Great work ! Thanks !

By the way, I found a quick and easy way to solve the texture repetition and croping problem :

require "rubygems"
require "gosu"
require "opengl"
include Gl, Glu

class GLTexture
  # GOSU IMAGE -> OPENGL TEXTURE FIX
  # SOLVES PROBLEM WITH REPETITION / CROPING
  def initialize(p_win, filename)
    gosu_image = Gosu::Image.new(p_win, filename, true)
    array_of_pixels = gosu_image.to_blob
    @texture_id = glGenTextures(1)
    glBindTexture(GL_TEXTURE_2D, @texture_id[0])
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, gosu_image.width, gosu_image.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, array_of_pixels)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)
    gosu_image = nil
  end
 
  def get_id
    return @texture_id[0]
  end
end

That way I can easily get a proper texture id and use it in an OpenGL drawing. All that thanks to your new method, Gosu::Image#to_blob ! So, again, thank you !