Adding basic smartcrop support.

Signed-off-by: Yoan Blanc <yoan@dosimple.ch>

image.go

@@ -41,6 +41,17 @@ func (i *Image) ResizeAndCrop(width, height int) ([]byte, error) {
 	return i.Process(options)
 }
 
+// SmartCrop produces a thumbnail aiming at focus on the interesting part.
+func (i *Image) SmartCrop(width, height int) ([]byte, error) {
+	options := Options{
+		Width:     width,
+		Height:    height,
+		Crop:      true,
+		SmartCrop: true,
+	}
+	return i.Process(options)
+}
+
 // Extract area from the by X/Y axis in the current image.
 func (i *Image) Extract(top, left, width, height int) ([]byte, error) {
 	options := Options{

image_test.go

@@ -455,6 +455,23 @@ func TestFluentInterface(t *testing.T) {
 	Write("fixtures/test_image_fluent_out.png", image.Image())
 }
 
+func TestImageSmartCrop(t *testing.T) {
+	if VipsMajorVersion >= 8 && VipsMinorVersion > 4 {
+		i := initImage("northern_cardinal_bird.jpg")
+		buf, err := i.SmartCrop(300, 300)
+		if err != nil {
+			t.Errorf("Cannot process the image: %#v", err)
+		}
+
+		err = assertSize(buf, 300, 300)
+		if err != nil {
+			t.Error(err)
+		}
+
+		Write("fixtures/test_smart_crop.jpg", buf)
+	}
+}
+
 func initImage(file string) *Image {
 	buf, _ := imageBuf(file)
 	return NewImage(buf)

options.go

@@ -193,6 +193,7 @@ type Options struct {
 	Compression    int
 	Zoom           int
 	Crop           bool
+	SmartCrop      bool
 	Enlarge        bool
 	Embed          bool
 	Flip           bool

resize.go

@@ -249,6 +249,9 @@ func extractOrEmbedImage(image *C.VipsImage, o Options) (*C.VipsImage, error) {
 	inHeight := int(image.Ysize)
 
 	switch {
+	case o.SmartCrop:
+		image, err = vipsSmartCrop(image, o.Width, o.Height)
+		break
 	case o.Crop:
 		width := int(math.Min(float64(inWidth), float64(o.Width)))
 		height := int(math.Min(float64(inHeight), float64(o.Height)))

vips.go

@@ -456,6 +456,22 @@ func vipsExtract(image *C.VipsImage, left, top, width, height int) (*C.VipsImage
 	return buf, nil
 }
 
+func vipsSmartCrop(image *C.VipsImage, width, height int) (*C.VipsImage, error) {
+	var buf *C.VipsImage
+	defer C.g_object_unref(C.gpointer(image))
+
+	if width > MaxSize || height > MaxSize {
+		return nil, errors.New("Maximum image size exceeded")
+	}
+
+	err := C.vips_smartcrop_bridge(image, &buf, C.int(width), C.int(height))
+	if err != 0 {
+		return nil, catchVipsError()
+	}
+
+	return buf, nil
+}
+
 func vipsShrinkJpeg(buf []byte, input *C.VipsImage, shrink int) (*C.VipsImage, error) {
 	var image *C.VipsImage
 	var ptr = unsafe.Pointer(&buf[0])

vips.h

@@ -303,9 +303,7 @@ vips_webpsave_bridge(VipsImage *in, void **buf, size_t *len, int strip, int qual
 int
 vips_tiffsave_bridge(VipsImage *in, void **buf, size_t *len) {
 #if (VIPS_MAJOR_VERSION >= 8 && VIPS_MINOR_VERSION >= 5)
-	return vips_tiffsave_buffer(in, buf, len,
-		NULL
-	);
+	return vips_tiffsave_buffer(in, buf, len, NULL);
 #else
 	return 0;
 #endif
@@ -572,3 +570,12 @@ vips_watermark_image(VipsImage *in, VipsImage *sub, VipsImage **out, WatermarkIm
     g_object_unref(base);
     return 0;
 }
+
+int
+vips_smartcrop_bridge(VipsImage *in, VipsImage **out, int width, int height) {
+#if (VIPS_MAJOR_VERSION >= 8 && VIPS_MINOR_VERSION >= 5)
+	return vips_smartcrop(in, out, width, height, NULL);
+#else
+	return 0;
+#endif
+}