add jpeg encoder

image.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"image"
 	"image/color"
+	"image/jpeg"
 	"image/png"
 	"io"
 )
@@ -15,8 +16,19 @@ func createBarnsleyFernPng(s *settings, w io.Writer) error {
 
 	drawBarnsleyFern(img, newColorFunc(s.CM), s.Dots)
 
-	if err := png.Encode(w, img); err != nil {
-		return errors.Join(errEncodePng, err)
+	switch s.OM {
+	case outputjpeg:
+		opts := &jpeg.Options{
+			Quality: 100,
+		}
+		if err := jpeg.Encode(w, img, opts); err != nil {
+			return errors.Join(errEncodePng, err)
+		}
+
+	case outputpng:
+		if err := png.Encode(w, img); err != nil {
+			return errors.Join(errEncodePng, err)
+		}
 	}
 
 	return nil