Serve GIFs as well as WebP

Saw tidbyt#1005 and thought it was a fun little challenge.

Tested that this worked locally for:
 - Previewing with WebP (default)
 - Previewing with GIF (passing --gif flag)
 - Updating config using either format
 - Exporting image using either format

Inspected the images shown and confirmed that it does generate a WebP or GIF file as appropriate, and that the src element is set to the appropriate image type.

cmd/serve.go

@@ -10,6 +10,7 @@ var (
 	host  string
 	port  int
 	watch bool
+	serveGif bool
 )
 
 func init() {
@@ -18,6 +19,7 @@ func init() {
 	ServeCmd.Flags().BoolVarP(&watch, "watch", "w", true, "Reload scripts on change. Does not recurse sub-directories.")
 	ServeCmd.Flags().IntVarP(&maxDuration, "max_duration", "d", 15000, "Maximum allowed animation duration (ms)")
 	ServeCmd.Flags().IntVarP(&timeout, "timeout", "", 30000, "Timeout for execution (ms)")
+	ServeCmd.Flags().BoolVarP(&serveGif, "gif", "", false, "Generate GIF instead of WebP")
 }
 
 var ServeCmd = &cobra.Command{
@@ -33,7 +35,7 @@ containing multiple Starlark files and resources.`,
 }
 
 func serve(cmd *cobra.Command, args []string) error {
-	s, err := server.NewServer(host, port, watch, args[0], maxDuration, timeout)
+	s, err := server.NewServer(host, port, watch, args[0], maxDuration, timeout, serveGif)
 	if err != nil {
 		return err
 	}

server/browser/browser.go

@@ -1,4 +1,4 @@
-// Package browser provides the ability to send WebP images to a browser over
+// Package browser provides the ability to send images to a browser over
 // websockets.
 package browser
 
@@ -19,17 +19,18 @@ import (
 	"tidbyt.dev/pixlet/server/loader"
 )
 
-// Browser provides a structure for serving WebP images over websockets to
+// Browser provides a structure for serving WebP or GIF images over websockets to
 // a web browser.
 type Browser struct {
 	addr       string             // The address to listen on.
 	title      string             // The title of the HTML document.
-	updateChan chan loader.Update // A channel of base64 encoded WebP images.
+	updateChan chan loader.Update // A channel of base64 encoded images.
 	watch      bool
 	fo         *fanout.Fanout
 	r          *mux.Router
 	tmpl       *template.Template
 	loader     *loader.Loader
+	serveGif   bool               // True if serving GIF, false if serving WebP
 }
 
 //go:embed preview-mask.png
@@ -43,18 +44,19 @@ var previewHTML string
 
 // previewData is used to populate the HTML template.
 type previewData struct {
-	Title string `json:"title"`
-	WebP  string `json:"webp"`
-	Watch bool   `json:"-"`
-	Err   string `json:"error,omitempty"`
+	Title  string    `json:"title"`
+	Image  string    `json:"img"`
+	ImageType string `json:"img_type"`
+	Watch  bool      `json:"-"`
+	Err    string    `json:"error,omitempty"`
 }
 type handlerRequest struct {
 	ID    string `json:"id"`
 	Param string `json:"param"`
 }
 
 // NewBrowser sets up a browser structure. Call Run() to kick off the main loops.
-func NewBrowser(addr string, title string, watch bool, updateChan chan loader.Update, l *loader.Loader) (*Browser, error) {
+func NewBrowser(addr string, title string, watch bool, updateChan chan loader.Update, l *loader.Loader, serveGif bool) (*Browser, error) {
 	tmpl, err := template.New("preview").Parse(previewHTML)
 	if err != nil {
 		return nil, err
@@ -68,6 +70,7 @@ func NewBrowser(addr string, title string, watch bool, updateChan chan loader.Up
 		title:      title,
 		loader:     l,
 		watch:      watch,
+		serveGif:   serveGif,
 	}
 
 	r := mux.NewRouter()
@@ -92,6 +95,7 @@ func NewBrowser(addr string, title string, watch bool, updateChan chan loader.Up
 	// API endpoints to support the React frontend.
 	r.HandleFunc("/api/v1/preview", b.previewHandler)
 	r.HandleFunc("/api/v1/preview.webp", b.imageHandler)
+	r.HandleFunc("/api/v1/preview.gif", b.imageHandler)
 	r.HandleFunc("/api/v1/push", b.pushHandler)
 	r.HandleFunc("/api/v1/schema", b.schemaHandler).Methods("GET")
 	r.HandleFunc("/api/v1/handlers/{handler}", b.schemaHandlerHandler).Methods("POST")
@@ -103,7 +107,7 @@ func NewBrowser(addr string, title string, watch bool, updateChan chan loader.Up
 
 // Run starts the server process and runs forever in a blocking fashion. The
 // main routines include an update watcher to process incomming changes to the
-// webp and running the http handlers.
+// image and running the http handlers.
 func (b *Browser) Run() error {
 	defer b.fo.Quit()
 
@@ -170,17 +174,21 @@ func (b *Browser) imageHandler(w http.ResponseWriter, r *http.Request) {
 		config[k] = val[0]
 	}
 
-	webp, err := b.loader.LoadApplet(config)
+	img, err := b.loader.LoadApplet(config)
 	if err != nil {
 		http.Error(w, "loading applet", http.StatusInternalServerError)
 		return
 	}
 
-	w.Header().Set("Content-Type", "image/webp")
+	img_type := "image/webp"
+	if b.serveGif {
+		img_type = "image/gif"
+	}
+	w.Header().Set("Content-Type", img_type)
 
-	data, err := base64.StdEncoding.DecodeString(webp)
+	data, err := base64.StdEncoding.DecodeString(img)
 	if err != nil {
-		http.Error(w, "decoding webp", http.StatusInternalServerError)
+		http.Error(w, "decoding image", http.StatusInternalServerError)
 		return
 	}
 
@@ -199,10 +207,15 @@ func (b *Browser) previewHandler(w http.ResponseWriter, r *http.Request) {
 		config[k] = val[0]
 	}
 
-	webp, err := b.loader.LoadApplet(config)
+	img, err := b.loader.LoadApplet(config)
+	img_type := "webp"
+	if b.serveGif {
+		img_type = "gif"
+	}
 	data := &previewData{
-		WebP:  webp,
-		Title: b.title,
+		Image:     img,
+		ImageType: img_type,
+		Title:     b.title,
 	}
 	if err != nil {
 		data.Err = err.Error()
@@ -238,13 +251,19 @@ func (b *Browser) websocketHandler(w http.ResponseWriter, r *http.Request) {
 }
 
 func (b *Browser) updateWatcher() error {
+	img_type := "webp"
+	if b.serveGif {
+		img_type = "gif"
+	}
+
 	for {
 		select {
 		case up := <-b.updateChan:
 			b.fo.Broadcast(
 				fanout.WebsocketEvent{
-					Type:    fanout.EventTypeWebP,
-					Message: up.WebP,
+					Type:      fanout.EventTypeImage,
+					Message:   up.Image,
+					ImageType: img_type,
 				},
 			)
 
@@ -279,12 +298,12 @@ func (b *Browser) oldRootHandler(w http.ResponseWriter, r *http.Request) {
 		config[k] = vals[0]
 	}
 
-	webp, err := b.loader.LoadApplet(config)
+	img, err := b.loader.LoadApplet(config)
 
 	data := previewData{
 		Title: b.title,
 		Watch: b.watch,
-		WebP:  webp,
+		Image:  img,
 	}
 
 	if err != nil {

server/browser/preview.html

@@ -20,7 +20,7 @@
 
 <body bgcolor="black">
 	<div style="border: solid 1px white">
-		<img id="render" src="data:image/webp;base64,{{ .WebP }}" />
+		<img id="render" src="data:image/{{ .ImageType }};base64,{{ .Image }}" />
 	</div>
 	<div>
 		<p id="errors" style="color: red;">{{ .Err }}</p>
@@ -53,8 +53,8 @@
 				const err = document.getElementById("errors");
 
 				switch (data.type) {
-					case "webp":
-						img.src = "data:image/webp;base64," + data.message;
+					case "img":
+						img.src = "data:image/" + data.img_type + ";base64," + data.message;
 						err.innerHTML = "";
 						break;
 					case "error":

server/browser/push.go

@@ -53,12 +53,12 @@ func (b *Browser) pushHandler(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	webp, err := b.loader.LoadApplet(config)
+	img, err := b.loader.LoadApplet(config)
 
 	payload, err := json.Marshal(
 		TidbytPushJSON{
 			DeviceID:       deviceID,
-			Image:          webp,
+			Image:          img,
 			InstallationID: installationID,
 			Background:     background,
 		},

server/fanout/client.go

@@ -52,7 +52,7 @@ func (f *Fanout) NewClient(conn *websocket.Conn) *Client {
 	return c
 }
 
-// Send is used to send a webp message to the client.
+// Send is used to send an image message to the client.
 func (c *Client) Send(event WebsocketEvent) {
 	c.send <- event
 }
@@ -82,7 +82,7 @@ func (c *Client) reader() {
 	}
 }
 
-// writer writes webp events over the socket when it recieves messages via
+// writer writes image events over the socket when it recieves messages via
 // Send(). It also sends pings to ensure the connection stays alive.
 func (c *Client) writer() {
 	ticker := time.NewTicker(pingPeriod)

server/fanout/event.go

@@ -1,24 +1,27 @@
 package fanout
 
 const (
-	// EventTypeWebP is used to signal what type of message we are sending over
+	// EventTypeImage is used to signal what type of message we are sending over
 	// the socket.
-	EventTypeWebP = "webp"
+	EventTypeImage = "img"
 
 	// EventTypeSchema is used to signal that the schema for a given app has
 	// changed.
 	EventTypeSchema = "schema"
 
 	// EventTypeErr is used to signal there was an error encountered rendering
-	// the WebP image.
+	// the image.
 	EventTypeErr = "error"
 )
 
 // WebsocketEvent is a structure used to send messages over the socket.
 type WebsocketEvent struct {
-	// Message is the contents of the message. This is a webp, base64 encoded.
+	// Message is the contents of the message. This is a webp or gif, base64 encoded.
 	Message string `json:"message"`
 
+	// ImageType indicates whether the Message is webp or gif image.
+	ImageType string `json:"img_type"`
+
 	// Type is the type of message we are sending over the socket.
 	Type string `json:"type"`
 }

server/loader/loader.go

@@ -30,12 +30,14 @@ type Loader struct {
 	maxDuration      int
 	initialLoad      chan bool
 	timeout          int
+	renderGif		 bool
 }
 
 type Update struct {
-	WebP   string
-	Schema string
-	Err    error
+	Image     string
+	ImageType string
+	Schema    string
+	Err       error
 }
 
 // NewLoader instantiates a new loader structure. The loader will read off of
@@ -49,6 +51,7 @@ func NewLoader(
 	updatesChan chan Update,
 	maxDuration int,
 	timeout int,
+	renderGif bool,
 ) (*Loader, error) {
 	l := &Loader{
 		fs:               fs,
@@ -62,6 +65,7 @@ func NewLoader(
 		maxDuration:      maxDuration,
 		initialLoad:      make(chan bool),
 		timeout:          timeout,
+		renderGif:        renderGif,
 	}
 
 	cache := runtime.NewInMemoryCache()
@@ -95,12 +99,16 @@ func (l *Loader) Run() error {
 		case <-l.requestedChanges:
 			up := Update{}
 
-			webp, err := l.loadApplet(config)
+			img, err := l.loadApplet(config)
 			if err != nil {
 				log.Printf("error loading applet: %v", err)
 				up.Err = err
 			} else {
-				up.WebP = webp
+				up.Image = img
+				up.ImageType = "webp"
+				if l.renderGif {
+					up.ImageType = "gif"
+				}
 			}
 
 			l.updatesChan <- up
@@ -109,12 +117,16 @@ func (l *Loader) Run() error {
 			log.Println("detected updates, reloading")
 			up := Update{}
 
-			webp, err := l.loadApplet(config)
+			img, err := l.loadApplet(config)
 			if err != nil {
 				log.Printf("error loading applet: %v", err)
 				up.Err = err
 			} else {
-				up.WebP = webp
+				up.Image = img
+				up.ImageType = "webp"
+				if l.renderGif {
+					up.ImageType = "gif"
+				}
 				up.Schema = string(l.applet.SchemaJSON)
 			}
 
@@ -134,7 +146,7 @@ func (l *Loader) LoadApplet(config map[string]string) (string, error) {
 	l.configChanges <- config
 	l.requestedChanges <- true
 	result := <-l.resultsChan
-	return result.WebP, result.Err
+	return result.Image, result.Err
 }
 
 func (l *Loader) GetSchema() []byte {
@@ -182,12 +194,17 @@ func (l *Loader) loadApplet(config map[string]string) (string, error) {
 	if screens.ShowFullAnimation {
 		maxDuration = 0
 	}
-	webp, err := screens.EncodeWebP(maxDuration)
+
+	var img []byte
+	if l.renderGif {
+		img, err = screens.EncodeGIF(maxDuration)
+	} else {
+		img, err = screens.EncodeWebP(maxDuration)
+	}
 	if err != nil {
 		return "", fmt.Errorf("error rendering: %w", err)
 	}
-
-	return base64.StdEncoding.EncodeToString(webp), nil
+	return base64.StdEncoding.EncodeToString(img), nil
 }
 
 func (l *Loader) markInitialLoadComplete() {

server/server.go

@@ -23,7 +23,7 @@ type Server struct {
 }
 
 // NewServer creates a new server initialized with the applet.
-func NewServer(host string, port int, watch bool, path string, maxDuration int, timeout int) (*Server, error) {
+func NewServer(host string, port int, watch bool, path string, maxDuration int, timeout int, serveGif bool) (*Server, error) {
 	fileChanges := make(chan bool, 100)
 
 	// check if path exists, and whether it is a directory or a file
@@ -47,13 +47,13 @@ func NewServer(host string, port int, watch bool, path string, maxDuration int,
 	}
 
 	updatesChan := make(chan loader.Update, 100)
-	l, err := loader.NewLoader(fs, watch, fileChanges, updatesChan, maxDuration, timeout)
+	l, err := loader.NewLoader(fs, watch, fileChanges, updatesChan, maxDuration, timeout, serveGif)
 	if err != nil {
 		return nil, err
 	}
 
 	addr := fmt.Sprintf("%s:%d", host, port)
-	b, err := browser.NewBrowser(addr, filepath.Base(path), watch, updatesChan, l)
+	b, err := browser.NewBrowser(addr, filepath.Base(path), watch, updatesChan, l, serveGif)
 	if err != nil {
 		return nil, err
 	}