Fix JPEG from mjpg-streamer project

internal/mjpeg/init.go

@@ -57,6 +57,8 @@ func handlerKeyframe(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 		log.Debug().Msgf("[mjpeg] transcoding time=%s", time.Since(ts))
+	case core.CodecJPEG:
+		b = mjpeg.FixJPEG(b)
 	}
 
 	h := w.Header()

pkg/mjpeg/helpers.go

@@ -0,0 +1,35 @@
+package mjpeg
+
+import (
+	"bytes"
+	"image/jpeg"
+)
+
+// FixJPEG - reencode JPEG if it has wrong header
+//
+// for example, this app produce "bad" images:
+// https://github.com/jacksonliam/mjpg-streamer
+//
+// and they can't be uploaded to the Telegram servers:
+// {"ok":false,"error_code":400,"description":"Bad Request: IMAGE_PROCESS_FAILED"}
+func FixJPEG(b []byte) []byte {
+	// skip non-JPEG
+	if len(b) < 10 || b[0] != 0xFF || b[1] != 0xD8 {
+		return b
+	}
+	// skip if header OK for imghdr library
+	// https://docs.python.org/3/library/imghdr.html
+	if string(b[2:4]) == "\xFF\xDB" || string(b[6:10]) == "JFIF" || string(b[6:10]) == "Exif" {
+		return b
+	}
+
+	img, err := jpeg.Decode(bytes.NewReader(b))
+	if err != nil {
+		return b
+	}
+	buf := bytes.NewBuffer(nil)
+	if err = jpeg.Encode(buf, img, nil); err != nil {
+		return b
+	}
+	return buf.Bytes()
+}