without compromising the quality.
any good and free software online?
If you mean "enlarging a bitmap while preserving its clarity and
sharpness", it's not possible. An enlarged image would only contain
as much details as the original one, so it would appear pixelated
or blur due to a lower spatial resolution (same amount of details
displayed over a larger area).
You can try converting it into a SVG (vector) and then enlarge
the image (using Photoshop/Illustrator/GIMP), but I doubt it would
turn out well.
