Convert png to ithmb Online: png2ithmb
You can use Tom's Editor to easily convert images from
Portable Network Graphics .PNG to iPod Thumbnail
Tom's Editor is a free, online image manipulation and converter program.
Go to Tom's Editor
Portable Network Graphics is an image format with extension PNG.
ITHMB are thumbnails used by various Apple devices. At first these images were used by iPhods but now can be found on iPhones and iPads.