Add TIFF support, XMP support for JPEGs etc.

imagedecoder_jpg.go

@@ -2,96 +2,119 @@ package imagemeta
 
 import (
 	"encoding/binary"
+	"io"
 )
 
 type imageDecoderJPEG struct {
 	*baseStreamingDecoder
 }
 
-func (e *imageDecoderJPEG) decode() (err error) {
+func (e *imageDecoderJPEG) decode() error {
 	// JPEG SOI marker.
-	var soi uint16
-	if soi, err = e.read2E(); err != nil {
+	soi, err := e.read2E()
+	if err != nil {
 		return nil
 	}
+
 	if soi != markerSOI {
-		return
+		return nil
 	}
 
-	findMarker := func(markerToFind uint16) int {
-		for {
-			var marker, length uint16
-			if marker, err = e.read2E(); err != nil {
-				return -1
-			}
-			if length, err = e.read2E(); err != nil {
-				return -1
-			}
+	// These are the sources we support.
+	sourceSet := TagSourceEXIF | TagSourceIPTC | TagSourceXMP
+	// Remove sources that are not requested.
+	sourceSet = sourceSet & e.opts.Sources
 
-			// All JPEG markers begin with 0xff.
-			if marker>>8 != 0xff {
-				return -1
-			}
+	for {
+		if sourceSet.IsZero() {
+			// Done.
+			return nil
+		}
+		marker := e.read2()
+		if e.isEOF {
+			return nil
+		}
 
-			if marker == markerToFind {
-				return int(length)
-			}
+		if marker == 0 {
+			continue
+		}
 
-			if length < 2 {
-				return -1
-			}
+		if marker == markerSOS {
+			// Start of scan. We're done.
+			return nil
+		}
 
-			e.skip(int64(length - 2))
+		// Read the 16-bit length of the segment. The value includes the 2 bytes for the
+		// length itself, so we subtract 2 to get the number of remaining bytes.
+		length := e.read2()
+		if length < 2 {
+			return ErrInvalidFormat
 		}
-	}
+		length -= 2
 
-	if e.opts.Sources.Has(TagSourceEXIF) {
-		pos := e.pos()
-		if length := findMarker(markerAPP1); length > 0 {
-			err := func() error {
-				r, err := e.bufferedReader(length)
-				if err != nil {
-					return err
-				}
-				defer r.Close()
-				exifr := newMetaDecoderEXIF(r, e.opts.HandleTag)
-
-				header := exifr.read4()
-				if header != exifHeader {
-					return err
-				}
-				exifr.skip(2)
-				if err := exifr.decode(); err != nil {
-					return err
-				}
-				return nil
-
-			}()
-
-			if err != nil {
+		if marker == markerApp1EXIF && sourceSet.Has(TagSourceEXIF) {
+			sourceSet = sourceSet.Remove(TagSourceEXIF)
+			if err := e.handleEXIF(int(length)); err != nil {
 				return err
 			}
+			continue
+		}
 
+		if marker == markerApp13 && sourceSet.Has(TagSourceIPTC) {
+			sourceSet = sourceSet.Remove(TagSourceIPTC)
+			if err := e.handleIPTC(int(length)); err != nil {
+				return err
+			}
+			continue
 		}
-		e.seek(pos)
-	}
 
-	if e.opts.Sources.Has(TagSourceIPTC) {
-		// EXIF may be stored in a different order, but IPTC is always big-endian.
-		e.byteOrder = binary.BigEndian
-		if length := findMarker(markerApp13); length > 0 {
-			if err := func() error {
-				r, err := e.bufferedReader(length)
-				if err != nil {
-					return err
-				}
-				defer r.Close()
-				dec := newMetaDecoderIPTC(r, e.opts.HandleTag)
-				return dec.decode()
-			}(); err != nil {
+		if marker == markerrApp1XMP && sourceSet.Has(TagSourceXMP) {
+			sourceSet = sourceSet.Remove(TagSourceXMP)
+			const xmpIDLen = 29
+			if length < xmpIDLen {
+				return ErrInvalidFormat
+			}
+			e.skip(int64(xmpIDLen))
+			length -= xmpIDLen
+			r := io.LimitReader(e.r, int64(length))
+			if err := decodeXMP(r, e.opts.HandleTag); err != nil {
 				return err
 			}
+			continue
 		}
+
+		e.skip(int64(length))
+	}
+}
+
+func (e *imageDecoderJPEG) handleIPTC(length int) error {
+	// EXIF may be stored in a different order, but IPTC is always big-endian.
+	e.byteOrder = binary.BigEndian
+	r, err := e.bufferedReader(length)
+	if err != nil {
+		return err
+	}
+	defer r.Close()
+	dec := newMetaDecoderIPTC(r, e.opts.HandleTag)
+	return dec.decode()
+}
+
+func (e *imageDecoderJPEG) handleEXIF(length int) error {
+	r, err := e.bufferedReader(length)
+	if err != nil {
+		return err
+	}
+	defer r.Close()
+	exifr := newMetaDecoderEXIF(r, e.opts.HandleTag)
+
+	header := exifr.read4()
+	if header != exifHeader {
+		return err
+	}
+	exifr.skip(2)
+	if err := exifr.decode(); err != nil {
+		return err
 	}
 	return nil
+
 }

imagedecoder_png.go

@@ -4,7 +4,7 @@ type imageDecoderPNG struct {
 	*baseStreamingDecoder
 }
 
-func (e *imageDecoderPNG) decode() (err error) {
+func (e *imageDecoderPNG) decode() error {
 	// http://ftp-osl.osuosl.org/pub/libpng/documents/pngext-1.5.0.html#C.eXIf
 	// The four-byte chunk type field contains the decimal values:
 	// 101 88 73 102 (ASCII "eXIf")
@@ -19,7 +19,7 @@ func (e *imageDecoderPNG) decode() (err error) {
 	for {
 		chunkLength, typ := e.read4(), e.read4()
 
-		if typ == pngExifMarker {
+		if typ == pngEXIFMarker {
 			return func() error {
 				r, err := e.bufferedReader(int(chunkLength))
 				if err != nil {

imagedecoder_tif.go

@@ -0,0 +1,75 @@
+package imagemeta
+
+import (
+	"encoding/binary"
+	"io"
+)
+
+type imageDecoderTIF struct {
+	*baseStreamingDecoder
+}
+
+func (e *imageDecoderTIF) decode() error {
+	const (
+		xmpMarker     = 0x02bc
+		meaningOfLife = 42
+	)
+
+	// These are the sources we currently support in TIFF.
+	sourceSet := TagSourceXMP
+	// Remove sources that are not requested.
+	sourceSet = sourceSet & e.opts.Sources
+
+	if sourceSet.IsZero() {
+		// Done.
+		return nil
+	}
+
+	byteOrderTag := e.read2()
+	switch byteOrderTag {
+	case byteOrderBigEndian:
+		e.byteOrder = binary.BigEndian
+	case byteOrderLittleEndian:
+		e.byteOrder = binary.LittleEndian
+	default:
+		return ErrInvalidFormat
+	}
+
+	if id := e.read2(); id != meaningOfLife {
+		return ErrInvalidFormat
+	}
+
+	ifdOffset := e.read4()
+
+	if ifdOffset < 8 {
+		return ErrInvalidFormat
+	}
+
+	e.skip(int64(ifdOffset - 8))
+
+	entryCount := e.read2()
+
+	for i := 0; i < int(entryCount); i++ {
+		tag := e.read2()
+		// Skip type
+		e.skip(2)
+		count := e.read4()
+		valueOffset := e.read4() // Offset relative to the start of the file.
+		if tag == xmpMarker {
+			pos := e.pos()
+			e.seek(int(valueOffset))
+			r := io.LimitReader(e.r, int64(count))
+			if err := decodeXMP(r, e.opts.HandleTag); err != nil {
+				return err
+			}
+			sourceSet = sourceSet.Remove(TagSourceXMP)
+			if sourceSet.IsZero() {
+				return nil
+			}
+			e.seek(pos)
+		}
+	}
+
+	return nil
+
+}