Handling transparent pixels in JPEG
The PNG format supports an alpha channel that allows pixels to be completely or partially transparent. JPEG, by specification, does not support transparency at all.
When converting a transparent PNG to JPEG, those transparent regions must be rendered against a solid color. Many poorly designed converters mistakenly render transparent areas as solid black boxes. NexoPixel defaults to clean white (#FFFFFF) and provides an interactive color picker so you can specify any exact background tone required.