How to do convert this ImageMagick command and parameters into a Ruby code to be used with Carrierwave

Basically I am asking how to do this:

convert input.png -bordercolor white -border 1 -set option:distort:viewport "%[fx:max(w,h)]x%[fx:max(w,h)]-%[fx:max((h-w)/2,0)]-%[fx:max((w-h)/2,0)]" -virtual-pixel edge -distort SRT 0 output.png

inside a Carrierwave uploader class.

Note: this command makes rectangular images into squares with white background.

Thank you.

Thanks to Jancko-m at github, he provided the following solution:

MiniMagick::Tool::Convert.new do |cmd|
  convert << "input.png"
  convert.bordercolor("white")
  convert.border("1"),
  convert.set("option:distort:viewport", "%[fx:max(w,h)]x%[fx:max(w,h)]-%[fx:max((h-w)/2,0)]-%[fx:max((w-h)/2,0)]")
  convert.virtual_pixel("edge")
  convert.distort("SRT", "0")
  convert << "output.png"
end