resize_images.rb

require 'pathname' 
ROOT = Pathname.pwd

SIZES = %W[
    1056x792
    1162x871
    1278x958
    1406x1054
    1546x1160
    1701x1276
    1871x1403
    2058x1543
    2264x1698
    2490x1867
]

FILES = Dir["*.png"] | Dir["*.jpeg"]

FILES.each do |file_name|
    out_dir = ROOT.join("#{file_name}-sample")
    out_dir.mkpath unless out_dir.exist?

    SIZES.each do |size|
        `convert #{file_name} -resize #{size} #{out_dir.join("#{size}.png")}`
        `convert #{file_name} -resize #{size} #{out_dir.join("#{size}.jpeg")}`
    end
end