impl ffmpeg.screenshot too

src-lib/src/ffmpeg.rs

@@ -16,6 +16,22 @@ fn clip(output: &String, input: &String, start: f32, stop: f32) -> Result<(), St
    }
 }
 
+fn screenshot(output: &String, input: &String, ts: f32) -> Result<(), String> {
+   match std::process::Command::new("ffmpeg")
+      .args([
+         "-y",
+         "-ss", &ts.to_string(),
+         "-i", input,
+         "-frames:v", "1",
+         "-q:v", "2",
+         output,
+      ])
+      .output() {
+      Ok(_) => Ok(()),
+      Err(msg) => Err(format!("failed to ffmpeg screenshot {}: {}", input, msg)),
+   }
+}
+
 fn inspect(file: &String) -> Result<Inspection, String> {
    match std::process::Command::new("ffmpeg")
       .args([
@@ -178,6 +194,21 @@ mod test_inspection {
    use super::*;
    const FILE: &str = "/Users/breel/Movies/bel_1_1.mp4";
 
+   #[test]
+   fn test_screenshot() {
+      let output = format!("{}.clipped.jpg", FILE);
+      screenshot(
+         &output,
+         &FILE.to_string(),
+         3.0,
+      ).unwrap();
+
+      let inspection = inspect(&output);
+      assert_eq!(true, inspection.is_ok());
+      let inspection = inspection.unwrap();
+      assert_eq!(0.04, inspection.duration());
+   }
+
    #[test]
    fn test_clip() {
       let output = format!("{}.clipped.mp4", FILE);