First take

README.md

@@ -1,3 +1,7 @@
 [![Tests on Linux, MacOS and Windows](https://github.com/bep/goexif/workflows/Test/badge.svg)](https://github.com/bep/goexif/actions?query=workflow:Test)
 [![Go Report Card](https://goreportcard.com/badge/github.com/bep/goexif)](https://goreportcard.com/report/github.com/bep/goexif)
-[![GoDoc](https://godoc.org/github.com/bep/goexif?status.svg)](https://godoc.org/github.com/bep/goexif)
+[![GoDoc](https://godoc.org/github.com/bep/goexif?status.svg)](https://godoc.org/github.com/bep/goexif)
+
+# Work in progress
+
+This is not ready, yet, but the goal is to use this as the library to read image metadata in Hugo. The existing Go libraries I have found is not maintained anymore and too complex to build on top of. The goal of this library is to be relatively small and simple, but I may prove myself wrong.

fieldsexif.go

@@ -0,0 +1,90 @@
+package goexif
+
+import "fmt"
+
+const (
+	OrientationUnspecified Orientation = iota
+	OrientationNormal
+	OrientationFlipH
+	OrientationRotate180
+	OrientationFlipV
+	OrientationTranspose
+	OrientationRotate270
+	OrientationTransverse
+	OrientationRotate90
+)
+
+const (
+	// TODO1 check usage.
+	markerSOI             = 0xffd8
+	markerAPP1            = 0xffe1
+	markerApp13           = 0xffed
+	exifPointer           = 0x8769
+	gpsPointer            = 0x8825
+	interopPointer        = 0xa005
+	exifHeader            = 0x45786966
+	byteOrderBigEndian    = 0x4d4d
+	byteOrderLittleEndian = 0x4949
+	tagOrientation        = 0x0112
+	tagDate               = 0x0132
+)
+
+var errStop = fmt.Errorf("stop")
+
+const (
+	typeUnsignedByte  exifType = 1
+	typeUnsignedAscii exifType = 2
+	typeUnsignedShort exifType = 3
+	typeUnsignedLong  exifType = 4
+	typeUnsignedRat   exifType = 5
+	typeSignedByte    exifType = 6
+	typeUndef         exifType = 7
+	typeSignedShort   exifType = 8
+	typeSignedLong    exifType = 9
+	typeSignedRat     exifType = 10
+	typeSignedFloat   exifType = 11
+	typeSignedDouble  exifType = 12
+)
+
+// Size in bytes of each type.
+var typeSize = map[exifType]uint32{
+	typeUnsignedByte:  1,
+	typeUnsignedAscii: 1,
+	typeUnsignedShort: 2,
+	typeUnsignedLong:  4,
+	typeUnsignedRat:   8,
+	typeSignedByte:    1,
+	typeUndef:         1,
+	typeSignedShort:   2,
+	typeSignedLong:    4,
+	typeSignedRat:     8,
+	typeSignedFloat:   4,
+	typeSignedDouble:  8,
+}
+
+// UnknownPrefix is used as prefix for unknown tags.
+const UnknownPrefix = "UnknownTag_"
+
+var (
+	fieldsExif      = map[uint16]string{0x100: "ImageWidth", 0x101: "ImageLength", 0x102: "BitsPerSample", 0x103: "Compression", 0x106: "PhotometricInterpretation", 0x10e: "ImageDescription", 0x10f: "Make", 0x110: "Model", 0x112: "Orientation", 0x115: "SamplesPerPixel", 0x11a: "XResolution", 0x11b: "YResolution", 0x11c: "PlanarConfiguration", 0x128: "ResolutionUnit", 0x131: "Software", 0x132: "DateTime", 0x13b: "Artist", 0x212: "YCbCrSubSampling", 0x213: "YCbCrPositioning", 0x8298: "Copyright", 0x829a: "ExposureTime", 0x829d: "FNumber", 0x8769: "ExifIFDPointer", 0x8822: "ExposureProgram", 0x8824: "SpectralSensitivity", 0x8825: "GPSInfoIFDPointer", 0x8827: "ISOSpeedRatings", 0x8828: "OECF", 0x9000: "ExifVersion", 0x9003: "DateTimeOriginal", 0x9004: "DateTimeDigitized", 0x9101: "ComponentsConfiguration", 0x9102: "CompressedBitsPerPixel", 0x9201: "ShutterSpeedValue", 0x9202: "ApertureValue", 0x9203: "BrightnessValue", 0x9204: "ExposureBiasValue", 0x9205: "MaxApertureValue", 0x9206: "SubjectDistance", 0x9207: "MeteringMode", 0x9208: "LightSource", 0x9209: "Flash", 0x920a: "FocalLength", 0x9214: "SubjectArea", 0x927c: "MakerNote", 0x9286: "UserComment", 0x9290: "SubSecTime", 0x9291: "SubSecTimeOriginal", 0x9292: "SubSecTimeDigitized", 0x9c9b: "XPTitle", 0x9c9c: "XPComment", 0x9c9d: "XPAuthor", 0x9c9e: "XPKeywords", 0x9c9f: "XPSubject", 0xa000: "FlashpixVersion", 0xa001: "ColorSpace", 0xa002: "PixelXDimension", 0xa003: "PixelYDimension", 0xa004: "RelatedSoundFile", 0xa005: "InteroperabilityIFDPointer", 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", 0xa420: "ImageUniqueID", 0xa433: "LensMake", 0xa434: "LensModel"}
+	fieldsGps       = map[uint16]string{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"}
+	fieldsInterop   = map[uint16]string{0x1: "InteroperabilityIndex"}
+	fieldsThumbnail = map[uint16]string{0x201: "ThumbJPEGInterchangeFormat", 0x202: "ThumbJPEGInterchangeFormatLength"}
+
+	fieldsAll = map[uint16]string{}
+)
+
+func init() {
+	for k, v := range fieldsExif {
+		fieldsAll[k] = v
+	}
+	for k, v := range fieldsGps {
+		fieldsAll[k] = v
+	}
+	for k, v := range fieldsInterop {
+		fieldsAll[k] = v
+	}
+	for k, v := range fieldsThumbnail {
+		fieldsAll[k] = v
+	}
+}

fieldsiptc.go

@@ -0,0 +1,49 @@
+package goexif
+
+var iptcFieldMap = map[uint8]iptcField{
+	0:   {"RecordVersion", false, "B"},
+	5:   {"ObjectName", false, "string"},
+	7:   {"EditStatus", false, "string"},
+	10:  {"Urgency", false, "B"},
+	15:  {"Category", true, "string"},
+	20:  {"SupplementalCategory", true, "string"},
+	22:  {"FixtureIdentifier", false, "string"},
+	25:  {"Keywords", true, "string"},
+	26:  {"ContentLocationCode", false, "string"},
+	27:  {"ContentLocationName", false, "string"},
+	30:  {"ReleaseDate", false, "string"},
+	35:  {"ReleaseTime", false, "string"},
+	37:  {"ExpirationDate", false, "string"},
+	38:  {"ExpirationTime", false, "string"},
+	40:  {"SpecialInstructions", false, "string"},
+	42:  {"ActionAdvised", false, "B"},
+	45:  {"ReferenceService", false, "string"},
+	47:  {"ReferenceDate", false, "string"},
+	50:  {"ReferenceNumber", false, "string"},
+	55:  {"DateCreated", false, "string"},
+	60:  {"TimeCreated", false, "string"},
+	62:  {"DigitalCreationDate", false, "string"},
+	63:  {"DigitalCreationTime", false, "string"},
+	65:  {"OriginatingProgram", false, "string"},
+	70:  {"ProgramVersion", false, "string"},
+	75:  {"ObjectCycle", false, "string"},
+	80:  {"Byline", false, "string"},
+	85:  {"BylineTitle", false, "string"},
+	90:  {"City", false, "string"},
+	92:  {"SubLocation", false, "string"},
+	95:  {"ProvinceState", false, "string"},
+	100: {"CountryCode", false, "string"},
+	101: {"CountryName", false, "string"},
+	103: {"OriginalTransmissionReference", false, "string"},
+	105: {"Headline", false, "string"},
+	110: {"Credit", false, "string"},
+	115: {"Source", false, "string"},
+	116: {"Copyright", false, "string"},
+	118: {"Contact", false, "string"},
+}
+
+type iptcField struct {
+	name       string
+	repeatable bool
+	format     string
+}

go.mod

@@ -2,10 +2,13 @@ module github.com/bep/goexif
 
 go 1.18
 
-require github.com/frankban/quicktest v1.14.5
+require (
+	github.com/frankban/quicktest v1.14.5
+	github.com/google/go-cmp v0.5.9
+	golang.org/x/text v0.12.0
+)
 
 require (
-	github.com/google/go-cmp v0.5.9 // indirect
 	github.com/kr/pretty v0.3.1 // indirect
 	github.com/kr/text v0.2.0 // indirect
 	github.com/rogpeppe/go-internal v1.10.0 // indirect

go.sum

@@ -11,3 +11,5 @@ github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsK
 github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
 github.com/rogpeppe/go-internal v1.10.0 h1:TMyTOH3F/DB16zRVcYyreMH6GnZZrwQVAoYjRBZyWFQ=
 github.com/rogpeppe/go-internal v1.10.0/go.mod h1:UQnix2H7Ngw/k4C5ijL5+65zddjncjaFoBhdsK/akog=
+golang.org/x/text v0.12.0 h1:k+n5B8goJNdU7hSvEtMUz3d1Q6D/XW4COJSJR6fN0mc=
+golang.org/x/text v0.12.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=