Addition of optional sharpening to resize.

README.md

@@ -74,6 +74,40 @@ if err != nil {
 // do some with your resized image `buf`
 ```
 
+An image can be sharpened after resizing:
+
+```go
+sharpen := vips.Sharpen{
+    Radius:     1,
+    X1:         1.1,
+    Y2:         3,
+    Y3:         6,
+    M1:         0.3,
+    M2:         0.3,
+}
+options := vips.Options{
+	Width:        800,
+	Height:       600,
+	Crop:         false,
+	Extend:       vips.EXTEND_WHITE,
+	Interpolator: vips.BILINEAR,
+	Gravity:      vips.CENTRE,
+	Quality:      95,
+	Sharpen:      &sharpen,
+}
+f, _ := os.Open("/tmp/test.jpg")
+inBuf, _ := ioutil.ReadAll(f)
+buf, err := vips.Resize(inBuf, options)
+if err != nil {
+	fmt.Fprintln(os.Stderr, err)
+	return
+}
+// do some with your resized image `buf`
+```
+
+Information on sharpening can be found in the VIPS [documentation](http://www.vips.ecs.soton.ac.uk/supported/current/doc/html/libvips/libvips-convolution.html#vips-sharpen).
+The sample values above give a pleasing on screen sharpening without too many messy artefacts at most sizes.
+
 ## Performance
 
 Test by @lovell

vips.go

@@ -37,6 +37,7 @@ const (
 	BICUBIC Interpolator = iota
 	BILINEAR
 	NOHALO
+	LBB
 )
 
 type Extend int
@@ -50,10 +51,20 @@ var interpolations = map[Interpolator]string{
 	BICUBIC:  "bicubic",
 	BILINEAR: "bilinear",
 	NOHALO:   "nohalo",
+	LBB:	  "lbb",
 }
 
 func (i Interpolator) String() string { return interpolations[i] }
 
+type Sharpen struct {
+	Radius		int
+	X1			float64
+	Y2			float64
+	Y3			float64
+	M1			float64
+	M2			float64
+}
+
 type Options struct {
 	Height       int
 	Width        int
@@ -64,6 +75,7 @@ type Options struct {
 	Interpolator Interpolator
 	Gravity      Gravity
 	Quality      int
+	Sharpen		 *Sharpen
 }
 
 func init() {
@@ -155,6 +167,7 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 	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 {
@@ -307,6 +320,15 @@ func Resize(buf []byte, o Options) ([]byte, error) {
 		debug("canvased same as affined")
 	}
 
+	if o.Sharpen != nil {
+		err := C.vips_sharpen_0(image, &tmpImage, C.int(o.Sharpen.Radius), C.double(o.Sharpen.X1), C.double(o.Sharpen.Y2), C.double(o.Sharpen.Y3), C.double(o.Sharpen.M1), C.double(o.Sharpen.M2))
+		if err != 0 {
+			return nil, resizeError()
+		}
+		C.g_object_unref(C.gpointer(image))
+		image = tmpImage
+	}
+
 	// Always convert to sRGB colour space
 	C.vips_colourspace_0(image, &tmpImage, C.VIPS_INTERPRETATION_sRGB)
 	C.g_object_unref(C.gpointer(image))

vips.h

@@ -67,3 +67,13 @@ vips_jpegsave_custom(VipsImage *in, void **buf, size_t *len, int strip, int qual
 {
     return vips_jpegsave_buffer(in, buf, len, "strip", strip, "Q", quality, "optimize_coding", TRUE, "interlace", interlace, NULL);
 }
+
+int
+vips_sharpen_0(VipsImage *in, VipsImage **out, int radius, double x1, double y2, double y3, double m1, double m2) {
+    return vips_sharpen(in, out, "radius", radius, "x1", x1, "y2", y2, "y3", y3, "m1", m1, "m2", m2, NULL);
+};
+
+int
+vips_resize_0(VipsImage *in, VipsImage **out, double scale, VipsInterpolate *interpolator) {
+    return vips_resize(in, out, scale, "interpolate", interpolator, NULL);
+};