Add the option to use background and threshold options on trim

image_test.go

@@ -495,6 +495,31 @@ func TestImageTrim(t *testing.T) {
 	Write("testdata/transparent_trim.png", buf)
 }
 
+func TestImageTrimParameters(t *testing.T) {
+
+	if !(VipsMajorVersion >= 8 && VipsMinorVersion >= 6) {
+		t.Skipf("Skipping this test, libvips doesn't meet version requirement %s >= 8.6", VipsVersion)
+	}
+
+	i := initImage("test.png")
+	options := Options{
+		Trim:       true,
+		Background: Color{0.0, 0.0, 0.0},
+		Threshold:  10.0,
+	}
+	buf, err := i.Process(options)
+	if err != nil {
+		t.Errorf("Cannot process the image: %#v", err)
+	}
+
+	err = assertSize(buf, 400, 257)
+	if err != nil {
+		t.Errorf("The image wasn't trimmed.")
+	}
+
+	Write("testdata/transparent_trim.png", buf)
+}
+
 func TestImageLength(t *testing.T) {
 	i := initImage("test.jpg")
 

options.go

@@ -217,5 +217,6 @@ type Options struct {
 	Interpretation Interpretation
 	GaussianBlur   GaussianBlur
 	Sharpen        Sharpen
+	Threshold      float32
 	OutputICC      string
 }

resizer.go

@@ -273,7 +273,7 @@ func extractOrEmbedImage(image *C.VipsImage, o Options) (*C.VipsImage, error) {
 		image, err = vipsEmbed(image, left, top, o.Width, o.Height, o.Extend, o.Background)
 		break
 	case o.Trim:
-		left, top, width, height, err := vipsTrim(image)
+		left, top, width, height, err := vipsTrim(image, o.Background, o.Threshold)
 		if err == nil {
 			image, err = vipsExtract(image, left, top, width, height)
 		}

vips.go

@@ -503,7 +503,7 @@ func vipsSmartCrop(image *C.VipsImage, width, height int) (*C.VipsImage, error)
 	return buf, nil
 }
 
-func vipsTrim(image *C.VipsImage) (int, int, int, int, error) {
+func vipsTrim(image *C.VipsImage, background Color, threshold float32) (int, int, int, int, error) {
 	defer C.g_object_unref(C.gpointer(image))
 
 	top := C.int(0)
@@ -511,7 +511,10 @@ func vipsTrim(image *C.VipsImage) (int, int, int, int, error) {
 	width := C.int(0)
 	height := C.int(0)
 
-	err := C.vips_find_trim_bridge(image, &top, &left, &width, &height)
+	err := C.vips_find_trim_bridge(image,
+		&top, &left, &width, &height,
+		C.double(background.R), C.double(background.G), C.double(background.B),
+		C.double(threshold))
 	if err != 0 {
 		return 0, 0, 0, 0, catchVipsError()
 	}

vips.h

@@ -545,9 +545,17 @@ vips_smartcrop_bridge(VipsImage *in, VipsImage **out, int width, int height) {
 #endif
 }
 
-int vips_find_trim_bridge(VipsImage *in, int *top, int *left, int *width, int *height) {
+int vips_find_trim_bridge(VipsImage *in, int *top, int *left, int *width, int *height, double r, double g, double b, double threshold) {
 #if (VIPS_MAJOR_VERSION >= 8 && VIPS_MINOR_VERSION >= 6)
-	return vips_find_trim(in, top, left, width, height, NULL);
+	if (vips_is_16bit(in->Type)) {
+		r = 65535 * r / 255;
+		g = 65535 * g / 255;
+		b = 65535 * b / 255;
+	}
+
+	double background[3] = {r, g, b};
+	VipsArrayDouble *vipsBackground = vips_array_double_new(background, 3);
+	return vips_find_trim(in, top, left, width, height, "background", vipsBackground, "threshold", threshold, NULL);
 #else
 	return 0;
 #endif