Blitline supports the extraction of keyframes from video files.
The video formats that are supported are: avi, mov, mp4, mpeg, mpg, 3gp, as, flv, swf, m4v , webm
To extract keyframes, simply denote pages your wish to extract from the video file. The pages indicate offset in seconds from the beginning of the video. So, for example, page 0 would be the initial image at 0 seconds, page 1 would be the frame at 1 second, etc.
So for example:
The above JSON would generate an image of the video frame at 1 second into the video, then resize it to fit within 300 pixels.
See live example here: