What scaleImage is told of the image it scales, which
scalableImage (lib/upload.ts) reads from its first bytes.
orientation: number
The EXIF orientation to turn the image by, 1 when it is upright.
animated: boolean
Whether its frames are an animation, as a GIF's are. A still may hold more than one image too, a phone's JPEG carrying a gain map or a depth map after the photo, and ffmpeg reads each as a frame.