Use the input image of a real person.
Preserve the same person identity, age, skin tone, facial proportions, hairstyle, head position, body pose, clothing, background, lighting, shadows, highlights, and overall image composition.
Modify ONLY the facial expression through natural and realistic facial muscle movement.
Do NOT change face shape, head size, jawline, eye size, nose size, or lip thickness.
Do NOT add any new facial features.
Allow subtle and necessary micro-adjustments of facial muscles required for the target expression, while keeping the person clearly recognizable.
The result must be photorealistic, natural, seamless, and artifact-free.
No face warping, no plastic skin, no exaggerated emotion, no cartoon-like deformation.