Dirs = append(t.Dirs, d)
+	}
+
+	return t, nil
+}
+
+func (tf *Tiff) String() string {
+	var buf bytes.Buffer
+	fmt.Fprint(&buf, "Tiff{")
+	for _, d := range tf.Dirs {
+		fmt.Fprintf(&buf, "%s, ", d.String())
+	}
+	fmt.Fprintf(&buf, "}")
+	return buf.String()
+}
+
+// Dir provides access to the parsed content of a tiff Image File Directory (IFD).
+type Dir struct {
+	Tags []*Tag
+}
+
+// DecodeDir parses a tiff-encoded IFD from r and returns a Dir object.  offset
+// is the offset to the next IFD.  The first read from r should be at the first
+// byte of the IFD. ReadAt offsets should generally be relative to the
+// beginning of the tiff structure (not relative to the beginning of the IFD).
+func DecodeDir(r ReadAtReader, order binary.ByteOrder) (d *Dir, offset int32, err error) {
+	d = new(Dir)
+
+	// get num of tags in ifd
+	var nTags int16
+	err = binary.Read(r, order, &nTags)
+	if err != nil {
+		return nil, 0, errors.New("tiff: failed to read IFD tag count: " + err.Error())
+	}
+
+	// load tags
+	for n := 0; n < int(nTags); n++ {
+		t, err := DecodeTag(r, order)
+		if err != nil {
+			return nil, 0, err
+		}
+		d.Tags = append(d.Tags, t)
+	}
+
+	// get offset to next ifd
+	err = binary.Read(r, order, &offset)
+	if err != nil {
+		return nil, 0, errors.New("tiff: falied to read offset to next IFD: " + err.Error())
+	}
+
+	return d, offset, nil
+}
+
+func (d *Dir) String() string {
+	s := "Dir{"
+	for _, t := range d.Tags {
+		s += t.String() + ", "
+	}
+	return s + "}"
+}

Godeps/_workspace/src/github.com/rwcarlsen/goexif/tiff/tiff_test.go

@@ -0,0 +1,235 @@
+package tiff
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/hex"
+	"flag"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+var dataDir = flag.String("test_data_dir", ".", "Directory where the data files for testing are located")
+
+type input struct {
+	tgId   string
+	tpe    string
+	nVals  string
+	offset string
+	val    string
+}
+
+type output struct {
+	id    uint16
+	typ   DataType
+	count uint32
+	val   []byte
+}
+
+type tagTest struct {
+	big    input // big endian
+	little input // little endian
+	out    output
+}
+
+///////////////////////////////////////////////
+//// Big endian Tests /////////////////////////
+///////////////////////////////////////////////
+var set1 = []tagTest{
+	//////////// string type //////////////
+	tagTest{
+		//   {"TgId", "TYPE", "N-VALUES", "OFFSET--", "VAL..."},
+		input{"0003", "0002", "00000002", "11000000", ""},
+		input{"0300", "0200", "02000000", "11000000", ""},
+		output{0x0003, DataType(0x0002), 0x0002, []byte{0x11, 0x00}},
+	},
+	tagTest{
+		input{"0001", "0002", "00000006", "00000012", "111213141516"},
+		input{"0100", "0200", "06000000", "12000000", "111213141516"},
+		output{0x0001, DataType(0x0002), 0x0006, []byte{0x11, 0x12, 0x13, 0x14, 0x15, 0x16}},
+	},
+	//////////// int (1-byte) type ////////////////
+	tagTest{
+		input{"0001", "0001", "00000001", "11000000", ""},
+		input{"0100", "0100", "01000000", "11000000", ""},
+		output{0x0001, DataType(0x0001), 0x0001, []byte{0x11}},
+	},
+	tagTest{
+		input{"0001", "0001", "00000005", "00000010", "1112131415"},
+		input{"0100", "0100", "05000000", "10000000", "1112131415"},
+		output{0x0001, DataType(0x0001), 0x0005, []byte{0x11, 0x12, 0x13, 0x14, 0x15}},
+	},
+	tagTest{
+		input{"0001", "0006", "00000001", "11000000", ""},
+		input{"0100", "0600", "01000000", "11000000", ""},
+		output{0x0001, DataType(0x0006), 0x0001, []byte{0x11}},
+	},
+	tagTest{
+		input{"0001", "0006", "00000005", "00000010", "1112131415"},
+		input{"0100", "0600", "05000000", "10000000", "1112131415"},
+		output{0x0001, DataType(0x0006), 0x0005, []byte{0x11, 0x12, 0x13, 0x14, 0x15}},
+	},
+	//////////// int (2-byte) types ////////////////
+	tagTest{
+		input{"0001", "0003", "00000002", "11111212", ""},
+		input{"0100", "0300", "02000000", "11111212", ""},
+		output{0x0001, DataType(0x0003), 0x0002, []byte{0x11, 0x11, 0x12, 0x12}},
+	},
+	tagTest{
+		input{"0001", "0003", "00000003", "00000010", "111213141516"},
+		input{"0100", "0300", "03000000", "10000000", "111213141516"},
+		output{0x0001, DataType(0x0003), 0x0003, []byte{0x11, 0x12, 0x13, 0x14, 0x15, 0x16}},
+	},
+	tagTest{
+		input{"0001", "0008", "00000001", "11120000", ""},
+		input{"0100", "0800", "01000000", "11120000", ""},
+		output{0x0001, DataType(0x0008), 0x0001, []byte{0x11, 0x12}},
+	},
+	tagTest{
+		input{"0001", "0008", "00000003", "00000100", "111213141516"},
+		input{"0100", "0800", "03000000", "00100000", "111213141516"},
+		output{0x0001, DataType(0x0008), 0x0003, []byte{0x11, 0x12, 0x13, 0x14, 0x15, 0x16}},
+	},
+	//////////// int (4-byte) types ////////////////
+	tagTest{
+		input{"0001", "0004", "00000001", "11121314", ""},
+		input{"0100", "0400", "01000000", "11121314", ""},
+		output{0x0001, DataType(0x0004), 0x0001, []byte{0x11, 0x12, 0x13, 0x14}},
+	},
+	tagTest{
+		input{"0001", "0004", "00000002", "00000010", "1112131415161718"},
+		input{"0100", "0400", "02000000", "10000000", "1112131415161718"},
+		output{0x0001, DataType(0x0004), 0x0002, []byte{0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18}},
+	},
+	tagTest{
+		input{"0001", "0009", "00000001", "11121314", ""},
+		input{"0100", "0900", "01000000", "11121314", ""},
+		output{0x0001, DataType(0x0009), 0x0001, []byte{0x11, 0x12, 0x13, 0x14}},
+	},
+	tagTest{
+		input{"0001", "0009", "00000002", "00000011", "1112131415161819"},
+		input{"0100", "0900", "02000000", "11000000", "1112131415161819"},
+		output{0x0001, DataType(0x0009), 0x0002, []byte{0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x18, 0x19}},
+	},
+	//////////// rational types ////////////////////
+	tagTest{
+		input{"0001", "0005", "00000001", "00000010", "1112131415161718"},
+		input{"0100", "0500", "01000000", "10000000", "1112131415161718"},
+		output{0x0001, DataType(0x0005), 0x0001, []byte{0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18}},
+	},
+	tagTest{
+		input{"0001", "000A", "00000001", "00000011", "1112131415161819"},
+		input{"0100", "0A00", "01000000", "11000000", "1112131415161819"},
+		output{0x0001, DataType(0x000A), 0x0001, []byte{0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x18, 0x19}},
+	},
+	//////////// float types ///////////////////////
+	tagTest{
+		input{"0001", "0005", "00000001", "00000010", "1112131415161718"},
+		input{"0100", "0500", "01000000", "10000000", "1112131415161718"},
+		output{0x0001, DataType(0x0005), 0x0001, []byte{0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18}},
+	},
+	tagTest{
+		input{"0101", "000A", "00000001", "00000011", "1112131415161819"},
+		input{"0101", "0A00", "01000000", "11000000", "1112131415161819"},
+		output{0x0101, DataType(0x000A), 0x0001, []byte{0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x18, 0x19}},
+	},
+}
+
+func TestDecodeTag(t *testing.T) {
+	for i, tst := range set1 {
+		testSingle(t, binary.BigEndian, tst.big, tst.out, i)
+		testSingle(t, binary.LittleEndian, tst.little, tst.out, i)
+	}
+}
+
+func testSingle(t *testing.T, order binary.ByteOrder, in input, out output, i int) {
+	data := buildInput(in, order)
+	buf := bytes.NewReader(data)
+	tg, err := DecodeTag(buf, order)
+	if err != nil {
+		t.Errorf("(%v) tag %v%+v decode failed: %v", order, i, in, err)
+		return
+	}
+
+	if tg.Id != out.id {
+		t.Errorf("(%v) tag %v id decode: expected %v, got %v", order, i, out.id, tg.Id)
+	}
+	if tg.Type != out.typ {
+		t.Errorf("(%v) tag %v type decode: expected %v, got %v", order, i, out.typ, tg.Type)
+	}
+	if tg.Count != out.count {
+		t.Errorf("(%v) tag %v component count decode: expected %v, got %v", order, i, out.count, tg.Count)
+	}
+	if !bytes.Equal(tg.Val, out.val) {
+		t.Errorf("(%v) tag %v value decode: expected %v, got %v", order, i, out.val, tg.Val)
+	}
+}
+
+// buildInputBig creates a byte-slice based on big-endian ordered input
+func buildInput(in input, order binary.ByteOrder) []byte {
+	data := make([]byte, 0)
+	d, _ := hex.DecodeString(in.tgId)
+	data = append(data, d...)
+	d, _ = hex.DecodeString(in.tpe)
+	data = append(data, d...)
+	d, _ = hex.DecodeString(in.nVals)
+	data = append(data, d...)
+	d, _ = hex.DecodeString(in.offset)
+	data = append(data, d...)
+
+	if in.val != "" {
+		off := order.Uint32(d)
+		for i := 0; i < int(off)-12; i++ {
+			data = append(data, 0xFF)
+		}
+
+		d, _ = hex.DecodeString(in.val)
+		data = append(data, d...)
+	}
+
+	return data
+}
+
+func TestDecode(t *testing.T) {
+	name := filepath.Join(*dataDir, "sample1.tif")
+	f, err := os.Open(name)
+	if err != nil {
+		t.Fatalf("%v\n", err)
+	}
+
+	tif, err := Decode(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Log(tif)
+}
+
+func TestDecodeTag_blob(t *testing.T) {
+	buf := bytes.NewReader(data())
+	buf.Seek(10, 1)
+	tg, err := DecodeTag(buf, binary.LittleEndian)
+	if err != nil {
+		t.Fatalf("tag decode failed: %v", err)
+	}
+
+	t.Logf("tag: %v+\n", tg)
+	n, d, err := tg.Rat2(0)
+	if err != nil {
+		t.Fatalf("tag decoded wrong type: %v", err)
+	}
+	t.Logf("tag rat val: %v/%v\n", n, d)
+}
+
+func data() []byte {
+	s1 := "49492A000800000002001A0105000100"
+	s1 += "00002600000069870400010000001102"
+	s1 += "0000000000004800000001000000"
+
+	dat, err := hex.DecodeString(s1)
+	if err != nil {
+		panic("invalid string fixture")
+	}
+	return dat
+}