Added GIF parsing example.

diff --git a/examples/gif.ml b/examples/gif.ml
new file mode 100644 (file)
index 0000000..050a9c8
--- /dev/null
+++ b/examples/gif.ml
@@ -0,0 +1,33 @@
+(* GIF header parser.
+ * $Id$
+ *)
+
+open Printf
+
+let () =
+  if Array.length Sys.argv <= 1 then
+    failwith "usage: gif input.gif";
+  let filename = Sys.argv.(1) in
+  let bits = Bitmatch.bitstring_of_file filename in
+
+  bitmatch bits with
+  | { ("GIF87a"|"GIF89a") : 6*8 : string; (* GIF magic. *)
+      width : 16 : littleendian;
+      height : 16 : littleendian;
+      colormap : 1;                    (* Has colormap? *)
+      colorbits : 3;                   (* Color res = colorbits+1 *)
+      sortflag : 1;
+      bps : 3;                         (* Bits/pixel = bps+1 *)
+      bg : 8;                          (* Background colour. *)
+      aspectratio : 8 } ->
+      printf "%s: GIF image:\n" filename;
+      printf "  size %d %d\n" width height;
+      printf "  has global colormap? %b\n" colormap;
+      printf "  colorbits %d\n" (colorbits+1);
+      printf "  global colormap is sorted? %b\n" sortflag;
+      printf "  bits/pixel %d\n" (bps+1);
+      printf "  background color index %d\n" bg;
+      printf "  aspect ratio %d\n" aspectratio
+
+  | { _ } ->
+      eprintf "%s: Not a GIF image\n" filename