fix(#46): infer resize operation

resize.go

@@ -23,17 +23,6 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 		return nil, err
 	}
 
-	// Defaults
-	if o.Quality == 0 {
-		o.Quality = QUALITY
-	}
-	if o.Compression == 0 {
-		o.Compression = 6
-	}
-	if o.Type == 0 {
-		o.Type = imageType
-	}
-
 	if IsTypeSupported(o.Type) == false {
 		return nil, errors.New("Unsupported image output type")
 	}
@@ -43,14 +32,20 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 	inWidth := int(image.Xsize)
 	inHeight := int(image.Ysize)
 
+	// Define default options
+	applyDefaults(&o, imageType)
+	// Infer the required operation based on the in/out image sizes for a coherent transformation
+	normalizeOperation(&o, inWidth, inHeight)
+
 	// image calculations
 	factor := imageCalculations(&o, inWidth, inHeight)
 	shrink := calculateShrink(factor, o.Interpolator)
 	residual := calculateResidual(factor, shrink)
 
-	// Do not enlarge the output if the input width *or* height are already less than the required dimensions
+	// Do not enlarge the output if the input width or height
+	// are already less than the required dimensions
 	if o.Enlarge == false {
-		if inWidth < o.Width && inHeight < o.Height {
+		if inWidth < o.Width || inHeight < o.Height {
 			factor = 1.0
 			shrink = 1
 			residual = 0
@@ -88,7 +83,6 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 	transformImage := o.Width != inWidth || o.Height != inHeight || o.AreaWidth > 0 || o.AreaHeight > 0
 
 	if transformImage {
-
 		// Use vips_shrink with the integral reduction
 		if shrink > 1 {
 			image, residual, err = shrinkImage(image, o, residual, shrink)
@@ -138,6 +132,28 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 	return buf, nil
 }
 
+func applyDefaults(o *Options, imageType ImageType) {
+	if o.Quality == 0 {
+		o.Quality = QUALITY
+	}
+	if o.Compression == 0 {
+		o.Compression = 6
+	}
+	if o.Type == 0 {
+		o.Type = imageType
+	}
+}
+
+func normalizeOperation(o *Options, inWidth, inHeight int) {
+	if o.Crop == false && o.Enlarge == false && o.Rotate == 0 && (o.Width > 0 || o.Height > 0) {
+		if inWidth > o.Width || inHeight > o.Height {
+			o.Crop = true
+		} else {
+			o.Enlarge = true
+		}
+	}
+}
+
 func extractImage(image *C.struct__VipsImage, o Options) (*C.struct__VipsImage, error) {
 	var err error = nil
 	inWidth := int(image.Xsize)
@@ -239,7 +255,6 @@ func zoomImage(image *C.struct__VipsImage, zoom int) (*C.struct__VipsImage, erro
 	if zoom == 0 {
 		return image, nil
 	}
-
 	return vipsZoom(image, zoom+1)
 }
 
@@ -250,13 +265,12 @@ func affineImage(image *C.struct__VipsImage, o Options, residual float64) (*C.st
 		return nil, err
 	}
 
-	if o.Enlarge || (o.Width > int(newImage.Xsize) && o.Height > int(newImage.Ysize)) {
+	if o.Enlarge || o.Width > 0 || (o.Width > int(newImage.Xsize) && o.Height > int(newImage.Ysize)) {
 		C.g_object_unref(C.gpointer(image))
-		image = newImage
-	} else {
-		C.g_object_unref(C.gpointer(newImage))
+		return newImage, nil
 	}
 
+	C.g_object_unref(C.gpointer(newImage))
 	return image, nil
 }
 

resize_test.go

@@ -20,6 +20,11 @@ func TestResize(t *testing.T) {
 		t.Fatal("Image is not jpeg")
 	}
 
+	size, _ := Size(newImg)
+	if size.Height != options.Height || size.Width != options.Width {
+		t.Fatalf("Invalid image size: %dx%d", size.Width, size.Height)
+	}
+
 	Write("fixtures/test_out.jpg", newImg)
 }
 
@@ -36,12 +41,17 @@ func TestRotate(t *testing.T) {
 		t.Fatal("Image is not jpeg")
 	}
 
+	size, _ := Size(newImg)
+	if size.Height != options.Width {
+		t.Fatalf("Invalid image size: %dx%d", size.Width, size.Height)
+	}
+
 	Write("fixtures/test_rotate_out.jpg", newImg)
 }
 
-func TestCorruptedImage(t *testing.T) {
-	options := Options{Width: 800, Height: 600}
-	buf, _ := Read("fixtures/corrupt.jpg")
+func TestInvalidRotate(t *testing.T) {
+	options := Options{Width: 800, Height: 600, Rotate: 111}
+	buf, _ := Read("fixtures/test.jpg")
 
 	newImg, err := Resize(buf, options)
 	if err != nil {
@@ -52,12 +62,17 @@ func TestCorruptedImage(t *testing.T) {
 		t.Fatal("Image is not jpeg")
 	}
 
-	Write("fixtures/test_corrupt_out.jpg", newImg)
+	size, _ := Size(newImg)
+	if size.Height != options.Width {
+		t.Fatalf("Invalid image size: %dx%d", size.Width, size.Height)
 	}
 
-func TestInvalidRotate(t *testing.T) {
-	options := Options{Width: 800, Height: 600, Rotate: 111}
-	buf, _ := Read("fixtures/test.jpg")
+	Write("fixtures/test_invalid_rotate_out.jpg", newImg)
+}
+
+func TestCorruptedImage(t *testing.T) {
+	options := Options{Width: 800, Height: 600}
+	buf, _ := Read("fixtures/corrupt.jpg")
 
 	newImg, err := Resize(buf, options)
 	if err != nil {
@@ -68,7 +83,12 @@ func TestInvalidRotate(t *testing.T) {
 		t.Fatal("Image is not jpeg")
 	}
 
-	Write("fixtures/test_invalid_rotate_out.jpg", newImg)
+	size, _ := Size(newImg)
+	if size.Height != options.Height || size.Width != options.Width {
+		t.Fatalf("Invalid image size: %dx%d", size.Width, size.Height)
+	}
+
+	Write("fixtures/test_corrupt_out.jpg", newImg)
 }
 
 func TestNoColorProfile(t *testing.T) {
@@ -84,6 +104,11 @@ func TestNoColorProfile(t *testing.T) {
 	if metadata.Profile == true {
 		t.Fatal("Invalid profile data")
 	}
+
+	size, _ := Size(newImg)
+	if size.Height != options.Height || size.Width != options.Width {
+		t.Fatalf("Invalid image size: %dx%d", size.Width, size.Height)
+	}
 }
 
 func TestConvert(t *testing.T) {

vips.go

@@ -78,11 +78,12 @@ func Initialize() {
 	C.vips_cache_set_max_mem(maxCacheMem)
 	C.vips_cache_set_max(maxCacheSize)
 
-	// Define a custom libvips thread concurrency limit (this may generate thread-unsafe issues)
+	// Define a custom thread concurrency limit in libvips (this may generate thread-unsafe issues)
 	// See: https://github.com/jcupitt/libvips/issues/261#issuecomment-92850414
 	if os.Getenv("VIPS_CONCURRENCY") == "" {
 		C.vips_concurrency_set(1)
 	}
+
 	// Enable libvips cache tracing
 	if os.Getenv("VIPS_TRACE") != "" {
 		C.vips_enable_cache_set_trace()
@@ -91,7 +92,8 @@ func Initialize() {
 	initialized = true
 }
 
-// Thread-safe function to shutdown libvips. You could call this to drop caches as well.
+// Thread-safe function to shutdown libvips.
+// You can call this to drop caches as well.
 // If libvips was already initialized, the function is no-op
 func Shutdown() {
 	m.Lock()