resizing image on thread instead of ui thread

main.go

@@ -29,16 +29,17 @@ type incomingImage struct {
 }
 
 type Animation struct {
-	ctx       *gg.Context
-	position  image.Point
-	dir       image.Point
-	height    int
-	width     int
-	stroke    int
-	image     []image.Image
-	updown    int
-	mqmsg     chan mqtt.Message
-	msg       string
+	ctx      *gg.Context
+	position image.Point
+	dir      image.Point
+	height   int
+	width    int
+	stroke   int
+	image    []image.Image
+	updown   int
+	mqmsg    chan mqtt.Message
+	msg      string
+
 	countDown int
 }
 
@@ -140,6 +141,12 @@ func NewAnimation(sz image.Point, mqMessages chan mqtt.Message) *Animation {
 	}
 }
 
+func appendImage(img string, a *Animation) {
+	baseImage, _ := b64.StdEncoding.DecodeString(img)
+	bigImage, _, _ := image.Decode(bytes.NewReader(baseImage))
+	a.image = append(a.image, imaging.Resize(bigImage, 32, 32, imaging.Lanczos))
+}
+
 // what happens each frame, at an interval of 50 milliseconds
 func (a *Animation) Next() (image.Image, <-chan time.Time, error) {
 	incoming := incomingImage{}
@@ -168,10 +175,7 @@ func (a *Animation) Next() (image.Image, <-chan time.Time, error) {
 			a.msg = string(msg.Payload())
 			a.ctx.DrawString(a.msg, 5, 9)
 		} else {
-			baseImage, _ := b64.StdEncoding.DecodeString(incoming.Image)
-			bigImage, _, _ := image.Decode(bytes.NewReader(baseImage))
-			a.image = append(a.image, imaging.Resize(bigImage, 32, 32, imaging.Lanczos))
-			a.ctx.DrawImageAnchored(a.image[2], 0, 0, 0, 0)
+			go appendImage(incoming.Image, a)
 		}
 	default:
 	}