Bitmap/Bresenham's line algorithm: Difference between revisions
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</lang>
=={{header|Prolog}}==
Works with SWI-prolog.
<lang Prolog>
use_module(library(pce)).
lindraw(X1,Y1,X2,Y2):-
new(Win,window("Line")),
new(Pix,pixmap(@nil,black,white,X2+30,Y2+30)),
send(Win,size,size(400,400)),
drwlin(Pix,X1,Y1,X2,Y2),
new(Bmp,bitmap(Pix)),
send(Win,display,Bmp,point(0,0)),
send(Win,open).
draw_recursive_line(_Pict,X,X,_DX,_DY,_Y,_D).%Don't iterate if X and X2 are the same number
draw_recursive_line(Pict,X,X2,DX,DY,Y,C):-
( C>0->%If the difference is greater than one, add Y one to Y.
Y1 is Y+1,
send(Pict,pixel(X,Y1,colour(black))),
C2 is C+(2*DY-2*DX);
Y1 is Y,
send(Pict,pixel(X,Y,colour(black))),
C2 is C+(2*DY)),
X0 is X+1,%The next iteration
draw_recursive_line(Pict,X0,X2,DX,DY,Y1,C2).
draw_line(Pict,X1,Y1,X2,Y2):-
DY is Y2-Y1,
DX is X2-X1,
D = 2*DY-DX,%The slope of the line
draw_recursive_line(Pict,X1,X2,DX,DY,Y1,D).
</lang>
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