Hi,

I am going through some tutorials, and I’m trying to generate an Identicon, but Im getting an error when trying to run the program. The program is compiling with no issues, but it looks like it errors when executing :egd.render(image) - when I comment it out there is no error. I had a look at the code and I cannot find anything wrong. EGD has been installed from the git repo.
Error:

09:55:06.606 [error] Process #PID<0.141.0> raised an exception
** (UndefinedFunctionError) function :zlib.crc32/2 is undefined or private
    :zlib.crc32(#Reference<0.1358207439.4254203912.140130>, <<73, 72, 68, 82, 0, 0, 0, 250, 0, 0, 0, 250, 8, 2, 0, 0, 0>>)
    (egd 0.10.0) d:/Dropbox/Projects/Programming/Elixir/maps/deps/egd/src/egd_png.erl:102: :egd_png.create_chunk/2
    (egd 0.10.0) d:/Dropbox/Projects/Programming/Elixir/maps/deps/egd/src/egd_png.erl:72: :egd_png.bitmap2png/4
    (egd 0.10.0) d:/Dropbox/Projects/Programming/Elixir/maps/deps/egd/src/egd_png.erl:62: :egd_png.binary/3
    (egd 0.10.0) d:/Dropbox/Projects/Programming/Elixir/maps/deps/egd/src/egd.erl:240: :egd.loop/1
** (EXIT from #PID<0.140.0>) shell process exited with reason: an exception was raised:
    ** (UndefinedFunctionError) function :zlib.crc32/2 is undefined or private
        :zlib.crc32(#Reference<0.1358207439.4254203912.140130>, <<73, 72, 68, 82, 0, 0, 0, 250, 0, 0, 0, 250, 8, 2, 0, 0, 0>>)
        (egd 0.10.0) d:/Dropbox/Projects/Programming/Elixir/maps/deps/egd/src/egd_png.erl:102: :egd_png.create_chunk/2
        (egd 0.10.0) d:/Dropbox/Projects/Programming/Elixir/maps/deps/egd/src/egd_png.erl:72: :egd_png.bitmap2png/4
        (egd 0.10.0) d:/Dropbox/Projects/Programming/Elixir/maps/deps/egd/src/egd_png.erl:62: :egd_png.binary/3
        (egd 0.10.0) d:/Dropbox/Projects/Programming/Elixir/maps/deps/egd/src/egd.erl:240: :egd.loop/1

Program:

defmodule Maps do
  def main(input) do
    input
    |> hashstring
    |> pick_color
    |> build_grid
    |> filter_odd
    |> build_pixel_map
    |> draw_image
    |> save_image(input)
  end

  def save_image(image, input) do
    File.write("#{input}.png", image)
  end

  def draw_image(%Identicon.Image{color: color, pixel_map: pixel_map}) do
    image = :egd.create(250, 250)
    fill = :egd.color(color)

    Enum.each pixel_map, fn({start, stop}) ->
      :egd.filledRectangle(image, start, stop, fill)
    end

    :egd.render(image)
  end

  def build_pixel_map(%Identicon.Image{grid: grid} = image) do
    pix_map = Enum.map grid, fn({_code, index}) ->
      horizontal = rem(index, 5) *50
      vertical = div(index, 5) *50

      top_left = {horizontal, vertical}
      bottom_right = {horizontal+50, vertical+50}

      {top_left, bottom_right}
    end

    %Identicon.Image{image | pixel_map: pix_map}
  end

  def filter_odd(%Identicon.Image{grid: grid} = image) do
    grid = Enum.filter grid, fn({code, _index}) ->
      rem(code, 2) == 0
    end

    %Identicon.Image{image | grid: grid}
  end

  def build_grid(%Identicon.Image{hex: hex}= image) do
    grid =
      hex
      |> Enum.chunk_every(3, 2, :discard)
      |> Enum.map(&mirror_row/1)
      |> List.flatten
      |> Enum.with_index

    %Identicon.Image{image | grid: grid}
  end

  def mirror_row(row) do
    # [123, 34, 22]
    [first, second | _tail] = row

    # [123, 34, 22, 34, 123]
    row ++ [second, first]
  end

  def pick_color(%Identicon.Image{hex: [red, green, blue | _tail]} = image) do
    %Identicon.Image{image | color: {red, green, blue}}
  end

  def hashstring(string) do
    hex =  :crypto.hash(:md5, string)
    |> :binary.bin_to_list

    %Identicon.Image{hex: hex}
  end
end
'''
Struct:

defmodule Identicon.Image do
defstruct hex: nil, color: nil, grid: nil, pixel_map: nil
end

Thanks.

The :egd