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https://git.sr.ht/~rabbits/macintosh_cookbook
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78 lines
1.6 KiB
ObjectPascal
78 lines
1.6 KiB
ObjectPascal
program ExampleBresenham;
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{Program to draw a straight }
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{ line from (x1,y1) to (x2,y2) }
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{using Bresenham's Algorithm }
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var
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i, irange, xp, yp, dxs, dys: Integer;
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x1, y1, x2, y2: Real;
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dx, dy, x, y, range: Real;
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errp: Real;
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axis: char;
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procedure point (x, y: integer);
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{Procedure to plot point at (x,y)}
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begin
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Moveto(xp, yp);
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Lineto(xp, yp);
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end;
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begin
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{Query the user for two points}
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Writeln('Bresenham''s Straight-Line Algorithm');
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Writeln('Input point 1 (x1,y1):');
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Readln(x1, y1);
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Writeln('Input point 2 (x2,y2):');
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Readln(x2, y2);
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range := abs(x2 - x1);
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axis := 'x';
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{Test for axis of more rapid motion}
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if abs(y2 - y1) > range then
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begin
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range := abs(y2 - y1);
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axis := 'y';
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end;
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irange := round(range);
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dx := (x2 - x1);
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dy := (y2 - y1);
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errp := 2 * dy - dx;
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dxs := 1;
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{Test for direction of x motion}
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if dx < 0 then
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dxs := -1;
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dys := 1;
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{Test for direction of y motion}
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if dy < 0 then
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dys := -1;
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xp := round(x1);
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yp := round(y1);
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ShowDrawing;
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{This part steps along x axis}
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case axis of
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'x':
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begin
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for i := 1 to irange do
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begin
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point(xp, yp);
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if errp > 0 then
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begin
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yp := yp + dys;
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errp := errp - 2 * dx * dxs
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end;
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xp := xp + dxs;
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errp := errp + 2 * dy * dys;
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end;
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end;
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'y': {This part steps along y axis}
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begin
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for i := 1 to irange do
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begin
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point(xp, yp);
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if errp > 0 then
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begin
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xp := xp + dxs;
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errp := errp - 2 * dy * dys
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end;
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yp := yp + dys;
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errp := errp + 2 * dx * dxs;
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end;
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end;
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end;
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end. |