Bitmap/Bresenham's line algorithm

Bitmap/Bresenham's line algorithm
You are encouraged to solve this task according to the task description, using any language you may know.

Using the data storage type defined on this page for raster graphics images, draw a line given 2 points with the Bresenham's algorithm (definition on Wikipedia).

Ada

<ada> procedure Line (Picture : in out Image; Start, Stop : Point; Color : Pixel) is

  DX  : constant Float := abs Float (Stop.X - Start.X);
  DY  : constant Float := abs Float (Stop.Y - Start.Y);
  Err : Float;
  X   : Positive := Start.X;
  Y   : Positive := Start.Y;
  Step_X : Integer := 1;
  Step_Y : Integer := 1;

begin

  if Start.X > Stop.X then
     Step_X := -1;
  end if;
  if Start.Y > Stop.Y then
     Step_Y := -1;
  end if;
  if DX > DY then
     Err := DX / 2.0;
     while X /= Stop.X loop
        Picture (X, Y) := Color;
        Err := Err - DY;
        if Err < 0.0 then
           Y := Y + Step_Y;
           Err := Err + DX;
        end if;
        X := X + Step_Y;
     end loop;
  else
     Err := DY / 2.0;
     while Y /= Stop.Y loop
        Picture (X, Y) := Color;
        Err := Err - DX;
        if Err < 0.0 then
           X := X + Step_X;
           Err := Err + DY;
        end if;
        Y := Y + Step_Y;
     end loop;
  end if;
  Picture (X, Y) := Color; -- Ensure dots to be drawn

end Line; </ada> The test program's <ada>

  X : Image (1..16, 1..16);

begin

  Fill (X, White);
  Line (X, ( 1, 8), ( 8,16), Black);
  Line (X, ( 8,16), (16, 8), Black);
  Line (X, (16, 8), ( 8, 1), Black);
  Line (X, ( 8, 1), ( 1, 8), Black);
  Print (X);

</ada> sample output

       H
      H H
     H   H
    H     HH
   H        H
  H          H
 H            H
H              H
 H            H
  H          H
   H        H
    H      H
    H     H
     H   H
      H H
       H

C

<C>#define plot(x, y) put_pixel_clip(img, x, y, r, g, b)

1. define swap_uint(a, b) do{ unsigned int tmp; tmp = a; a = b; b = tmp; }while(0)

void draw_line(

       image img,
       unsigned int x0, unsigned int y0,
       unsigned int x1, unsigned int y1,
       color_component r,
       color_component g,
       color_component b )

{

   unsigned short steep;
   steep = abs(y1 - y0) > abs(x1 - x0);
   if (steep) {
       swap_uint(x0, y0);
       swap_uint(x1, y1);
   }
   if (x0 > x1) {
       swap_uint(x0, x1);
       swap_uint(y0, y1);
   }
   {
       int deltax = x1 - x0;
       int deltay = abs(y1 - y0);
       int error = deltax / 2;
       int ystep;
       int y = y0;
       int x;
       if (y0 < y1) ystep = 1; else ystep = -1;
       for (x = x0; x <= x1; ++x) {
           if (steep) plot(y,x); else plot(x,y);
           error = error - deltay;
           if (error < 0) {
               y = y + ystep;
               error = error + deltax;
           }
       }
   }

}

1. undef swap_uint
2. undef plot</C>

MAXScript

fn plot img coord steep col =
(
    if steep then
    (
        swap coord[1] coord[2]
    )
    setPixels img coord col
)

fn drawLine img start end col =
(
    local steep = (abs (end.y - start.y)) > (abs (end.x - start.x))
	
    if steep then
    (
        swap start.x start.y
        swap end.x end.y
    )
	
    if start.x > end.x then
    (
        swap start.x end.x
        swap start.y end.y
    )
	
    local deltaX = end.x - start.x
    local deltaY = abs (end.y - start.y)
    local error = deltaX / 2.0
    local yStep = -1
    local y = start.y
	
    if start.y < end.y then
    (
        yStep = 1
    )
	
    for x in start.x to end.x do
    (
        plot img [x, y] steep col
        error -= deltaY
        if error < 0 then
        (
            y += yStep
            error += deltaX
        )
    )
    img
)

myBitmap = bitmap 512 512 color:(color 0 0 0)
myBitmap = drawLine myBitmap [0, 511] [511, 0] #((color 255 255 255))
display myBitmap

OCaml

<ocaml>let draw_line ~img ~color ~p0:(x0,y0) ~p1:(x1,y1) =

 let steep = abs(y1 - y0) > abs(x1 - x0) in

 let plot =
   if steep
   then (fun x y -> put_pixel img color y x)
   else (fun x y -> put_pixel img color x y)
 in

 let x0, y0, x1, y1 =
   if steep
   then y0, x0, y1, x1
   else x0, y0, x1, y1
 in
 let x0, x1, y0, y1 =
   if x0 > x1
   then x1, x0, y1, y0
   else x0, x1, y0, y1
 in

 let delta_x = x1 - x0
 and delta_y = abs(y1 - y0) in
 let error = -delta_x / 2
 and y_step =
   if y0 < y1 then 1 else -1
 in
 let rec loop x y error =
   plot x y;
   if x <= x1 then
     let error = error + delta_y in
     let y, error =
       if error > 0
       then (y + y_step), (error - delta_x)
       else y, error
     in
     loop (succ x) y error
 in
 loop x0 y0 error

</ocaml>