Automatic GIF, Thumbnail, video preview Maker


Hope, I’m in the right Thread with my question.

I’m looking for a tool that automatically creates GIFs from a video. Or maybe also thumbnails or previews. By automatic I mean that I don’t have to manually select the position in a video from which I want to create a GIF (or thumbnail or a preview). I imagine uploading a video (don’t want a online tool for that) and telling the program how long a GIF, thumbnail or video preview should be and the program automatically creates it from the video in the length I want.

Are there any suggestions? Thank you very much for your answers.