------------------------------------------------------------------------------
--  File:            PPM2Func.adb
--  Description:     .PPM / .PGM -> Ada function
--
--  Transforms a PPM (Portable pixelmap) RGB image or
--  a PGM (Portable greymap) into an Ada 'greyscale' function
--  f(x,y) with values in [0,1] and arguments (x,y) in R x R.
--  The image stands in the [0,1] x [0,1] square. Elsewhere, values are 0.
--
--  Syntax: ppm2func input_file function_name
--
--  Author:          G. de Montmollin
--  Version:         5-Sep-2007; 25-Apr-2001
------------------------------------------------------------------------------

with Ada.Command_Line;                  use Ada.Command_Line;
with Ada.Text_IO;                       use Ada.Text_IO;
with Ada.Integer_Text_IO;               use Ada.Integer_Text_IO;
with Ada.Float_Text_IO;                 use Ada.Float_Text_IO;

procedure PPM2Func is

  i, o : File_Type;
  mx, my, R, G, B : Integer;
  v : Float;

  Unknown_Format : exception;

  s : String (1 .. 100);

  l : Natural;

  RGB : Boolean;

  Maxval : Natural;

begin
  if Argument_Count < 2 then
    Put_Line ("Transforms a PPM (Portable pixelmap) RGB image or");
    Put_Line ("a PGM (Portable greymap) into an Ada 'greyscale' function");
    Put_Line ("f(x,y) with values in [0,1] and arguments (x,y) in R x R.");
    Put_Line ("The image stands in the [0,1] x [0,1] square.");
    Put_Line ("Elsewhere, values are 0.");
    New_Line;
    Put_Line ("Syntax: ppm2func input_file function_name");
  else
    Open (i, In_File, Argument (1));
    Get_Line (i, s, l);

    if l /= 2 or else s (1) /= 'P' then
      raise Unknown_Format;
    end if;

    case s (2) is
      when '3' => RGB := True;   --  Pixelmap
      when '2' => RGB := False;  --  Greymap
      when others => raise Unknown_Format;
    end case;

    --  Eventual comment like: # Created by Paint Shop Pro
    Get_Line (i, s, l);
    if l > 0 and then s (1) = '#' then
      null;  --  just go on
    else
      --  We ate a line too much
      Close (i);
      Open (i, In_File, Argument (1));
      Skip_Line (i);
    end if;

    Get (i, mx);
    Get (i, my);
    Get (i, Maxval);

    Create (o, Out_File, Argument (2) & ".adb");

    Put_Line (o, "function " & Argument (2) &
                 " (x, y : Float) return Float is");
    Put_Line (o, "  --  Output of graphic converter ppm2func.");
    Put (o, "  --  Image size & maximum value: ");
    Put (o, mx, 0); Put (o, " x ");
    Put (o, my, 0); Put (o, " x ");
    Put (o, Maxval, 0);
    Put_Line (o, "  RGB: " & Boolean'Image (RGB) & '.');
    Put_Line (o, "  --  The image stands in the [0,1] x [0,1] square, with");
    Put_Line (o, "  --  values in the [0,1] range. Elsewhere, values are 0.");

    Put (o, "  a : constant array (0 .. ");
    Put (o, my - 1, 0);
    Put (o, ", 0 .. ");
    Put (o, mx - 1, 0);
    Put_Line (o, ") of Float :=");

    Put_Line (o, "  (");
    for y in 1 .. my loop
      Put (o, "   (");
      for x in 1 .. mx loop
        Get (i, R);
        if RGB then
          Get (i, G);
          Get (i, B);
        else
          G := R;
          B := R;
        end if;
        v := (Float (R) + Float (G) + Float (B)) / (Float (Maxval) * 3.0);
        Put (o, v, 2, 3, 0);
        if x < mx then Put (o, ','); end if;
        if x mod (75 / 7) = 0 then New_Line (o); Put (o, "    "); end if;
      end loop;
      Put (o, ')');
      if y < my then Put (o, ','); end if;
      New_Line (o);
    end loop;
    Close (i);

    Put_Line (o, "  );");
    New_Line (o);
    Put_Line (o, "begin");
    Put_Line (o, "  if x < 0.0 or else x > 1.0 or else y < 0.0 or else y > 1.0 then");
    Put_Line (o, "    return 0.0;");
    Put_Line (o, "  else");
    Put (o,     "    return a (Integer((1.0 - y) * Float (");
    Put (o, my - 1, 0);
    Put_Line (o, ")),");
    Put (o,     "              Integer       (x  * Float (");
    Put (o, mx - 1, 0);
    Put_Line (o, ")));");
    Put_Line (o, "  end if;");
    Put_Line (o, "end " & Argument (2) & ';');
    Close (o);
  end if;
end PPM2Func;