How to Read and write metadata from/to jpeg/png image from qml/qt?

Hi Can anyone tell me what are the methods available for reading and writing metadata in qml/qt? I need to write thumbnail image to jpeg image from qml? How do i do? I have checked with setMetadata(key,value). i could write only few parameters such as make,description…Now i need to write thumbnail.How do i do? Thanks in advance Bala Beemaneni