Rewrite JPEG snapshot consumer

internal/ffmpeg/jpeg.go

@@ -12,22 +12,36 @@ import (
 	"github.com/AlexxIT/go2rtc/pkg/shell"
 )
 
-func TranscodeToJPEG(b []byte, query url.Values) ([]byte, error) {
-	ffmpegArgs := parseQuery(query)
-	cmdArgs := shell.QuoteSplit(ffmpegArgs.String())
+func JPEGWithQuery(b []byte, query url.Values) ([]byte, error) {
+	args := parseQuery(query)
+	return transcode(b, args.String())
+}
+
+func JPEGWithScale(b []byte, width, height int) ([]byte, error) {
+	args := defaultArgs()
+	args.AddFilter(fmt.Sprintf("scale=%d:%d", width, height))
+	return transcode(b, args.String())
+}
+
+func transcode(b []byte, args string) ([]byte, error) {
+	cmdArgs := shell.QuoteSplit(args)
 	cmd := exec.Command(cmdArgs[0], cmdArgs[1:]...)
 	cmd.Stdin = bytes.NewBuffer(b)
 	return cmd.Output()
 }
 
-func parseQuery(query url.Values) *ffmpeg.Args {
-	args := &ffmpeg.Args{
+func defaultArgs() *ffmpeg.Args {
+	return &ffmpeg.Args{
 		Bin:    defaults["bin"],
 		Global: defaults["global"],
 		Input:  "-i -",
 		Codecs: []string{defaults["mjpeg"]},
 		Output: defaults["output/mjpeg"],
 	}
+}
+
+func parseQuery(query url.Values) *ffmpeg.Args {
+	args := defaultArgs()
 
 	var width = -1
 	var height = -1