Using Ruby's RMagick to process (crop and/or resize) an image given simple inputs (new ratio/size)

uniform_image.rb

#!/usr/bin/env ruby

require "rmagick"

# Define class UniformImage
class UniformImage
  def initialize(image, suffix="_uniform", extension="jpg")
    # Instance variables
    @image = image
    if self.exists?
      @image_open = Magick::Image::read(@image).first
    else
      @image_open = Magick::Image::new(100, 100)
    end
    @image_processed = @image_open
    @image_suffix = suffix
    @image_extension = extension
  end

  def exists?
    File.file?(@image)
  end

  def print_info
    puts @image
    @image_open = Magick::Image::read(@image).first
    puts "   Format: #{@image_open.format}"
    puts "   Geometry: #{@image_open.columns}x#{@image_open.rows}"
    puts "   Class: " + case @image_open.class_type
                            when Magick::DirectClass
                                "DirectClass"
                            when Magick::PseudoClass
                                "PseudoClass"
                        end
    puts "   Depth: #{@image_open.depth} bits-per-pixel"
    puts "   Colors: #{@image_open.number_colors}"
    puts "   Filesize: #{@image_open.filesize}"
    puts "   Resolution: #{@image_open.x_resolution.to_i}x#{@image_open.y_resolution.to_i} "+
        "pixels/#{@image_open.units == Magick::PixelsPerInchResolution ?
        "inch" : "centimeter"}"
  end

  def columns
    @image_processed.columns.to_f
  end

  def rows
    @image_processed.rows.to_f
  end

  def orientation
    # 0 Portrait
    # 1 Landscape
    self.columns() > self.rows() ? 0 : 1
  end

  def aspect_ratio
    self.columns() / self.rows()
  end

  def crop_to_aspect_ratio(new_ratio)
    new_ratio_arr = new_ratio.split(":")
    cols = new_ratio_arr[0].to_f
    rows = new_ratio_arr[1].to_f
    r2 = cols / rows
    x1 = self.columns()
    y1 = self.rows()
    r1 = self.aspect_ratio
    if r1 < r2
      x2 = x1
      y2 = (y1 * r1 / r2).ceil
    else
      x2 = (x1 * r2 / r1).ceil
      y2 = y1
    end
    @image_processed = @image_processed.crop(Magick::CenterGravity, x2, y2, true)
  end

  def resize(new_size)
    new_size_arr = new_size.split("x")
    cols = new_size_arr[0].to_f
    rows = new_size_arr[1].to_f
    @image_processed = @image_processed.resize_to_fit(cols, rows)
  end

  def crop_and_resize(new_size)
    new_size_arr = new_size.split("x")
    cols = new_size_arr[0].to_f
    rows = new_size_arr[1].to_f
    new_ratio = "#{cols}:#{rows}"
    self.crop_to_aspect_ratio(new_ratio)
    self.resize(new_size)
  end

  def new_name
    name = @image.split(".")
    filename = name[0]
    extension = @image_extension || name[1] || "jpg"
    "#{filename}#{@image_suffix}.#{extension}"
  end

  def save
    @image_processed.write(self.new_name)
  end
end

# Examples
me = UniformImage.new("example.jpg")
me.crop_to_aspect_ratio("3:2")
me.resize("300x300")
me.save()

her = UniformImage.new("example2.jpg")
her.crop_to_aspect_ratio("2:3")
her.resize("300x300")
her.save()

him = UniformImage.new("example3.jpg")
him.crop_and_resize("200x300")
him.save()