fixed the lint issue

Refactor the code to match the oop mode for easy mock and test

add the fit options to scale the image to fit the screen

add reverse options

add convert examples

Revert "add parallel convert"

This reverts commit 6ee682ae1c41bfd64968d71334d72b52c8d29ca3.

add parallel convert

Add some comments

Add ScaleImage and Image2ASCII benchmark

fixed test

fixed the issue

add convert test case