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/webp/helpers.go

@@ -0,0 +1,84 @@
+package webp
+
+import (
+	"bytes"
+	"image"
+	"image/jpeg"
+
+	webplib "github.com/skrashevich/go-webp"
+
+	"github.com/AlexxIT/go2rtc/pkg/core"
+	"github.com/AlexxIT/go2rtc/pkg/mjpeg"
+	"github.com/AlexxIT/go2rtc/pkg/y4m"
+	"github.com/pion/rtp"
+)
+
+// EncodeImage encodes any image.Image to WebP lossy bytes.
+func EncodeImage(img image.Image, quality int) ([]byte, error) {
+	buf := bytes.NewBuffer(nil)
+	if err := webplib.Encode(buf, img, &webplib.Options{Lossy: true, Quality: float32(quality)}); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+// EncodeLossless encodes image.Image to WebP lossless bytes.
+func EncodeLossless(img image.Image) ([]byte, error) {
+	buf := bytes.NewBuffer(nil)
+	if err := webplib.Encode(buf, img, &webplib.Options{Lossy: false}); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+// EncodeJPEG converts JPEG bytes to WebP lossy bytes.
+func EncodeJPEG(jpegData []byte, quality int) ([]byte, error) {
+	img, err := jpeg.Decode(bytes.NewReader(jpegData))
+	if err != nil {
+		return nil, err
+	}
+	return EncodeImage(img, quality)
+}
+
+// Decode decodes WebP bytes to image.Image.
+func Decode(data []byte) (image.Image, error) {
+	return webplib.Decode(bytes.NewReader(data))
+}
+
+// FixJPEGToWebP is like mjpeg.FixJPEG but outputs WebP. Handles AVI1 MJPEG frames.
+func FixJPEGToWebP(jpegData []byte, quality int) ([]byte, error) {
+	fixed := mjpeg.FixJPEG(jpegData)
+	return EncodeJPEG(fixed, quality)
+}
+
+// Encoder converts a RAW YUV frame to WebP.
+func Encoder(codec *core.Codec, handler core.HandlerFunc) core.HandlerFunc {
+	newImage := y4m.NewImage(codec.FmtpLine)
+
+	return func(packet *rtp.Packet) {
+		img := newImage(packet.Payload)
+
+		b, err := EncodeImage(img, 75)
+		if err != nil {
+			return
+		}
+
+		clone := *packet
+		clone.Payload = b
+		handler(&clone)
+	}
+}
+
+// JPEGToWebP converts a JPEG frame packet to WebP.
+func JPEGToWebP(handler core.HandlerFunc) core.HandlerFunc {
+	return func(packet *rtp.Packet) {
+		b, err := EncodeJPEG(packet.Payload, 75)
+		if err != nil {
+			return
+		}
+
+		clone := *packet
+		clone.Payload = b
+		handler(&clone)
+	}
+}