module Genimg_loader:Generic image loadersig..end
If the image to load is known to be a jpeg or a png, you should
use the specialised modules Jpeg_loader, Png_loader and
Svg_loader instead which will be far more efficient.
val load_img : GL.img_input ->
GL.image_data * int * int * GL.InternalFormat.internal_format *
GL.pixel_data_formatwidth and height