langs a-z

Task/Bitmap-Histogram/OCaml/bitmap-histogram-1.ocaml

@@ -0,0 +1,14 @@
+type histogram = int array
+
+let get_histogram ~img:gray_channel =
+  let width = Bigarray.Array2.dim1 gray_channel
+  and height = Bigarray.Array2.dim2 gray_channel in
+  let t = Array.make 256 0 in
+  for x = 0 to pred width do
+    for y = 0 to pred height do
+      let v = gray_get_pixel_unsafe gray_channel x y in
+      t.(v) <- t.(v) + 1;
+    done;
+  done;
+  (t: histogram)
+;;

Task/Bitmap-Histogram/OCaml/bitmap-histogram-2.ocaml

@@ -0,0 +1,15 @@
+let histogram_median (h : histogram) =
+
+  let from = 0 and to_ = 255 in
+  let left = h.(from) and right = h.(to_) in
+
+  let rec aux from to_ left right =
+    if from = to_
+    then (from)
+    else
+      if left < right
+      then aux (succ from) to_ (left + h.(from)) right
+      else aux from (pred to_) left (right + h.(to_))
+  in
+  aux from to_ left right
+;;

Task/Bitmap-Histogram/OCaml/bitmap-histogram-3.ocaml

@@ -0,0 +1,24 @@
+let () =
+  let img = read_ppm ~filename:"/tmp/foo.ppm" in
+
+  let width, height = get_dims img in
+  let res = new_img ~width ~height in
+
+  let g_img = to_grayscale ~img in
+  let h = get_histogram g_img in
+  let m = histogram_median h in
+
+  let light = (255, 255, 0)
+  and dark = (127, 0, 127) in
+
+  for x = 0 to pred width do
+    for y = 0 to pred height do
+      let v = gray_get_pixel_unsafe g_img x y in
+      if v > m
+      then put_pixel_unsafe res light x y
+      else put_pixel_unsafe res dark x y
+    done;
+  done;
+
+  output_ppm ~oc:stdout ~img:res;
+;;