There are two functions applications can use to capture an image:
An application uses MCI_GETIMAGEBUFFER to capture an image when it wants to keep the image in an application buffer. The application can capture the image from either a movie file, or the buffer of a video capture card. This command message returns the image in the format specified by the application.
An application uses MCI_CAPTURE to capture an image from a movie file when it wants the image kept in a digital video device element.