Add webp image encoding support

Fixes #5924

resources/images/image.go

@@ -23,6 +23,9 @@ import (
 	"io"
 	"sync"
 
+	"github.com/bep/gowebp/libwebp/webpoptions"
+	"github.com/gohugoio/hugo/resources/images/webp"
+
 	"github.com/gohugoio/hugo/media"
 	"github.com/gohugoio/hugo/resources/images/exif"
 
@@ -89,6 +92,15 @@ func (i *Image) EncodeTo(conf ImageConfig, img image.Image, w io.Writer) error {
 
 	case BMP:
 		return bmp.Encode(w, img)
+	case WEBP:
+		return webp.Encode(
+			w,
+			img, webpoptions.EncodingOptions{
+				Quality:        conf.Quality,
+				EncodingPreset: webpoptions.EncodingPreset(conf.Hint),
+				UseSharpYuv:    true,
+			},
+		)
 	default:
 		return errors.New("format not supported")
 	}
@@ -229,10 +241,11 @@ func (p *ImageProcessor) Filter(src image.Image, filters ...gift.Filter) (image.
 	return dst, nil
 }
 
-func (p *ImageProcessor) GetDefaultImageConfig(action string) ImageConfig {
+func GetDefaultImageConfig(action string, defaults ImagingConfig) ImageConfig {
 	return ImageConfig{
 		Action:  action,
-		Quality: p.Cfg.Cfg.Quality,
+		Hint:    defaults.Hint,
+		Quality: defaults.Cfg.Quality,
 	}
 }
 
@@ -250,11 +263,13 @@ const (
 	GIF
 	TIFF
 	BMP
+	WEBP
 )
 
-// RequiresDefaultQuality returns if the default quality needs to be applied to images of this format
+// RequiresDefaultQuality returns if the default quality needs to be applied to
+// images of this format.
 func (f Format) RequiresDefaultQuality() bool {
-	return f == JPEG
+	return f == JPEG || f == WEBP
 }
 
 // SupportsTransparency reports whether it supports transparency in any form.
@@ -281,6 +296,8 @@ func (f Format) MediaType() media.Type {
 		return media.TIFFType
 	case BMP:
 		return media.BMPType
+	case WEBP:
+		return media.WEBPType
 	default:
 		panic(fmt.Sprintf("%d is not a valid image format", f))
 	}