Bitmap/Bresenham's line algorithm: Difference between revisions
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Using the data storage type defined [[Basic_bitmap_storage|on this page]] for raster graphics images, draw a line given 2 points with the Bresenham's algorithm ([http://en.wikipedia.org/wiki/Bresenham's_line_algorithm definition on Wikipedia]).
=={{header|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
<pre>
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
</pre>
=={{header|C}}==
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#undef swap_uint
#undef plot</C>
=={{header|MAXScript}}==
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