PIxels appearing on background when zooming on topics



I am creating a new Prezi next and I have uploaded an image as the background. I want to create topics that zooms on some parts of this image. However, when the zoom appears, the image quality is quite bad and you can see the pixels. How can we change that? Is there a special quality of image to respect?

Thank you in advance for your reply,
Best regards,



@Caroline_PERDRIEL Could you send us the link of the presentation in question so we can check what exactly happens? Thanks in advance!