JPEG to PNG — Verify the result

Worked example

Compare the downloaded .png with the original JPEG: same dimensions, identical look at 100 percent, and a larger file size.

The result is named after the source with -convert added, so beach.jpg becomes beach-convert.png. Open both files in a viewer that shows properties. The pixel dimensions must match exactly, for example 3000 × 2000 px in and 3000 × 2000 px out, because this conversion does not resize.

Put the two images side by side at 100 percent and flip between them over a patch of sky or skin. They should look identical. If you can see a difference in colour, the viewer is probably treating colour profiles differently, not the converter damaging the image, so try a second viewer before you worry.

A typical mistake is expecting the PNG to look better, then deciding the conversion failed because it still shows blocky shadows. That is the JPEG's damage, preserved on purpose. What you should confirm instead is that the PNG has no new artifacts and no stripes.

Finally read the size. A PNG several times larger than the JPEG is expected. If it is smaller, you probably opened a different file than the one you meant to convert. If anything looks off, repeat the conversion with that single file on its own to separate a source problem from a batch problem.

JPEG photo

PNG still image

Identical pixels, not an improved picture, is the correct result; judge the PNG against the JPEG, not against an ideal photo.