Initial data commit

Task/Bitmap-Bresenhams-line-algorithm/Prolog/bitmap-bresenhams-line-algorithm.pro

@@ -0,0 +1,36 @@
+:- use_module(bitmap).
+:- use_module(bitmapIO).
+:- use_module(library(clpfd)).
+
+% ends when X1 = X2 and Y1 = Y2
+draw_recursive_line(NPict,Pict,Color,X,X,_DX,_DY,Y,Y,_E,_Sx,_Sy):-
+	set_pixel0(NPict,Pict,[X,Y],Color).
+draw_recursive_line(NPict,Pict,Color,X,X2,DX,DY,Y,Y2,E,Sx,Sy):-
+	set_pixel0(TPict,Pict,[X,Y],Color),
+	E2 #= 2*E,
+	% because we can't accumulate error we set Ey or Ex to 1 or 0
+	% depending on whether we need to add dY or dX to the error term
+	(   E2 >= DY ->
+	        Ey = 1, NX #= X + Sx;
+	        Ey = 0, NX = X),
+	(   E2 =< DX ->
+	        Ex = 1, NY #= Y + Sy;
+		Ex = 0, NY = Y),
+	NE #= E + DX*Ex + DY*Ey,
+	draw_recursive_line(NPict,TPict,Color,NX,X2,DX,DY,NY,Y2,NE,Sx,Sy).
+
+draw_line(NPict,Pict,Color,X1,Y1,X2,Y2):-
+	DeltaY #= Y2-Y1,
+	DeltaX #= X2-X1,
+	(   DeltaY < 0 -> Sy = -1; Sy = 1),
+	(   DeltaX < 0 -> Sx = -1; Sx = 1),
+	DX #= abs(DeltaX),
+	DY #= -1*abs(DeltaY),
+	E #= DY+DX,
+	draw_recursive_line(NPict,Pict,Color,X1,X2,DX,DY,Y1,Y2,E,Sx,Sy).
+
+
+ init:-
+	new_bitmap(B,[100,100],[255,255,255]),
+	draw_line(NB,B,[0,0,0],2,2,10,90),
+	write_ppm_p6('line.ppm',NB).