PNG to JPEG — Verify the result

Worked example

Open the downloaded .jpg and check three things: same pixel size as the PNG, plain white where it was transparent, and clean edges.

The file is named after the original with a -convert suffix and a .jpg extension, so logo.png becomes logo-convert.jpg. Look at its properties in your file manager or image viewer. A 1200 × 1200 px source should still read 1200 × 1200, and the type should say JPEG with no alpha channel.

Then judge it the way a visitor will. Place the JPG on a white page and on a coloured page. If a drop shadow, a glow or the fringe of an antialiased logo suddenly shows a pale box or halo, that is the white fill the converter applied, not a download error.

A typical mistake is checking only the thumbnail. Zoom to 200 percent on letters and on any diagonal edge, since JPEG blocking appears there first as fuzzy specks beside the strokes. Compare against the PNG open in a second window at the same zoom.

Finally compare sizes. If the JPG is much larger than a flat PNG, the artwork suits PNG better and you should deliver the original instead. If anything looks off, convert that single file again on its own so you can tell a source problem from a batch problem. Write down both byte counts for future reference.

PNG + alpha

JPEG + opaque background

A .jpg extension alone proves nothing; read the type and dimensions in the file properties before sending it on.