Choose this when
The selected Perchance generator shows an image-upload or reference control.
Upload a permitted source image and try a narrow prompt: keep the subject and camera angle, but change the background to a garden.
You can judge whether that particular generator follows the reference. If it changes the subject too much, simplify the request or use a tool built around source images.
Choose this when
The selected generator offers only a text prompt.
Describe the scene if a fresh, similar-looking picture is acceptable; do not expect it to reproduce an unseen photo.
Without access to the original pixels, it has no reliable way to retain a specific face, product label or small composition detail.
Choose this when
You need the original photo to remain recognizable.
Use an image-to-image workflow: supply the photo, state the one change you want, and explicitly list what should stay.
This gives the tool a visual starting point, though you should still inspect identity, hands, text and edges in the result.