feat(webp): add WebP streaming and snapshot APIs

- implement WebP streaming with multipart support
- add snapshot endpoint for WebP format with quality options
- introduce WebP encoding using pure Go library without FFmpeg
- update documentation and links for new WebP features

pkg/image/producer.go

@@ -1,13 +1,16 @@
 package image
 
 import (
+	"bytes"
 	"errors"
+	"image/jpeg"
 	"io"
 	"net/http"
 
 	"github.com/AlexxIT/go2rtc/pkg/core"
 	"github.com/AlexxIT/go2rtc/pkg/tcp"
 	"github.com/pion/rtp"
+	webp "github.com/skrashevich/go-webp"
 )
 
 type Producer struct {
@@ -49,6 +52,12 @@ func (c *Producer) Start() error {
 		return err
 	}
 
+	if isWebP(body) {
+		if converted, err2 := webpToJPEG(body); err2 == nil {
+			body = converted
+		}
+	}
+
 	pkt := &rtp.Packet{
 		Header:  rtp.Header{Timestamp: core.Now90000()},
 		Payload: body,
@@ -74,6 +83,12 @@ func (c *Producer) Start() error {
 			return err
 		}
 
+		if isWebP(body) {
+			if converted, err2 := webpToJPEG(body); err2 == nil {
+				body = converted
+			}
+		}
+
 		c.Recv += len(body)
 
 		pkt = &rtp.Packet{
@@ -90,3 +105,23 @@ func (c *Producer) Stop() error {
 	c.closed = true
 	return c.Connection.Stop()
 }
+
+// isWebP returns true if data starts with RIFF....WEBP magic bytes.
+func isWebP(data []byte) bool {
+	return len(data) >= 12 &&
+		data[0] == 'R' && data[1] == 'I' && data[2] == 'F' && data[3] == 'F' &&
+		data[8] == 'W' && data[9] == 'E' && data[10] == 'B' && data[11] == 'P'
+}
+
+// webpToJPEG decodes WebP bytes and re-encodes as JPEG.
+func webpToJPEG(data []byte) ([]byte, error) {
+	img, err := webp.Decode(bytes.NewReader(data))
+	if err != nil {
+		return nil, err
+	}
+	var buf bytes.Buffer
+	if err = jpeg.Encode(&buf, img, nil); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}