Convert j2k to png Online: j2k2png

You can use Tom's Editor to easily convert images from
JPEG-2000 Code Stream Syntax .J2K to Portable Network Graphics .PNG.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

J2K

JPEG-2000 Code Stream Syntax is an image format with extension J2K.

PNG

Portable Network Graphics is an image format with extension PNG.