PNG File Generator

The image is drawn by the browser itself, so the result is a real PNG: viewers open it, and the frame size is visible inside. The field has a grid on it — with the grid you can spot at once if a processor has cropped or stretched the image.

How the size is reached

The extra bytes go into a service chunk that the format itself provides, with the checksum recalculated. You cannot just append bytes to the end: the file would fail the integrity check, and strict viewers would reject it.

The frame and the file size are set separately. A 64×48 image weighing a megabyte is a common test case: the frame is tiny, the weight is heavy, and processors often fail on that combination.