A reference image is a visual input used to guide an image model while it generates or edits another image. Authors can use a character sketch to suggest a figure’s broad appearance, a palette board to guide color, or a composition reference to influence a cover layout.
Image tools may offer different reference modes for subject, style, composition, or direct editing. The names and effects vary. Midjourney distinguishes Image Prompts from Style References and its Editor; it describes Image Prompts as inspiration for a new image rather than an exact copy. Its image-weight setting changes how strongly the reference influences a result, and available ranges vary by model version (Image Prompts documentation, checked 3 October 2026).
A reference is guidance, not a fidelity guarantee. Small details, layout, text, and a character’s appearance can change, so repeated references do not ensure an identical face or identity across a book series. For precise changes to an existing image, use an editing mode where the tool provides one; for broader art direction, describe the details that matter alongside the reference.