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Xiaolin Wu's line algorithm: Difference between revisions
→{{header|Pascal}}
(→{{header|J}}: use isidraw in j802) |
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Line 591:
const
FPS = 1000 div 60;
SCALE = 6;
var
Line 600:
origin: TSDL_Point;
event: TSDL_Event;
line_alpha: byte = 255;
procedure SDL_RenderDrawWuLine(renderer: PSDL_Renderer; x1, y1, x2, y2: longint);
Line 613:
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^);
Line 653:
SDL_SetRenderDrawColor(renderer, r, g, b, a_new);
SDL_RenderDrawPoint(renderer, px^, py^);
iy := iy + gradient;
end;
SDL_SetRenderDrawColor(renderer, r, g, b, a);
Line 660:
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);
Line 672:
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;
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