php - FFMPEG watermark scale -

im trying set watermark scale 0.9 or 0.7 , ... how code?

exec("ffmpeg -i file.mp4 -i logo.png \ -filter_complex \"overlay=x=(main_w-overlay_w)/2:y=(main_h-overlay_h)/2\" watermarked.mp4"); 

use command scale watermark 70%:

ffmpeg -i file.mp4 -i logo.png -filter_complex \       "[1]scale=iw*0.7:-1[wm];[0][wm]overlay=x=(w-w)/2:y=(h-h)/2" watermarked.mp4 

---

to change opacity of png logo, use

ffmpeg -i file.mp4 -i logo.png -filter_complex \       "[1]colorchannelmixer=aa=0.5,scale=iw*0.7:-1[wm];[0][wm]overlay=x=(w-w)/2:y=(h-h)/2" watermarked.mp4