refactor(resize)

.gitignore

@@ -4,3 +4,4 @@ bin
 /*.jpg
 /*.png
 /*.webp
+/fixtures/*_out.*

README.md

@@ -15,13 +15,13 @@ bimg was heavily inspired in [sharp](https://github.com/lovell/sharp), a great n
 
 - [libvips](https://github.com/jcupitt/libvips) v7.40.0+ (7.42.0+ recommended)
 - C compatible compiler such as gcc 4.6+ or clang 3.0+
+- Go 1.3+
 
 ## Installation
 
 ```bash
 go get gopkg.in/h2non/bimg.v0
 ```
-Requires Go 1.3+
 
 ### libvips
 
@@ -37,13 +37,22 @@ The [install script](https://github.com/lovell/sharp/blob/master/preinstall.sh)
 - Resize
 - Enlarge
 - Crop
-- Zoom
 - Rotate
 - Flip/Flop
 - Extract area
 - Extract image metadata (size, format, profile, orientation...)
 - Image conversion to multiple formats
 
+## Performance
+
+libvips is probably the faster open source solution for image processing. 
+Here you can see some performance test comparisons for multiple scenarios:
+
+- [libvips speed and memory usage](http://www.vips.ecs.soton.ac.uk/index.php?title=Speed_and_Memory_Use)
+- [sharp performance tests](https://github.com/lovell/sharp#the-task) 
+
+bimg performance tests coming soon!
+
 ## API
 
 ### Example

metadata.go

@@ -48,13 +48,13 @@ func Metadata(buf []byte) (ImageMetadata, error) {
 	}
 
 	metadata := ImageMetadata{
+		Size:        size,
+		Channels:    int(image.Bands),
 		Orientation: vipsExifOrientation(image),
 		Alpha:       vipsHasAlpha(image),
 		Profile:     vipsHasProfile(image),
 		Space:       vipsSpace(image),
-		Channels:    vipsImageBands(image),
 		Type:        getImageTypeName(imageType),
-		Size:        size,
 	}
 
 	return metadata, nil

options.go

@@ -10,6 +10,14 @@ const QUALITY = 80
 
 type Gravity int
 
+const (
+	CENTRE Gravity = iota
+	NORTH
+	EAST
+	SOUTH
+	WEST
+)
+
 type Interpolator int
 
 const (

resize.go

@@ -11,14 +11,6 @@ import (
 	"math"
 )
 
-const (
-	CENTRE Gravity = iota
-	NORTH
-	EAST
-	SOUTH
-	WEST
-)
-
 func Resize(buf []byte, o Options) ([]byte, error) {
 	defer C.vips_thread_shutdown()
 
@@ -46,37 +38,8 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 	inWidth := int(image.Xsize)
 	inHeight := int(image.Ysize)
 
-	// prepare for factor
-	factor := 0.0
-
 	// image calculations
-	switch {
+	factor := imageCalculations(o, inWidth, inHeight)
-	// Fixed width and height
-	case o.Width > 0 && o.Height > 0:
-		xf := float64(inWidth) / float64(o.Width)
-		yf := float64(inHeight) / float64(o.Height)
-		if o.Crop {
-			factor = math.Min(xf, yf)
-		} else {
-			factor = math.Max(xf, yf)
-		}
-	// Fixed width, auto height
-	case o.Width > 0:
-		factor = float64(inWidth) / float64(o.Width)
-		o.Height = int(math.Floor(float64(inHeight) / factor))
-	// Fixed height, auto width
-	case o.Height > 0:
-		factor = float64(inHeight) / float64(o.Height)
-		o.Width = int(math.Floor(float64(inWidth) / factor))
-	// Identity transform
-	default:
-		factor = 1
-		o.Width = inWidth
-		o.Height = inHeight
-	}
-
-	debug("transform from %dx%d to %dx%d", inWidth, inHeight, o.Width, o.Height)
-
 	shrink := int(math.Max(math.Floor(factor), 1))
 	residual := float64(shrink) / factor
 
@@ -91,12 +54,10 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 		}
 	}
 
-	debug("factor: %v, shrink: %v, residual: %v", factor, shrink, residual)
-
 	// Try to use libjpeg shrink-on-load
 	if imageType == JPEG && shrink >= 2 {
 		// Recalculate integral shrink and double residual
-		tmpImage, factor, err := shrinkJpeg(buf, factor, shrink)
+		tmpImage, factor, err := shrinkJpegImage(buf, factor, shrink)
 		if err != nil {
 			return nil, err
 		}
@@ -108,59 +69,36 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 		}
 	}
 
-	if shrink > 1 {
+	// Calculate integral box shrink
-		debug("shrink %d", shrink)
+	windowSize := vipsWindowSize(o.Interpolator.String())
+	if factor >= 2 && windowSize > 3 {
+		// Shrink less, affine more with interpolators that use at least 4x4 pixel window, e.g. bicubic
+		shrink = int(math.Max(float64(math.Floor(factor*3.0/windowSize)), 1))
+	}
+
 	// Use vips_shrink with the integral reduction
-		image, err = vipsShrink(image, shrink)
+	if shrink > 1 {
+		image, residual, err = shrinkImage(image, o, residual, shrink)
 		if err != nil {
 			return nil, err
 		}
-
-		// Recalculate residual float based on dimensions of required vs shrunk images
-		shrunkWidth := int(image.Xsize)
-		shrunkHeight := int(image.Ysize)
-
-		residualx := float64(o.Width) / float64(shrunkWidth)
-		residualy := float64(o.Height) / float64(shrunkHeight)
-		if o.Crop {
-			residual = math.Max(residualx, residualy)
-		} else {
-			residual = math.Min(residualx, residualy)
-		}
 	}
 
 	// Use vips_affine with the remaining float part
 	if residual != 0 {
-		debug("residual %.2f", residual)
 		image, err = vipsAffine(image, residual, o.Interpolator)
 		if err != nil {
 			return nil, err
 		}
 	}
 
-	// Crop/embed
+	debug("factor: %v, shrink: %v, residual: %v", factor, shrink, residual)
-	affinedWidth := int(image.Xsize)
-	affinedHeight := int(image.Ysize)
 
-	if affinedWidth != o.Width || affinedHeight != o.Height {
+	// Extract image
-		if o.Crop {
+	image, err = extractImage(image, o)
-			left, top := calculateCrop(affinedWidth, affinedHeight, o.Width, o.Height, o.Gravity)
-			o.Width = int(math.Min(float64(inWidth), float64(o.Width)))
-			o.Height = int(math.Min(float64(inHeight), float64(o.Height)))
-			debug("crop image to %dx%d to %dx%d", left, top, o.Width, o.Height)
-			image, err = vipsExtract(image, left, top, o.Width, o.Height)
 	if err != nil {
 		return nil, err
 	}
-		} else if o.Embed {
-			left := (o.Width - affinedWidth) / 2
-			top := (o.Height - affinedHeight) / 2
-			image, err = vipsEmbed(image, left, top, o.Width, o.Height, o.Extend)
-			if err != nil {
-				return nil, err
-			}
-		}
-	}
 
 	rotation, flip := calculateRotationAndFlip(image, o.Rotate)
 	if flip {
@@ -171,8 +109,7 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 	}
 
 	if o.Rotate > 0 {
-		rotation := calculateRotation(o.Rotate)
+		image, err = vipsRotate(image, getAngle(o.Rotate))
-		image, err = vipsRotate(image, rotation)
 		if err != nil {
 			return nil, err
 		}
@@ -195,11 +132,67 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
-	C.vips_error_clear()
 
 	return buf, nil
 }
 
+func extractImage(image *C.struct__VipsImage, o Options) (*C.struct__VipsImage, error) {
+	var err error = nil
+	affinedWidth := int(image.Xsize)
+	affinedHeight := int(image.Ysize)
+
+	if affinedWidth != o.Width || affinedHeight != o.Height {
+		width := int(math.Min(float64(affinedWidth), float64(o.Width)))
+		height := int(math.Min(float64(affinedHeight), float64(o.Height)))
+
+		switch {
+		case o.Crop:
+			left, top := calculateCrop(affinedWidth, affinedHeight, o.Width, o.Height, o.Gravity)
+			image, err = vipsExtract(image, left, top, width, height)
+			break
+		case o.Embed:
+			left, top := (o.Width-affinedWidth)/2, (o.Height-affinedHeight)/2
+			image, err = vipsEmbed(image, left, top, o.Width, o.Height, o.Extend)
+			break
+		case o.Top > 0 && o.Left > 0:
+			image, err = vipsExtract(image, o.Left, o.Top, width, height)
+			break
+		}
+	}
+
+	return image, err
+}
+
+func imageCalculations(o Options, inWidth, inHeight int) float64 {
+	factor := 1.0
+
+	switch {
+	// Fixed width and height
+	case o.Width > 0 && o.Height > 0:
+		xf := float64(inWidth) / float64(o.Width)
+		yf := float64(inHeight) / float64(o.Height)
+		if o.Crop {
+			factor = math.Min(xf, yf)
+		} else {
+			factor = math.Max(xf, yf)
+		}
+	// Fixed width, auto height
+	case o.Width > 0:
+		factor = float64(inWidth) / float64(o.Width)
+		o.Height = int(math.Floor(float64(inHeight) / factor))
+	// Fixed height, auto width
+	case o.Height > 0:
+		factor = float64(inHeight) / float64(o.Height)
+		o.Width = int(math.Floor(float64(inWidth) / factor))
+	// Identity transform
+	default:
+		o.Width = inWidth
+		o.Height = inHeight
+	}
+
+	return factor
+}
+
 func calculateCrop(inWidth, inHeight, outWidth, outHeight int, gravity Gravity) (int, int) {
 	left, top := 0, 0
 
@@ -266,7 +259,27 @@ func calculateRotationAndFlip(image *C.struct__VipsImage, angle Angle) (Angle, b
 	return rotate, flip
 }
 
-func shrinkJpeg(buf []byte, factor float64, shrink int) (*C.struct__VipsImage, float64, error) {
+func shrinkImage(image *C.struct__VipsImage, o Options, residual float64, shrink int) (*C.struct__VipsImage, float64, error) {
+	// Use vips_shrink with the integral reduction
+	image, err := vipsShrink(image, shrink)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	// Recalculate residual float based on dimensions of required vs shrunk images
+	residualx := float64(o.Width) / float64(image.Xsize)
+	residualy := float64(o.Height) / float64(image.Ysize)
+
+	if o.Crop {
+		residual = math.Max(residualx, residualy)
+	} else {
+		residual = math.Min(residualx, residualy)
+	}
+
+	return image, residual, nil
+}
+
+func shrinkJpegImage(buf []byte, factor float64, shrink int) (*C.struct__VipsImage, float64, error) {
 	shrinkOnLoad := 1
 
 	switch {
@@ -293,7 +306,7 @@ func shrinkJpeg(buf []byte, factor float64, shrink int) (*C.struct__VipsImage, f
 	return nil, factor, nil
 }
 
-func calculateRotation(angle Angle) Angle {
+func getAngle(angle Angle) Angle {
 	divisor := angle % 90
 	if divisor != 0 {
 		angle = angle - divisor

resize_test.go

@@ -28,14 +28,16 @@ func TestResize(t *testing.T) {
 		t.Fatal("Image is not jpeg")
 	}
 
-	err = ioutil.WriteFile("result.jpg", newImg, 0644)
+	err = ioutil.WriteFile("fixtures/test_out.jpg", newImg, 0644)
 	if err != nil {
 		t.Fatal("Cannot save the image")
 	}
 }
 
 func TestConvert(t *testing.T) {
-	options := Options{Width: 640, Height: 480, Crop: true, Type: PNG}
+	width, height := 640, 480
+
+	options := Options{Width: width, Height: height, Crop: true, Type: PNG}
 	img, err := os.Open("fixtures/test.jpg")
 	if err != nil {
 		t.Fatal(err)
@@ -56,7 +58,47 @@ func TestConvert(t *testing.T) {
 		t.Fatal("Image is not png")
 	}
 
-	err = ioutil.WriteFile("result.png", newImg, 0644)
+	size, _ := Size(newImg)
+	if size.Height != height || size.Width != width {
+		t.Fatal("Invalid image size")
+	}
+
+	err = ioutil.WriteFile("fixtures/test_out.png", newImg, 0644)
+	if err != nil {
+		t.Fatal("Cannot save the image")
+	}
+}
+
+func TestResizePngWithTransparency(t *testing.T) {
+	width, height := 300, 240
+
+	options := Options{Width: width, Height: height, Crop: true}
+	img, err := os.Open("fixtures/transparent.png")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer img.Close()
+
+	buf, err := ioutil.ReadAll(img)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	newImg, err := Resize(buf, options)
+	if err != nil {
+		t.Errorf("Resize(imgData, %#v) error: %#v", options, err)
+	}
+
+	if DetermineImageType(newImg) != PNG {
+		t.Fatal("Image is not png")
+	}
+
+	size, _ := Size(newImg)
+	if size.Height != height || size.Width != width {
+		t.Fatal("Invalid image size")
+	}
+
+	err = ioutil.WriteFile("fixtures/transparent_out.png", newImg, 0644)
 	if err != nil {
 		t.Fatal("Cannot save the image")
 	}

vips.go

@@ -209,18 +209,14 @@ func vipsHasProfile(image *C.struct__VipsImage) bool {
 	return int(C.has_profile_embed(image)) > 0
 }
 
-func vipsWindowSize(name string) int {
+func vipsWindowSize(name string) float64 {
-	return int(C.interpolator_window_size(C.CString(name)))
+	return float64(C.interpolator_window_size(C.CString(name)))
 }
 
 func vipsSpace(image *C.struct__VipsImage) string {
 	return C.GoString(C.vips_enum_nick_bridge(image))
 }
 
-func vipsImageBands(image *C.struct__VipsImage) int {
-	return int(C.vips_image_bands(image))
-}
-
 type vipsSaveOptions struct {
 	Quality     int
 	Compression int
@@ -232,6 +228,10 @@ func vipsSave(image *C.struct__VipsImage, o vipsSaveOptions) ([]byte, error) {
 	length := C.size_t(0)
 	err := C.int(0)
 
+	// cleanup
+	defer C.g_object_unref(C.gpointer(image))
+	defer C.g_free(C.gpointer(ptr))
+
 	switch {
 	case o.Type == PNG:
 		err = C.vips_pngsave_bridge(image, &ptr, &length, 1, C.int(o.Compression), C.int(o.Quality), 0)
@@ -244,14 +244,12 @@ func vipsSave(image *C.struct__VipsImage, o vipsSaveOptions) ([]byte, error) {
 		break
 	}
 
-	C.g_object_unref(C.gpointer(image))
 	if err != 0 {
 		return nil, catchVipsError()
 	}
 
 	buf := C.GoBytes(ptr, C.int(length))
-	// cleanup
+	C.vips_error_clear()
-	C.g_free(C.gpointer(ptr))
 
 	return buf, nil
 }

vips.h

@@ -97,11 +97,6 @@ vips_enum_nick_bridge(VipsImage *image) {
 	return vips_enum_nick(VIPS_TYPE_INTERPRETATION, image->Type);
 };
 
-int
-vips_image_bands(VipsImage *image) {
-	return image->Bands;
-};
-
 int
 vips_embed_bridge(VipsImage *in, VipsImage **out, int left, int top, int width, int height, int extend)
 {