dictgen: Added Description func to ImageHandler

cmd/dictgen/main.go

@@ -128,15 +128,8 @@ func main() {
 	if e != nil {
 		fmt.Fprintf(os.Stderr, "  Using encryption.\n")
 	}
-	switch v := ih.(type) {
-	case *dictgen.ImageHandlerBase64:
-		fmt.Fprintf(os.Stderr, "  Using image method: optimize and encode as base64 data URL (max_width=%d, max_height=%d, grayscale=%t, jpeg_quality=%d).\n", v.MaxSize.X, v.MaxSize.Y, !v.NoGrayscale, v.JPEGQuality)
-	case *dictgen.ImageHandlerEmbed:
-		fmt.Fprintf(os.Stderr, "  Using image method: add to dictzip as-is (warning: nickel is buggy with this as of firmware 4.19.14123).\n")
-	case *dictgen.ImageHandlerRemove:
-		fmt.Fprintf(os.Stderr, "  Using image method: remove images.\n")
-	default:
-		fmt.Fprintf(os.Stderr, "  Using image method: %#v.\n", v)
+	if ih != nil {
+		fmt.Fprintf(os.Stderr, "  Using image method: %s.\n", ih.Description())
 	}
 	if err := tdf.WriteDictzip(dw, ih, dictgen.ImageFuncFilesystem); err != nil {
 		f.Close()

dictgen/image.go

@@ -45,6 +45,9 @@ type ImageHandler interface {
 	// addition, custom CSS (which must not contain any double quotes) can be
 	// returned to be set on the img tag.
 	Transform(src string, ir io.Reader, dw *kobodict.Writer) (nsrc string, css string, err error)
+
+	// Description returns a human-readable description of what the handler does.
+	Description() string
 }
 
 // ImageHandlerRemove removes images from the dicthtml.
@@ -55,6 +58,11 @@ func (*ImageHandlerRemove) Transform(string, io.Reader, *kobodict.Writer) (strin
 	return "", "", nil
 }
 
+// Description implements ImageHandler.
+func (*ImageHandlerRemove) Description() string {
+	return "remove images"
+}
+
 // ImageHandlerEmbed adds the images to the dictzip without any additional
 // modifications. Usually, this would be the best choice, but unfortunately,
 // it is too buggy as of firmware 4.19.14123.
@@ -78,6 +86,11 @@ func (*ImageHandlerEmbed) Transform(src string, ir io.Reader, dw *kobodict.Write
 	return "dict:///" + fn, "", nil
 }
 
+// Description implements ImageHandler.
+func (*ImageHandlerEmbed) Description() string {
+	return "add to dictzip as-is (warning: nickel is buggy with this as of firmware 4.19.14123)"
+}
+
 // ImageHandlerBase64 optimizes the image and encodes it as base64. This is the
 // most compatible option, but it comes at the expense of space and speed. In
 // addition, if there are too many images, it can lead to nickel running out of
@@ -100,37 +113,42 @@ type ImageHandlerBase64 struct {
 	JPEGQuality int
 }
 
+func (ih *ImageHandlerBase64) params() (maxWidth, maxHeight int, noGrayscale bool, jpegQuality int) {
+	mw, mh := float64(ih.MaxSize.X), float64(ih.MaxSize.Y)
+	if mw < 1 {
+		mw = 1000
+	}
+	if mh < 1 {
+		mh = 1000
+	}
+	ng := ih.NoGrayscale
+	jq := ih.JPEGQuality
+	if jq == 0 {
+		jq = 60
+	}
+	return int(mw), int(mh), ng, jq
+}
+
 // Transform implements ImageHandler.
 func (ih *ImageHandlerBase64) Transform(src string, ir io.Reader, dw *kobodict.Writer) (string, string, error) {
+	mw, mh, ng, jq := ih.params()
+
+	// decode the image
 	img, err := imaging.Decode(ir)
 	if err != nil {
 		return "", "", fmt.Errorf("ImageHandlerBase64: decode image: %w", err)
 	}
 
 	// resize it
-	mw, mh := float64(ih.MaxSize.X), float64(ih.MaxSize.Y)
-	if mw < 1 {
-		mw = 1000
-	}
-	if mh < 1 {
-		mh = 1000
-	}
 	ow, oh := float64(img.Bounds().Dx()), float64(img.Bounds().Dy())
-	sf := math.Min(mw/ow, mh/oh)
-	nw, nh := ow*sf, oh*sf
-	img = imaging.Resize(img, int(nw), int(nh), imaging.Lanczos)
+	sf := math.Min(float64(mw)/ow, float64(mh)/oh)
+	img = imaging.Resize(img, int(ow*sf), int(oh*sf), imaging.Lanczos)
 
 	// make it grayscale
-	if !ih.NoGrayscale {
+	if ng {
 		img = imaging.Grayscale(img)
 	}
 
-	// set the quality
-	jq := ih.JPEGQuality
-	if jq == 0 {
-		jq = 60
-	}
-
 	// encode the image
 	buf := bytes.NewBuffer(nil)
 	bw := base64.NewEncoder(base64.StdEncoding, buf)
@@ -146,6 +164,12 @@ func (ih *ImageHandlerBase64) Transform(src string, ir io.Reader, dw *kobodict.W
 	return "data:image/jpeg;base64," + buf.String(), css, nil
 }
 
+// Description implements ImageHandler.
+func (ih *ImageHandlerBase64) Description() string {
+	mw, mh, ng, jq := ih.params()
+	return fmt.Sprintf("optimize and encode as base64 data URL (max_width=%d, max_height=%d, grayscale=%t, jpeg_quality=%d)", mw, mh, ng, jq)
+}
+
 var imgTagRe = regexp.MustCompile(`(<img)(\s+(?:[^>]*\s+)?src\s*=\s*['"]+)([^'"]+)(['"][^>]*>)`)
 
 // transformHTMLImages transforms img tags in the specified HTML, using