Handling transparency correctly
JPEG has no transparency. When a transparent PNG is converted, those areas must be filled with a solid colour or they can render as black. Aimager detects the output is JPEG and lets you pick white, black or a custom background, then composites the image properly.
Why convert PNG to JPG?
Photographs saved as PNG are often 5-10x larger than they need to be. Converting to JPG at quality 85 keeps them looking great while making them far easier to share and upload.