Manipulating a base64 string

[Binh GIIK]

I know this is a stupid question but has anyone have a luck to manipulate a base64string on Node Server side without OS dependencies of Cairo, canvas, and in-memory graphic?

I'm building a Node app on Server side that requires to draw a blur box on an original base64string as an input, the output will be a new base64 string. I know that this can be done on client with HTML5's canvas 2dContext with 3 lines of code fillRect, and fillStyle, and it can be done on iOS cocoa/swift with CGContextFillRect, CGRectMake(x,y,w,h)

Any help is very appreciated.