[update]
We have just released v1.9.6 Beta with Methods & Properties, which allows you to programmatically export chart as image, print chart, access internally calculated values, etc. Please refer to the release blog for more information.
Mitul,
You can hide ‘save as PNG’ using CSS. Here is an example.
You can also have a button/link outside chart to export it as JPEG, using dataURL. Here is an example.