Almost got ptx stuff ripping

lib/ptx.ex

@@ -0,0 +1,113 @@
+defmodule Ptx do
+
+  @magic_number << 0x50, 0x54, 0x58, 0x40 >>
+
+  def to_binary(list_of_binaries) do
+    Enum.reduce(list_of_binaries, fn x, acc -> acc <> x end)
+  end
+
+  def parse_ptx(stream) do
+
+    <<
+      magic_number::bitstring-size(32),
+    >> = stream
+         |> Stream.take(0x04)
+        |> to_binary
+
+    if magic_number != @magic_number do
+      {:error, "Does not appear to be a PTX file - magic number did not match"}
+    else
+
+        <<
+          unknown_short1::little-integer-size(16),
+          unknown_short2::little-integer-size(16),
+          width::little-integer-size(16),
+          height::little-integer-size(16),
+          unknown_long::bitstring-size(32),
+          colors::little-integer-size(32),
+          indexing::little-integer-size(8),
+          unknown_short3::little-integer-size(16),
+          unknown_char1::little-integer-size(8),
+          palette_offset::little-integer-size(32),
+          data_offset::little-integer-size(32)
+        >> = stream
+            |> Stream.drop(0x04)
+            |> Stream.take(0x1C)
+            |> to_binary
+
+        palette = parse_palette(stream |> Stream.drop(palette_offset), colors)
+
+
+        unknowns = 
+          %{
+            addr_0x04: unknown_short1,
+            addr_0x06: unknown_short2,
+            addr_0x0C: unknown_long,
+            addr_0x15: unknown_short3,
+            addr_0x17: unknown_char1,
+          }
+
+        %{
+          palette: palette,
+          width: width,
+          height: height,
+          indexing: indexing,
+          data_offset: data_offset,
+          unknowns: unknowns
+        }
+      end
+  end
+
+  def parse_palette(stream, colors) do
+    stream
+    |> Stream.take(colors * 0x04)
+    |> Stream.chunk_every(0x04)
+  end
+
+  def as_png(input_file_name), do: as_png(input_file_name, Path.join(
+  [Path.dirname(input_file_name), 
+    Path.basename(input_file_name, ".ptx") <> ".png"
+  ]))
+  def as_png(input_file_name, output_file_name) do
+    stream = File.stream!(input_file_name, [], 1)
+    info = parse_ptx(stream)
+    as_png(stream, info, output_file_name)
+  end
+  def as_png(stream, info, file_name) do
+    pixel_data = 
+      stream
+      |> Stream.drop(info.data_offset)
+      |> nibble(info.indexing)
+      |> Stream.take(info.width * info.height)
+      |> Enum.to_list
+      |> List.flatten
+      |> to_binary
+
+    case Png.make_png
+      |> Png.with_width(info.width)
+      |> Png.with_height(info.height)
+      |> Png.with_color_type(info.palette |> Enum.to_list())
+      |> Png.with_bgra()
+      |> Png.execute(pixel_data)
+        do
+          {:ok, png_data} -> File.write(file_name, png_data <> <<>>)
+          {:error, err} -> IO.puts(err)
+        end
+
+  end
+
+  def nibble(stream, indexing) do
+    if indexing == 4 do
+      Stream.map(stream, fn byte -> 
+        << 
+          nib2::little-integer-size(4),
+          nib1::little-integer-size(4)
+        >> = byte
+        [ nib1, nib2 ]
+      end)
+    else
+      stream
+    end
+  end
+
+end