Ruby function to convert 565 & 555 format data into a Magick::Image

create_magick_image.rb

require 'rmagick'

def create_magick_image(input, width, height, bpp)
  mode = 'RGB'
  case bpp
  when 15
    data = input.unpack('v*').collect do |rgb|
      rgb = rgb & 0x7fff
      red = (rgb >> 10) / 31.0
      green = ((rgb >> 5) & 31) / 31.0
      blue = (rgb & 31) / 31.0
      [red, green, blue]
    end
    data = data.flatten
  when 16
    data = input.unpack('v*').collect do |rgb|
      red = (rgb >> 11) / 31.0
      green = ((rgb >> 5) & 63) / 63.0
      blue = (rgb & 31) / 31.0
      [red, green, blue]
    end
    data = data.flatten
  when 32
    mode = 'ARGB'
    data = input.unpack('C*').collect { |p| p / 255.0 }
  else
    raise ArgumentError, "Unsupported bpp: #{bpp}"
  end

  Magick::Image.constitute(width, height, mode, data)
end