(library (linux libgd)
  (export gd-image-create
          gd-image-destroy
          gd-image-color-allocate
          gd-image-line
          gd-image-rectangle
          gd-image-png-ptr
          gd-free)
  (import (rnrs) (ffi))

  (define libgd-name "libgd.so.2")
  (define libgd (load-shared-object libgd-name))
  (define gd-image-create (c-function libgd libgd-name void* gdImageCreate (int int)))
  (define gd-image-destroy (c-function libgd libgd-name void gdImageDestroy (void*)))
  (define gd-image-color-allocate (c-function libgd libgd-name int gdImageColorAllocate (void* int int int)))
  (define gd-image-rectangle (c-function libgd libgd-name void gdImageRectangle (void* int int int int int)))
  (define gd-image-line (c-function libgd libgd-name void gdImageLine (void* int int int int int)))
  (define gd-image-png-ptr (c-function libgd libgd-name void* gdImagePngPtr (void* byte*)))
  (define gd-free (c-function libgd libgd-name void gdFree (void*)))
)

(import (ffi) (linux libgd))
(let ((im (gd-image-create 100 100)))
  (gd-image-color-allocate im #xff #xff #xff) ; background color
  (let ((c (gd-image-color-allocate im #xff #x00 #x00)))
    (gd-image-rectangle im 20 20 80 80 c)
    (gd-image-line im 20 80 80 20 c))
  (let* ((bsize (make-bytevector sizeof:int))
         (ptr (gd-image-png-ptr im bsize))
         (size (bytevector-c-int-ref bsize 0))
         (bvector (make-bytevector-mapping ptr size)))
    (let ((oport (open-file-output-port "square.png")))
      (put-bytevector oport bvector)
      (close-port oport))
    (gd-free ptr)
    )
  (gd-image-destroy im)
)