Example #1
0
// FileTime returns the best guess of the file's creation time (or modtime).
// If the file doesn't have its own metadata indication the creation time (such as in EXIF),
// FileTime uses the modification time from the file system.
// It there was a valid EXIF but an error while trying to get a date from it,
// it logs the error and tries the other methods.
func FileTime(f io.ReaderAt) (time.Time, error) {
	var ct time.Time
	defaultTime := func() (time.Time, error) {
		if osf, ok := f.(*os.File); ok {
			fi, err := osf.Stat()
			if err != nil {
				return ct, fmt.Errorf("Failed to find a modtime: stat: %v", err)
			}
			return fi.ModTime(), nil
		}
		return ct, errors.New("All methods failed to find a creation time or modtime.")
	}

	size, ok := findSize(f)
	if !ok {
		size = 256 << 10 // enough to get the EXIF
	}
	r := io.NewSectionReader(f, 0, size)
	var tiffErr error
	ex, err := exif.Decode(r)
	if err != nil {
		tiffErr = err
		if exif.IsShortReadTagValueError(err) {
			return ct, io.ErrUnexpectedEOF
		}
		if exif.IsCriticalError(err) || exif.IsExifError(err) {
			return defaultTime()
		}
	}
	ct, err = ex.DateTime()
	if err != nil {
		return defaultTime()
	}
	// If the EXIF file only had local timezone, but it did have
	// GPS, then lookup the timezone and correct the time.
	if ct.Location() == time.Local {
		if exif.IsGPSError(tiffErr) {
			log.Printf("Invalid EXIF GPS data: %v", tiffErr)
			return ct, nil
		}
		if lat, long, err := ex.LatLong(); err == nil {
			if loc := lookupLocation(latlong.LookupZoneName(lat, long)); loc != nil {
				if t, err := exifDateTimeInLocation(ex, loc); err == nil {
					return t, nil
				}
			}
		} else if !exif.IsTagNotPresentError(err) {
			log.Printf("Invalid EXIF GPS data: %v", err)
		}
	}
	return ct, nil
}
Example #2
0
func showEXIF(file string) {
	f, err := os.Open(file)
	if err != nil {
		panic(err.Error())
	}
	defer f.Close()
	ex, err := exif.Decode(f)
	if err != nil {
		if exif.IsCriticalError(err) {
			log.Fatalf("exif.Decode, critical error: %v", err)
		}
		log.Printf("exif.Decode, warning: %v", err)
	}
	fmt.Printf("%v\n", ex)
	if exif.IsExifError(err) {
		// the error happened while decoding the EXIF sub-IFD, so as DateTime is
		// part of it, we have to assume (until there's a better "decode effort"
		// strategy in goexif) that it's not usable.
		return
	}
	ct, err := ex.DateTime()
	fmt.Printf("exif.DateTime = %v, %v\n", ct, err)
}