Added scene preview generator

ffmpeg/encoder_screenshot.go

@@ -0,0 +1,32 @@
+package ffmpeg
+
+import "fmt"
+
+type ScreenshotOptions struct {
+	OutputPath string
+	Quality int
+	Time float64
+	Width int
+	Verbosity string
+}
+
+func (e *Encoder) Screenshot(probeResult VideoFile, options ScreenshotOptions) {
+	if options.Verbosity == "" {
+		options.Verbosity = "quiet"
+	}
+	if options.Quality == 0 {
+		options.Quality = 1
+	}
+	args := []string{
+		"-v", options.Verbosity,
+		"-ss", fmt.Sprintf("%v", options.Time),
+		"-y",
+		"-i", probeResult.Path, // TODO: Wrap in quotes?
+		"-vframes", "1",
+		"-q:v", fmt.Sprintf("%v", options.Quality),
+		"-vf", fmt.Sprintf("scale=%v:-1", options.Width),
+		"-f", "image2",
+		options.OutputPath,
+	}
+	_, _ = e.run(probeResult, args)
+}