Add WebP shrink-on-load support via scale parameter

vips/foreign.c

@@ -114,6 +114,7 @@ int set_webpload_options(VipsOperation *operation, LoadParams *params) {
   MAYBE_SET_INT(operation, params->page, "page");
   MAYBE_SET_INT(operation, params->n, "n");
   MAYBE_SET_INT(operation, params->access, "access");
+  MAYBE_SET_DOUBLE(operation, params->webpScale, "scale");
   return 0;
 }
 
@@ -527,6 +528,7 @@ LoadParams create_load_params(ImageType inputFormat) {
       .n = defaultParam,
       .dpi = defaultParam,
       .jpegShrink = defaultParam,
+      .webpScale = defaultParam,
       .heifThumbnail = defaultParam,
       .svgUnlimited = defaultParam,
       .access = defaultParam,

vips/foreign.go

@@ -365,6 +365,12 @@ func maybeSetIntParam(p IntParameter, cp *C.Param) {
 	}
 }
 
+func maybeSetDoubleParam(p Float64Parameter, cp *C.Param) {
+	if p.IsSet() {
+		C.set_double_param(cp, C.gdouble(p.Get()))
+	}
+}
+
 func createImportParams(format ImageType, params *ImportParams) C.LoadParams {
 	p := C.create_load_params(C.ImageType(format))
 
@@ -373,6 +379,7 @@ func createImportParams(format ImageType, params *ImportParams) C.LoadParams {
 	maybeSetIntParam(params.Page, &p.page)
 	maybeSetIntParam(params.NumPages, &p.n)
 	maybeSetIntParam(params.JpegShrinkFactor, &p.jpegShrink)
+	maybeSetDoubleParam(params.WebpScaleFactor, &p.webpScale)
 	maybeSetBoolParam(params.HeifThumbnail, &p.heifThumbnail)
 	maybeSetBoolParam(params.SvgUnlimited, &p.svgUnlimited)
 	maybeSetIntParam(params.Access, &p.access)

vips/foreign.h

@@ -65,6 +65,7 @@ typedef struct LoadParams {
   Param n;
   Param dpi;
   Param jpegShrink;
+  Param webpScale;
   Param heifThumbnail;
   Param svgUnlimited;
   Param access;

vips/image.go

@@ -115,6 +115,7 @@ type ImportParams struct {
 	Density     IntParameter
 
 	JpegShrinkFactor IntParameter
+	WebpScaleFactor  Float64Parameter
 	HeifThumbnail    BoolParameter
 	SvgUnlimited     BoolParameter
 	Access           IntParameter
@@ -145,6 +146,9 @@ func (i *ImportParams) OptionString() string {
 	if v := i.JpegShrinkFactor; v.IsSet() {
 		values = append(values, "shrink="+strconv.Itoa(v.Get()))
 	}
+	if v := i.WebpScaleFactor; v.IsSet() {
+		values = append(values, "scale="+strconv.FormatFloat(v.Get(), 'f', -1, 64))
+	}
 	if v := i.AutoRotate; v.IsSet() {
 		values = append(values, "autorotate="+boolToStr(v.Get()))
 	}

vips/image_test.go

@@ -1927,6 +1927,25 @@ func TestOptionString(t *testing.T) {
 	})
 }
 
+func TestWebpScaleFactor(t *testing.T) {
+	require.NoError(t, Startup(nil))
+
+	params := NewImportParams()
+	params.WebpScaleFactor.Set(0.5)
+	img, err := LoadImageFromFile(resources+"webp+alpha.webp", params)
+	require.NoError(t, err)
+	defer img.Close()
+
+	assert.Equal(t, 400, img.Width())
+	assert.Equal(t, 300, img.Height())
+}
+
+func TestOptionString_WebpScale(t *testing.T) {
+	p := &ImportParams{}
+	p.WebpScaleFactor.Set(0.25)
+	assert.Contains(t, p.OptionString(), "scale=0.25")
+}
+
 func TestExportNative_MoreFormats(t *testing.T) {
 	require.NoError(t, Startup(nil))