gaussian blur support min_ampl (davidbyttow#307)

Co-authored-by: muyouran <[email protected]>

vips/convolution.c

@@ -1,7 +1,7 @@
 #include "convolution.h"
 
-int gaussian_blur_image(VipsImage *in, VipsImage **out, double sigma) {
-  return vips_gaussblur(in, out, sigma, NULL);
+int gaussian_blur_image(VipsImage *in, VipsImage **out, double sigma, double min_ampl) {
+    return vips_gaussblur(in, out, sigma, "min_ampl", min_ampl, NULL);
 }
 
 int sharpen_image(VipsImage *in, VipsImage **out, double sigma, double x1,

vips/convolution.go

@@ -4,11 +4,11 @@ package vips
 import "C"
 
 // https://libvips.github.io/libvips/API/current/libvips-convolution.html#vips-gaussblur
-func vipsGaussianBlur(in *C.VipsImage, sigma float64) (*C.VipsImage, error) {
+func vipsGaussianBlur(in *C.VipsImage, sigma, minAmpl float64) (*C.VipsImage, error) {
 	incOpCounter("gaussblur")
 	var out *C.VipsImage
 
-	if err := C.gaussian_blur_image(in, &out, C.double(sigma)); err != 0 {
+	if err := C.gaussian_blur_image(in, &out, C.double(sigma), C.double(minAmpl)); err != 0 {
 		return nil, handleImageError(out)
 	}
 

vips/convolution.h

@@ -3,6 +3,6 @@
 #include <stdlib.h>
 #include <vips/vips.h>
 
-int gaussian_blur_image(VipsImage *in, VipsImage **out, double sigma);
+int gaussian_blur_image(VipsImage *in, VipsImage **out, double sigma, double min_ampl);
 int sharpen_image(VipsImage *in, VipsImage **out, double sigma, double x1,
                   double m2);

vips/image.go

@@ -17,6 +17,8 @@ import (
 	"unsafe"
 )
 
+const GaussBlurDefaultMinAMpl = 0.2
+
 // PreMultiplicationState stores the pre-multiplication band format of the image
 type PreMultiplicationState struct {
 	bandFormat BandFormat
@@ -1364,8 +1366,16 @@ func (r *ImageRef) Flatten(backgroundColor *Color) error {
 }
 
 // GaussianBlur blurs the image
-func (r *ImageRef) GaussianBlur(sigma float64) error {
-	out, err := vipsGaussianBlur(r.image, sigma)
+// add support minAmpl
+func (r *ImageRef) GaussianBlur(sigmas ...float64) error {
+	var (
+		sigma  = sigmas[0]
+		minAmpl  = GaussBlurDefaultMinAMpl
+	)
+	if len(sigmas) >= 2 {
+		minAmpl = sigmas[1]
+	}
+	out, err := vipsGaussianBlur(r.image, sigma, minAmpl)
 	if err != nil {
 		return err
 	}

vips/image_golden_test.go

@@ -490,6 +490,9 @@ func TestImage_GaussianBlur(t *testing.T) {
 	goldenTest(t, resources+"jpg-24bit.jpg", func(img *ImageRef) error {
 		return img.GaussianBlur(10.5)
 	}, nil, nil)
+	goldenTest(t, resources+"jpg-24bit.jpg", func(img *ImageRef) error {
+		return img.GaussianBlur(10.5,0.2)
+	}, nil, nil)
 }
 
 func TestImage_BandJoinConst(t *testing.T) {