一个可以生成贝塞尔曲线的小程序

-- 这是代码，写得比较随意，不是很好。
IDLE = 0
DRAW_START = 1
DRAW_MOVING = 2
DRAW_END = 3
EDIT = 4
function setup()
print("三阶贝塞尔曲线")
print("拖动创建线条")
print("移动控制点调整曲线")
controlPoints = {}
size = 35 -- 控制点大小
status = IDLE
selected = nil
end
function draw()
background(255)
if status == DRAW_START then
status = IDLE
sp = touchPos
elseif status == DRAW_MOVING then
styleLine(sp,touchPos,color(0, 75),8)
elseif status == DRAW_END then
ep = touchPos
cp = CP(sp,ep) -- 计算控制点
table.insert(controlPoints,{p0 = sp,p1 = ep,cp1 = cp[1],cp2 = cp[2],b={}})
for i = 0,1,0.05 do
local cpoint = controlPoints[#controlPoints]
table.insert(cpoint.b,calculatebezier(i,cpoint.p0,cpoint.p1,cpoint.cp1,cpoint.cp2))
end
status = IDLE
end
if selected ~= nil then
if selected.y == 1 then
controlPoints[selected.x].cp1 = touchPos
elseif selected.y == 2 then
controlPoints[selected.x].cp2 = touchPos
elseif selected.y == 3 then
controlPoints[selected.x].p0 = touchPos
elseif selected.y == 4 then
controlPoints[selected.x].p1 = touchPos
end
end
for k,v in pairs(controlPoints) do
for i = 1,#v.b - 1 do
for t = 0,20 do
v.b[t+1] = calculatebezier(t/20,v.p0,v.p1,v.cp1,v.cp2)
end
styleLine(v.b[i],v.b[i + 1],color(0),8)
end
styleLine(v.p0,v.cp1,color(129, 65),8)
styleLine(v.p1,v.cp2,color(129, 65),8)
drawPoints(v,color(255),size)
end
end

function touched(touch)
touchPos = vec2(touch.x,touch.y)
if status ~= EDIT then
if touch.state == BEGAN then
status = DRAW_START
elseif touch.state == MOVING then
status = DRAW_MOVING
else
status = DRAW_END
end
end
for k,v in ipairs(controlPoints) do
if collide(touchPos,v.cp1,size*2) then
status = EDIT
if touch.state == BEGAN and selected == nil then
selected = vec2(k,1)
end
elseif collide(touchPos,v.cp2,size*2) then
status = EDIT
if touch.state == BEGAN and selected == nil then
selected = vec2(k,2)
end
elseif collide(touchPos,v.p0,size*2) then
status = EDIT
if touch.state == BEGAN and selected == nil then
selected = vec2(k,3)
end
elseif collide(touchPos,v.p1,size*2) then
status = EDIT
if touch.state == BEGAN and selected == nil then
selected = vec2(k,4)
end
end
if touch.state == ENDED and status == EDIT then
selected = nil
status = IDLE
end
end
end

function calculatebezier(t,p0,p1,c0,c1)
local b = p0*(1 - t)^3 + 3*c0*t*(1 - t)^2 + 3*c1*(t^2)*(1 - t) + (t^3)*p1
return b
end
function CP(p0,p1)
local cp1 = (1 - 1 / 3) * p0 + (1 / 3) * p1
local cp2 = (1 - 2 / 3) * p0 + (2 / 3) * p1
return {cp1,cp2}
end
function collide(pos,target,radius)
if pos:dist(target) <= radius / 2 then
return true
end
end
function drawPoints(cList,c,r)
pushMatrix()
pushStyle()
stroke(0)
strokeWidth(5)
fill(c)
ellipse(cList.p0.x,cList.p0.y,r)
ellipse(cList.p1.x,cList.p1.y,r)
rectMode(CENTER)
rect(cList.cp1.x,cList.cp1.y,r,r)
rect(cList.cp2.x,cList.cp2.y,r,r)
popStyle()
popMatrix()
end
function styleLine(pos1,pos2,c,s)
pushMatrix()
pushStyle()
stroke(c)
strokeWidth(s)
line(pos1.x,pos1.y,pos2.x,pos2.y)
popStyle()
popMatrix()
end