feat: 生成 RAW 图像的缩略图时，旋转缩略图的方向。

pkg/thumb/libraw.go

@@ -3,7 +3,11 @@ package thumb
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
+	"image"
+	"image/jpeg"
+	"image/png"
 	"io"
 	"os"
 	"os/exec"
@@ -72,14 +76,180 @@ func (f *LibRawGenerator) Generate(ctx context.Context, file io.Reader, _ string
 	outputFilePath := inputFilePath + ".thumb.jpg"
 	defer func() { _ = os.Remove(outputFilePath) }()
 
-	// use builtin function
-	ff, err := os.OpenFile(outputFilePath, os.O_RDONLY, os.ModePerm)
+	ff, err := os.Open(outputFilePath)
 	if err != nil {
 		return nil, fmt.Errorf("failed to open temp file: %w", err)
 	}
 	defer func() { _ = ff.Close() }()
 
-	return new(Builtin).Generate(ctx, ff, outputFilePath, filepath.Base(outputFilePath), options)
+	// use builtin generator
+	result, err := new(Builtin).Generate(ctx, ff, outputFilePath, filepath.Base(outputFilePath), options)
+	if err != nil {
+		return nil, fmt.Errorf("failed to generate thumbnail: %w", err)
+	}
+
+	orientation, err := getJpegOrientation(outputFilePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get jpeg orientation: %w", err)
+	}
+	if orientation == 1 {
+		return result, nil
+	}
+
+	if err = rotateImg(result.Path, orientation); err != nil {
+		return nil, fmt.Errorf("failed to rotate image: %w", err)
+	}
+	return result, nil
+}
+
+func rotateImg(filePath string, orientation int) error {
+	resultImg, err := os.OpenFile(filePath, os.O_RDWR, 0777)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = resultImg.Close() }()
+
+	imgFlag := make([]byte, 3)
+	if _, err = io.ReadFull(resultImg, imgFlag); err != nil {
+		return err
+	}
+	if _, err = resultImg.Seek(0, 0); err != nil {
+		return err
+	}
+
+	var img image.Image
+	if bytes.Equal(imgFlag, []byte{0xFF, 0xD8, 0xFF}) {
+		img, err = jpeg.Decode(resultImg)
+	} else {
+		img, err = png.Decode(resultImg)
+	}
+	if err != nil {
+		return err
+	}
+
+	switch orientation {
+	case 8:
+		img = rotate90(img)
+	case 3:
+		img = rotate90(rotate90(img))
+	case 6:
+		img = rotate90(rotate90(rotate90(img)))
+	}
+
+	if err = resultImg.Truncate(0); err != nil {
+		return err
+	}
+	if _, err = resultImg.Seek(0, 0); err != nil {
+		return err
+	}
+
+	if bytes.Equal(imgFlag, []byte{0xFF, 0xD8, 0xFF}) {
+		return jpeg.Encode(resultImg, img, nil)
+	}
+	return png.Encode(resultImg, img)
+}
+
+func getJpegOrientation(fileName string) (int, error) {
+	f, err := os.Open(fileName)
+	if err != nil {
+		return 0, err
+	}
+	defer func() { _ = f.Close() }()
+
+	header := make([]byte, 6)
+	defer func() { header = nil }()
+	if _, err = io.ReadFull(f, header); err != nil {
+		return 0, err
+	}
+
+	// jpeg format header
+	if !bytes.Equal(header[:3], []byte{0xFF, 0xD8, 0xFF}) {
+		return 0, errors.New("not a jpeg")
+	}
+
+	// not a APP1 marker
+	if header[3] != 0xE1 {
+		return 1, nil
+	}
+
+	// exif data total length
+	totalLen := int(header[4])<<8 + int(header[5]) - 2
+	buf := make([]byte, totalLen)
+	defer func() { buf = nil }()
+	if _, err = io.ReadFull(f, buf); err != nil {
+		return 0, err
+	}
+
+	// remove Exif identifier code
+	buf = buf[6:]
+
+	// byte order
+	parse16, parse32, err := initParseMethod(buf[:2])
+	if err != nil {
+		return 0, err
+	}
+
+	// version
+	_ = buf[2:4]
+
+	// first IFD offset
+	offset := parse32(buf[4:8])
+
+	// first DE offset
+	offset += 2
+	buf = buf[offset:]
+
+	const (
+		orientationTag = 0x112
+		deEntryLength  = 12
+	)
+	for len(buf) > deEntryLength {
+		tag := parse16(buf[:2])
+		if tag == orientationTag {
+			return int(parse32(buf[8:12])), nil
+		}
+		buf = buf[deEntryLength:]
+	}
+
+	return 0, errors.New("orientation not found")
+}
+
+func initParseMethod(buf []byte) (func([]byte) int16, func([]byte) int32, error) {
+	if bytes.Equal(buf, []byte{0x49, 0x49}) {
+		return littleEndian16, littleEndian32, nil
+	}
+	if bytes.Equal(buf, []byte{0x4D, 0x4D}) {
+		return bigEndian16, bigEndian32, nil
+	}
+	return nil, nil, errors.New("invalid byte order")
+}
+
+func littleEndian16(buf []byte) int16 {
+	return int16(buf[0]) | int16(buf[1])<<8
+}
+
+func bigEndian16(buf []byte) int16 {
+	return int16(buf[1]) | int16(buf[0])<<8
+}
+
+func littleEndian32(buf []byte) int32 {
+	return int32(buf[0]) | int32(buf[1])<<8 | int32(buf[2])<<16 | int32(buf[3])<<24
+}
+
+func bigEndian32(buf []byte) int32 {
+	return int32(buf[3]) | int32(buf[2])<<8 | int32(buf[1])<<16 | int32(buf[0])<<24
+}
+
+func rotate90(img image.Image) image.Image {
+	bounds := img.Bounds()
+	width, height := bounds.Dx(), bounds.Dy()
+	newImg := image.NewRGBA(image.Rect(0, 0, height, width))
+	for x := 0; x < width; x++ {
+		for y := 0; y < height; y++ {
+			newImg.Set(y, width-x-1, img.At(x, y))
+		}
+	}
+	return newImg
 }
 
 func (f *LibRawGenerator) Priority() int {