feat: autorotate

image.go

@@ -154,6 +154,11 @@ func (i *Image) Rotate(a Angle) ([]byte, error) {
 	return i.Process(options)
 }
 
+// AutoRotate automatically rotates the image with no additional transformation based on the EXIF oritentation metadata, if available.
+func (i *Image) AutoRotate() ([]byte, error) {
+	return i.Process(Options{autoRotateOnly: true})
+}
+
 // Flip flips the image about the vertical Y axis.
 func (i *Image) Flip() ([]byte, error) {
 	options := Options{Flip: true}

image_test.go

@@ -345,6 +345,38 @@ func TestImageRotate(t *testing.T) {
 	Write("testdata/test_image_rotate_out.jpg", buf)
 }
 
+func TestImageAutoRotate(t *testing.T) {
+	tests := []struct {
+		file         string
+		orientation  int
+	}{
+		{"exif/Landscape_1.jpg", 1},
+		{"exif/Landscape_2.jpg", 2},
+		{"exif/Landscape_3.jpg", 1},
+		{"exif/Landscape_4.jpg", 4},
+		{"exif/Landscape_5.jpg", 5},
+		{"exif/Landscape_6.jpg", 1},
+		{"exif/Landscape_7.jpg", 7},
+	}
+
+	for index, test := range tests {
+		img := initImage(test.file)
+		buf, err := img.AutoRotate()
+		if err != nil {
+			t.Errorf("Cannot process the image: %#v", err)
+		}
+		Write(fmt.Sprintf("testdata/test_autorotate_%d_out.jpg", index), buf)
+
+		meta, err := img.Metadata()
+		if err != nil {
+			t.Errorf("Cannot read image metadata: %#v", err)
+		}
+		if meta.Orientation != test.orientation {
+			t.Errorf("Invalid image orientation for %s: %d != %d", test.file, meta.Orientation, test.orientation)
+		}
+	}
+}
+
 func TestImageConvert(t *testing.T) {
 	buf, err := initImage("test.jpg").Convert(PNG)
 	if err != nil {

metadata.go

@@ -25,6 +25,7 @@ type ImageMetadata struct {
 	EXIF EXIF
 }
 
+// EXIF image metadata
 type EXIF struct {
 	Make string
 	Model string

options.go

@@ -8,7 +8,7 @@ import "C"
 
 const (
 	// Quality defines the default JPEG quality to be used.
-	Quality = 80
+	Quality = 75
 	// MaxSize defines the maximum pixels width or height supported.
 	MaxSize = 16383
 )
@@ -226,4 +226,7 @@ type Options struct {
 	OutputICC      string
 	InputICC       string
 	Palette        bool
+
+	// private fields
+	autoRotateOnly bool
 }

resizer.go

@@ -30,10 +30,20 @@ func resizer(buf []byte, o Options) ([]byte, error) {
 	// Clone and define default options
 	o = applyDefaults(o, imageType)
 
+	// Ensure supported type
 	if !IsTypeSupported(o.Type) {
 		return nil, errors.New("Unsupported image output type")
 	}
 
+	// Autorate only
+	if o.autoRotateOnly {
+		image, err = vipsAutoRotate(image)
+		if err != nil {
+			return nil, err
+		}
+		return saveImage(image, o)
+	}
+
 	// Auto rotate image based on EXIF orientation header
 	image, rotated, err := rotateAndFlipImage(image, o)
 	if err != nil {
@@ -375,7 +385,6 @@ func watermarkImageWithText(image *C.VipsImage, w Watermark) (*C.VipsImage, erro
 }
 
 func watermarkImageWithAnotherImage(image *C.VipsImage, w WatermarkImage) (*C.VipsImage, error) {
-
 	if len(w.Buf) == 0 {
 		return image, nil
 	}

vips.go

@@ -272,6 +272,18 @@ func vipsRotate(image *C.VipsImage, angle Angle) (*C.VipsImage, error) {
 	return out, nil
 }
 
+func vipsAutoRotate(image *C.VipsImage) (*C.VipsImage, error) {
+	var out *C.VipsImage
+	defer C.g_object_unref(C.gpointer(image))
+
+	err := C.vips_autorot_bridge(image, &out)
+	if err != 0 {
+		return nil, catchVipsError()
+	}
+
+	return out, nil
+}
+
 func vipsTransformICC(image *C.VipsImage, inputICC string, outputICC string) (*C.VipsImage, error) {
 	var out *C.VipsImage
 	defer C.g_object_unref(C.gpointer(image))

vips.h

@@ -222,6 +222,11 @@ vips_rotate_bridge(VipsImage *in, VipsImage **out, int angle) {
 	}
 }
 
+int
+vips_autorot_bridge(VipsImage *in, VipsImage **out) {
+	return vips_autorot(in, out, NULL);
+}
+
 const char *
 vips_exif_tag(VipsImage *image, const char *tag) {
 	const char *exif;

vips_test.go

@@ -82,6 +82,42 @@ func TestVipsRotate(t *testing.T) {
 	}
 }
 
+func TestVipsAutoRotate(t *testing.T) {
+	files := []struct {
+		name         string
+		orientation  int
+	}{
+		{"test.jpg", 0},
+		{"test_exif.jpg", 0},
+		{"exif/Landscape_1.jpg", 0},
+		{"exif/Landscape_2.jpg", 2},
+		{"exif/Landscape_3.jpg", 0},
+		{"exif/Landscape_4.jpg", 4},
+		{"exif/Landscape_5.jpg", 5},
+		{"exif/Landscape_6.jpg", 0},
+		{"exif/Landscape_7.jpg", 7},
+	}
+
+	for _, file := range files {
+		image, _, _ := vipsRead(readImage(file.name))
+
+		newImg, err := vipsAutoRotate(image)
+		if err != nil {
+			t.Fatal("Cannot auto rotate the image")
+		}
+
+		orientation := vipsExifOrientation(newImg)
+		if orientation != file.orientation {
+			t.Fatalf("Invalid image orientation: %d != %d", orientation, file.orientation)
+		}
+
+		buf, _ := vipsSave(newImg, vipsSaveOptions{Quality: 95})
+		if len(buf) == 0 {
+			t.Fatal("Empty image")
+		}
+	}
+}
+
 func TestVipsZoom(t *testing.T) {
 	image, _, _ := vipsRead(readImage("test.jpg"))