ffmpeg pipe images extracted from video
yes there is!
add the argument -f image2pipe, and specify the output filename as a single hypen (-, in this context it means stdout), and specify the input filename also as a single hypen (-i -, in this context it means stdin) and explicitly specify the output format (eg for png: -c:v png), here is a complete example:
ffmpeg -i - -ss 00:00:3 -s 650x390 -vframes 1 -c:v png -f image2pipe -