37 lines
974 B
Prolog
37 lines
974 B
Prolog
use_module(library(pce)).
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lindraw(X1,Y1,X2,Y2):-
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new(Win,window("Line")),
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new(Pix,pixmap(@nil,black,white,X2+30,Y2+30)),
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send(Win,size,size(400,400)),
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draw_line(Pix,X1,Y1,X2,Y2),
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new(Bmp,bitmap(Pix)),
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send(Win,display,Bmp,point(0,0)),
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send(Win,open).
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draw_recursive_line(_Pict,X,X,_DX,_DY,Y,Y,_D,_Sx,_Sy).%Don't iterate if X and X2 are the same number
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draw_recursive_line(Pict,X,X2,DX,DY,Y,Y2,C,Sx,Sy):-
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( C>0->%If the difference is greater than one, add Y one to Y.
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Y1 is Y+Sy,
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send(Pict,pixel(X,Y1,colour(black))),
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C2 is C+(2*DY-2*DX);
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Y1 is Y,
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send(Pict,pixel(X,Y,colour(black))),
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C2 is C+(2*DY)),
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X0 is X+Sx,%The next iteration
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draw_recursive_line(Pict,X0,X2,DX,DY,Y1,Y2,C2,Sx,Sy).
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isneg(X,O):-
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( X<0->
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O is -1;
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( X\==0->
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O is 1;
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O is 0)).
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draw_line(Pict,X1,Y1,X2,Y2):-
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DY is abs(Y2-Y1),
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DX is abs(X2-X1),
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isneg(DX,Sx),
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isneg(DY,Sy),
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D = 2*DY-DX,%The slope of the line
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draw_recursive_line(Pict,X1,X2,DX,DY,Y1,Y2,D,Sx,Sy).
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