Xiaolin Wu's line algorithm: Difference between revisions
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End Function
</lang>
=={{header|Pascal}}==
{{works with|Free Pascal}}
{{libheader|SDL2}}
Based on Wikipwdia pseudocode with some optimizations and alpha handling.
<lang pascal>
program wu;
uses
SDL2,
math;
const
FPS=1000 div 60;
SCALE=6;
var
win: PSDL_Window;
ren: PSDL_Renderer;
mouse_x, mouse_y: longint;
origin: TSDL_Point;
event: TSDL_Event;
line_alpha: byte=255;
procedure SDL_RenderDrawWuLine(renderer: PSDL_Renderer; x1, y1, x2, y2: longint);
var
r, g, b, a, a_new: Uint8;
gradient, iy: real;
x, y: longint;
px, py: plongint;
procedure swap(var a, b: longint);
var
tmp: longint;
begin
tmp:=a;
a:=b;
b:=tmp;
end;
begin
if a=0 then
exit;
SDL_GetRenderDrawColor(renderer, @r, @g, @b, @a);
if abs(y2-y1)>abs(x2-x1) then
begin
swap(x1, y1);
swap(x2, y2);
px:=@y;
py:=@x;
end
else
begin
px:=@x;
py:=@y;
end;
if x1>x2 then
begin
swap(x1, x2);
swap(y1, y2);
end;
x:=x2-x1;
if x=0 then
x:=1;
gradient:=(y2-y1)/x;
iy:=y1;
for x:=x1 to x2 do
begin
a_new:=round(a*frac(iy));
y:=floor(iy);
SDL_SetRenderDrawColor(renderer, r, g, b, a-a_new);
SDL_RenderDrawPoint(renderer, px^, py^);
inc(y);
SDL_SetRenderDrawColor(renderer, r, g, b, a_new);
SDL_RenderDrawPoint(renderer, px^, py^);
iy:=iy+gradient;
end;
SDL_SetRenderDrawColor(renderer, r, g, b, a);
end;
begin
SDL_Init(SDL_INIT_VIDEO);
win:=SDL_CreateWindow('Xiaolin Wu''s line algorithm', SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
640, 480, SDL_WINDOW_RESIZABLE);
ren:=SDL_CreateRenderer(win, -1, 0);
if ren=NIL then
begin
writeln(SDL_GetError);
halt;
end;
SDL_SetRenderDrawBlendMode(ren, SDL_BLENDMODE_BLEND);
SDL_RenderSetScale(ren, SCALE, SCALE);
SDL_SetCursor(SDL_CreateSystemCursor(SDL_SYSTEM_CURSOR_CROSSHAIR));
mouse_x:=0;
mouse_y:=0;
origin.x:=0;
origin.y:=0;
repeat
while SDL_PollEvent(@event)=1 do
case event.type_ of
SDL_KEYDOWN:
if event.key.keysym.sym=SDLK_ESCAPE then
halt;
SDL_MOUSEBUTTONDOWN:
begin
origin.x:=mouse_x;
origin.y:=mouse_y;
end;
SDL_MOUSEMOTION:
with event.motion do
begin
mouse_x:=x div SCALE;
mouse_y:=y div SCALE;
end;
SDL_MOUSEWHEEL:
line_alpha:=EnsureRange(line_alpha+event.wheel.y*20, 0, 255);
SDL_QUITEV:
halt;
end;
SDL_SetRenderDrawColor(ren, 35, 35, 35, line_alpha);
SDL_RenderDrawWuLine(ren, origin.x, origin.y, mouse_x, mouse_y);
SDL_RenderPresent(ren);
SDL_SetRenderDrawColor(ren, 255, 255, 255, 255);
SDL_RenderClear(ren);
SDL_Delay(FPS);
until false;
end.
</lang>
=={{header|Perl}}==
This is mostly a translation of the pseudo-code on Wikipedia, except that the $plot trick was inspired by the perl6 RosettaCode example.
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