Commit `93c1933342`

93c1933342e5172fdd36366a4a1691fa4daf94f6

parent: ec5a5f9093

Verified · cmc

cmc <hello@cleberg.net> · 2026-09-25 23:18 UTC

Parse exiftool metadata

Layout: unified · split

internal/format/exif.go added +92

@@ -0,0 +1,92 @@
	1	package format
	2
	3	import (
	4	"encoding/json"
	5	"errors"
	6	"fmt"
	7	"math"
	8	"strconv"
	9	"strings"
	10	"time"
	11	)
	12
	13	type exifRecord struct {
	14	ImageWidth int
	15	ImageHeight int
	16	Orientation int
	17	DateTimeOriginal string
	18	CreateDate string
	19	Make string
	20	Model string
	21	LensModel string
	22	FNumber float64
	23	ExposureTime float64
	24	ISO int
	25	}
	26
	27	// parseExif reads `exiftool -json -n` output for a single file.
	28	func parseExif(data []byte) (Meta, error) {
	29	var recs []exifRecord
	30	if err := json.Unmarshal(data, &recs); err != nil {
	31	return Meta{}, fmt.Errorf("exiftool output: %w", err)
	32	}
	33	if len(recs) != 1 {
	34	return Meta{}, fmt.Errorf("exiftool output: %d records, want 1", len(recs))
	35	}
	36	e := recs[0]
	37	if e.ImageWidth == 0 \|\| e.ImageHeight == 0 {
	38	return Meta{}, errors.New("exiftool output: no image dimensions")
	39	}
	40	m := Meta{Width: e.ImageWidth, Height: e.ImageHeight, Lens: e.LensModel, ISO: e.ISO}
	41	if e.Orientation >= 5 && e.Orientation <= 8 {
	42	m.Width, m.Height = m.Height, m.Width
	43	}
	44	m.Taken = exifTime(e.DateTimeOriginal)
	45	if m.Taken.IsZero() {
	46	m.Taken = exifTime(e.CreateDate)
	47	}
	48	m.Camera = camera(e.Make, e.Model)
	49	if e.FNumber > 0 {
	50	m.Aperture = "f/" + strconv.FormatFloat(e.FNumber, 'f', -1, 64)
	51	}
	52	m.Shutter = shutter(e.ExposureTime)
	53	return m, nil
	54	}
	55
	56	// exifTime parses "YYYY:MM:DD HH:MM:SS", ignoring any trailing subseconds or zone.
	57	func exifTime(s string) time.Time {
	58	if len(s) < 19 {
	59	return time.Time{}
	60	}
	61	t, err := time.Parse("2006:01:02 15:04:05", s[:19])
	62	if err != nil {
	63	return time.Time{}
	64	}
	65	return t
	66	}
	67
	68	func camera(maker, model string) string {
	69	maker, model = strings.TrimSpace(maker), strings.TrimSpace(model)
	70	if maker == "" {
	71	return model
	72	}
	73	if model == "" {
	74	return maker
	75	}
	76	brand := strings.ToLower(strings.Fields(maker)[0])
	77	if strings.Contains(strings.ToLower(model), brand) {
	78	return model
	79	}
	80	return maker + " " + model
	81	}
	82
	83	func shutter(sec float64) string {
	84	switch {
	85	case sec <= 0:
	86	return ""
	87	case sec >= 1:
	88	return strconv.FormatFloat(sec, 'f', -1, 64) + "s"
	89	default:
	90	return "1/" + strconv.Itoa(int(math.Round(1/sec)))
	91	}
	92	}

internal/format/exif_test.go added +83

@@ -0,0 +1,83 @@
	1	package format
	2
	3	import (
	4	"testing"
	5	"time"
	6	)
	7
	8	func TestParseExifFull(t *testing.T) {
	9	data := []byte(`[{
	10	"SourceFile": "a.jpg",
	11	"ImageWidth": 6240, "ImageHeight": 4160, "Orientation": 1,
	12	"DateTimeOriginal": "2025:03:14 23:10:05",
	13	"Make": "FUJIFILM", "Model": "X-T5", "LensModel": "XF23mmF2 R WR",
	14	"FNumber": 2, "ExposureTime": 0.008, "ISO": 1600
	15	}]`)
	16	m, err := parseExif(data)
	17	if err != nil {
	18	t.Fatal(err)
	19	}
	20	want := Meta{
	21	Width: 6240, Height: 4160,
	22	Taken: time.Date(2025, 3, 14, 23, 10, 5, 0, time.UTC),
	23	Camera: "FUJIFILM X-T5",
	24	Lens: "XF23mmF2 R WR",
	25	Aperture: "f/2",
	26	Shutter: "1/125",
	27	ISO: 1600,
	28	}
	29	if m != want {
	30	t.Fatalf("got %+v\nwant %+v", m, want)
	31	}
	32	}
	33
	34	func TestParseExifRotatedSwapsDimensions(t *testing.T) {
	35	for _, o := range []string{"5", "6", "7", "8"} {
	36	m, err := parseExif([]byte(`[{"ImageWidth": 300, "ImageHeight": 200, "Orientation": ` + o + `}]`))
	37	if err != nil {
	38	t.Fatal(err)
	39	}
	40	if m.Width != 200 \|\| m.Height != 300 {
	41	t.Errorf("orientation %s: got %dx%d, want 200x300", o, m.Width, m.Height)
	42	}
	43	}
	44	}
	45
	46	func TestParseExifFallbacks(t *testing.T) {
	47	m, err := parseExif([]byte(`[{
	48	"ImageWidth": 10, "ImageHeight": 10,
	49	"CreateDate": "2024:01:02 03:04:05+01:00",
	50	"Make": "Canon", "Model": "Canon EOS R6",
	51	"FNumber": 5.6, "ExposureTime": 2
	52	}]`))
	53	if err != nil {
	54	t.Fatal(err)
	55	}
	56	if want := time.Date(2024, 1, 2, 3, 4, 5, 0, time.UTC); !m.Taken.Equal(want) {
	57	t.Errorf("Taken = %v, want %v", m.Taken, want)
	58	}
	59	if m.Camera != "Canon EOS R6" {
	60	t.Errorf("Camera = %q", m.Camera)
	61	}
	62	if m.Aperture != "f/5.6" \|\| m.Shutter != "2s" {
	63	t.Errorf("Aperture %q Shutter %q", m.Aperture, m.Shutter)
	64	}
	65	}
	66
	67	func TestParseExifMinimal(t *testing.T) {
	68	m, err := parseExif([]byte(`[{"ImageWidth": 120, "ImageHeight": 80}]`))
	69	if err != nil {
	70	t.Fatal(err)
	71	}
	72	if (m != Meta{Width: 120, Height: 80}) {
	73	t.Fatalf("got %+v", m)
	74	}
	75	}
	76
	77	func TestParseExifErrors(t *testing.T) {
	78	for _, in := range []string{`not json`, `[]`, `[{}, {}]`, `[{"ImageWidth": 10}]`} {
	79	if _, err := parseExif([]byte(in)); err == nil {
	80	t.Errorf("%s: want error", in)
	81	}
	82	}
	83	}

Commit 93c1933342

Commit `93c1933342`