From 0e934e02cdc9eabf534aff2bb33c137a4e937d5c Mon Sep 17 00:00:00 2001
From: Ian Gulliver <github@flamingcow.io>
Date: Sun, 16 Aug 2026 16:29:03 -0700
Subject: [PATCH] Apply EXIF orientation when generating thumbnails

---
 go.mod                |  3 +-
 go.sum                |  4 +--
 internal/blob/blob.go | 68 +++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 69 insertions(+), 6 deletions(-)

diff --git a/go.mod b/go.mod
index 28854b7..a0bb72a 100644
--- a/go.mod
+++ b/go.mod
@@ -5,6 +5,8 @@ go 1.26
 require (
 	github.com/chromedp/cdproto v0.0.0-20260714215040-dc233986426f
 	github.com/chromedp/chromedp v0.16.0
+	github.com/rwcarlsen/goexif v0.0.0-20190401172101-9e8deecbddbd
+	golang.org/x/image v0.45.0
 	google.golang.org/api v0.293.0
 )
 
@@ -31,7 +33,6 @@ require (
 	go.opentelemetry.io/otel/metric v1.44.0 // indirect
 	go.opentelemetry.io/otel/trace v1.44.0 // indirect
 	golang.org/x/crypto v0.54.0 // indirect
-	golang.org/x/image v0.45.0 // indirect
 	golang.org/x/net v0.57.0 // indirect
 	golang.org/x/oauth2 v0.36.0 // indirect
 	golang.org/x/sys v0.47.0 // indirect
diff --git a/go.sum b/go.sum
index 84bd9bd..3b9e366 100644
--- a/go.sum
+++ b/go.sum
@@ -47,6 +47,8 @@ github.com/orisano/pixelmatch v0.0.0-20220722002657-fb0b55479cde h1:x0TT0RDC7UhA
 github.com/orisano/pixelmatch v0.0.0-20220722002657-fb0b55479cde/go.mod h1:nZgzbfBr3hhjoZnS66nKrHmduYNpc34ny7RK4z5/HM0=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
 github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rwcarlsen/goexif v0.0.0-20190401172101-9e8deecbddbd h1:CmH9+J6ZSsIjUK3dcGsnCnO41eRBOnY12zwkn5qVwgc=
+github.com/rwcarlsen/goexif v0.0.0-20190401172101-9e8deecbddbd/go.mod h1:hPqNNc0+uJM6H+SuU8sEs5K5IQeKccPqeSjfgcKGgPk=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
@@ -78,8 +80,6 @@ golang.org/x/sync v0.22.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
 golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
-golang.org/x/text v0.40.0 h1:Ub2Z6/xjgF1WrYQz2nuITOEegKFtiIy+rieRJ5lHZKs=
-golang.org/x/text v0.40.0/go.mod h1:hpnzDAfGV753zIKo+wk3u1bVKCGPbrnF7+7LBF/UHVY=
 golang.org/x/text v0.41.0 h1:vz/seA0lnX87Othu2f/0L24RcgrXD9/YFTSuGjj3rH8=
 golang.org/x/text v0.41.0/go.mod h1:jvf1O8ajNzZqhSrQBPbutR/EB83Cc0CFrezNQIwbb5M=
 golang.org/x/time v0.15.0 h1:bbrp8t3bGUeFOx08pvsMYRTCVSMk89u4tKbNOZbp88U=
diff --git a/internal/blob/blob.go b/internal/blob/blob.go
index 39a7b82..7be6c09 100644
--- a/internal/blob/blob.go
+++ b/internal/blob/blob.go
@@ -18,6 +18,7 @@ import (
 	_ "image/gif"
 	_ "image/png"
 
+	"github.com/rwcarlsen/goexif/exif"
 	"golang.org/x/image/draw"
 	_ "golang.org/x/image/webp"
 
@@ -320,16 +321,77 @@ func thumbnail(src []byte) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+	o := orientation(src)
 	bounds := img.Bounds()
-	if bounds.Dx() > thumbWidth {
-		height := bounds.Dy() * thumbWidth / bounds.Dx()
-		scaled := image.NewRGBA(image.Rect(0, 0, thumbWidth, height))
+	displayWidth := bounds.Dx()
+	if o >= 5 {
+		displayWidth = bounds.Dy()
+	}
+	if displayWidth > thumbWidth {
+		w := bounds.Dx() * thumbWidth / displayWidth
+		h := bounds.Dy() * thumbWidth / displayWidth
+		scaled := image.NewRGBA(image.Rect(0, 0, w, h))
 		draw.CatmullRom.Scale(scaled, scaled.Bounds(), img, bounds, draw.Over, nil)
 		img = scaled
 	}
+	img = reorient(img, o)
 	var buf bytes.Buffer
 	if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: 80}); err != nil {
 		return nil, err
 	}
 	return buf.Bytes(), nil
 }
+
+func orientation(src []byte) (o int) {
+	o = 1
+	defer func() { recover() }()
+	parsed, err := exif.Decode(bytes.NewReader(src))
+	if err != nil {
+		return
+	}
+	tag, err := parsed.Get(exif.Orientation)
+	if err != nil {
+		return
+	}
+	value, err := tag.Int(0)
+	if err != nil || value < 1 || value > 8 {
+		return
+	}
+	return value
+}
+
+func reorient(img image.Image, o int) image.Image {
+	if o == 1 {
+		return img
+	}
+	b := img.Bounds()
+	w, h := b.Dx(), b.Dy()
+	dw, dh := w, h
+	if o >= 5 {
+		dw, dh = h, w
+	}
+	out := image.NewRGBA(image.Rect(0, 0, dw, dh))
+	for y := range h {
+		for x := range w {
+			var dx, dy int
+			switch o {
+			case 2:
+				dx, dy = w-1-x, y
+			case 3:
+				dx, dy = w-1-x, h-1-y
+			case 4:
+				dx, dy = x, h-1-y
+			case 5:
+				dx, dy = y, x
+			case 6:
+				dx, dy = h-1-y, x
+			case 7:
+				dx, dy = h-1-y, w-1-x
+			case 8:
+				dx, dy = y, w-1-x
+			}
+			out.Set(dx, dy, img.At(b.Min.X+x, b.Min.Y+y))
+		}
+	}
+	return out
+}