花了两个小时把这个东西做好了。虽然不及[LIEN87 ; SHAN87 ; SHAN89]论文厉害，不过自己弄的这个写起来倒是相当容易的。在这里贴出效果图和代码。效果图中，我先使用蓝色画笔，用PolyBezier绘制曲线，然后使用红色像素使用自己的算法绘制曲线。可以看见有一点点误差，不过效果还是可以接受的。代码仍然使用自己的那套库开发，不过曲线扫描的方法不受库的限制。这个算法保证非交叉部分的点不会被重复绘制。
有了这个算法之后我就可以把贝塞尔曲线转换成密度刚好的折线了。这才是最终目的。
1 #include "..\..\..\..\Library\Windows\VL_WinMain.h"
2 #include "..\..\..\..\Library\Windows\VL_WinGDI.h"
3
4 using namespace vl;
5 using namespace vl::windows;
6
7 class MyForm : public VL_WinForm
8 {
9 protected:
10 VL_WinDIB* FBuffer;
11 VL_WinDC* FBufferDC;
12 VL_WinDC* FFormDC;
13 VL_WinPen::Ptr FGDIPen;
14 VL_WinPen::Ptr FMyPen;
15
16 POINT FControlPoints[4];
17 VInt FMouseIndex;
18
19 void Clear()
20 {
21 FBufferDC->FillRect(0,0,800,600);
22 }
23
24 void GetD(VDouble T , VDouble& dX , VDouble& dY)
25 {
26 dX= FControlPoints[0].x*(-3*(1-T)*(1-T))+
27 FControlPoints[1].x*(-6*T*(1-T)+3*(1-T)*(1-T))+
28 FControlPoints[2].x*(-3*T*T+6*T*(1-T))+
29 FControlPoints[3].x*3*T*T;
30
31 dY= FControlPoints[0].y*(-3*(1-T)*(1-T))+
32 FControlPoints[1].y*(-6*T*(1-T)+3*(1-T)*(1-T))+
33 FControlPoints[2].y*(-3*T*T+6*T*(1-T))+
34 FControlPoints[3].y*3*T*T;
35 }
36
37 void GetP(VDouble T , VDouble& X , VDouble& Y)
38 {
39 X= FControlPoints[0].x*(1-T)*(1-T)*(1-T)+
40 FControlPoints[1].x*3*T*(1-T)*(1-T)+
41 FControlPoints[2].x*3*T*T*(1-T)+
42 FControlPoints[3].x*T*T*T;
43
44 Y= FControlPoints[0].y*(1-T)*(1-T)*(1-T)+
45 FControlPoints[1].y*3*T*(1-T)*(1-T)+
46 FControlPoints[2].y*3*T*T*(1-T)+
47 FControlPoints[3].y*T*T*T;
48 }
49
50 void SetColor(VInt X , VInt Y , VInt Color)
51 {
52 VByte R=Color%256;
53 VByte G=(Color>>8)%256;
54 VByte B=(Color>>16)%256;
55 if(X>=0 && X<FBuffer->GetWidth() && Y>=0 && Y<FBuffer->GetHeight())
56 {
57 ((VInt32u*)(FBuffer->ScanLines[Y]))[X]=(R<<16)+(G<<8)+B;
58 }
59 }
60
61 void DrawCurve()
62 {
63 FBufferDC->MoveTo(FControlPoints[0].x,FControlPoints[0].y);
64 VDouble T=0.0001;
65 VBool Finished=false;
66 VDouble OldX=FControlPoints[0].x;
67 VDouble OldY=FControlPoints[0].y;
68 VDouble X1,Y1;
69 VDouble X2=FControlPoints[3].x;
70 VDouble Y2=FControlPoints[3].y;
71
72 VInt OldX1=FControlPoints[0].x;
73 VInt OldY1=FControlPoints[0].y;
74 VInt OldX2=0;
75 VInt OldY2=0;
76 VBool Old2Available=false;
77 SetColor(OldX1,OldY1,RGB(255,0,0));
78 while(!Finished)
79 {
80 /*初始步长为当前t到结束点*/
81 VDouble dT=(1-T);
82 VBool AtTail=true;
83 while(true)
84 {
85 /*取半步，检查目标点与当前点的长度*/
86 VDouble dTHalf=dT/2;
87 if(dTHalf<0.00001)
88 {
89 dTHalf=dTHalf;
90 }
91 GetP(T+dT,X1,Y1);
92 GetP(T+dTHalf,X2,Y2);
93 VDouble Length=sqrt((X1-OldX)*(X1-OldX)+(Y1-OldY)*(Y1-OldY));
94 VDouble LengthHalf=sqrt((X2-OldX)*(X2-OldX)+(Y2-OldY)*(Y2-OldY));
95 /*如果半步长大于一步则取半步，继续迭代*/
96 if(LengthHalf>=Length)
97 {
98 dT=dTHalf;
99 }
100 else
101 {
102 /*否则，如果全步长产生的距离<=1则绘制*/
103 if(Length<=1)
104 {
105 if(AtTail)
106 {
107 Finished=true;
108 }
109 break;
110 }
111 /*否则进行近似测量*/
112 else
113 {
114 dT*=1/Length;
115 GetP(T+dT,X1,Y1);
116 }
117 }
118 AtTail=false;
119 }
120 /*计算像素位置*/
121 VInt X=Round(X1);
122 VInt Y=Round(Y1);
123 VInt dX_I=(OldX1-X)*(OldX1-X);
124 VInt dY_I=(OldY1-Y)*(OldY1-Y);
125 /*让线条长度保持1*/
126 if(Old2Available)
127 {
128 if(dX_I==1 && dY_I==1)
129 {
130 OldX1=X;
131 OldY1=Y;
132 SetColor(OldX1,OldY1,RGB(255,0,0));
133 }
134 else
135 {
136 OldX1=X;
137 OldY1=Y;
138 SetColor(OldX1,OldY1,RGB(255,0,0));
139 SetColor(OldX2,OldY2,RGB(255,0,0));
140 }
141 Old2Available=false;
142 }
143 else
144 {
145 if(dX_I==1 && dY_I==1)
146 {
147 OldX1=X;
148 OldY1=Y;
149 SetColor(OldX1,OldY1,RGB(255,0,0));
150 }
151 else if(dX_I==1 || dY_I==1)
152 {
153 OldX2=X;
154 OldY2=Y;
155 Old2Available=true;
156 }
157 }
158 OldX=X1;
159 OldY=Y1;
160 T+=dT;
161 }
162 if(Old2Available)
163 {
164 SetColor(OldX2,OldY2,RGB(255,0,0));
165 }
166 }
167
168 void DrawHandles()
169 {
170 for(VInt i=0;i<4;i++)
171 {
172 POINT P=FControlPoints[i];
173 FBufferDC->Ellipse(P.x-2,P.y-2,P.x+2,P.y+2);
174 }
175 }
176
177 void Draw()
178 {
179 Clear();
180 FBufferDC->SetPen(FGDIPen);
181 FBufferDC->PolyBezier(FControlPoints,4);
182 FBufferDC->SetPen(FMyPen);
183 DrawCurve();
184 DrawHandles();
185 FFormDC->Draw(0,0,FBuffer);
186 }
187 public:
188 MyForm():VL_WinForm(true)
189 {
190 FBuffer=new VL_WinDIB(800,600);
191 FBufferDC=&FBuffer->DC;
192 FBufferDC->SetBackTransparent(true);
193 FFormDC=new VL_WinControlDC(GetHandle());
194 FGDIPen=new VL_WinPen(PS_SOLID,1,RGB(0,0,255));
195 FMyPen=new VL_WinPen(PS_SOLID,1,RGB(255,0,0));
196 FMouseIndex=-1;
197
198 FControlPoints[0].x=200;
199 FControlPoints[0].y=400;
200 FControlPoints[1].x=200;
201 FControlPoints[1].y=200;
202 FControlPoints[2].x=400;
203 FControlPoints[2].y=200;
204 FControlPoints[3].x=400;
205 FControlPoints[3].y=400;
206
207 OnPaint.Bind(this,&MyForm::Form_OnPaint);
208 OnLeftButtonDown.Bind(this,&MyForm::Form_OnMouseDown);
209 OnMouseMove.Bind(this,&MyForm::Form_OnMouseMove);
210 OnLeftButtonUp.Bind(this,&MyForm::Form_OnMouseUp);
211
212 SetMaximizeBox(false);
213 SetMinimizeBox(false);
214 SetBorder(vwfbSingle);
215 SetClientWidth(800);
216 SetClientHeight(600);
217 SetText(L"Vczh Bezier");
218 MoveCenter();
219 Draw();
220 Show();
221 }
222
223 ~MyForm()
224 {
225 delete FFormDC;
226 delete FBuffer;
227 }
228
229 void Form_OnPaint(VL_Base* Sender)
230 {
231 FFormDC->Draw(0,0,FBuffer);
232 }
233
234 void Form_OnMouseDown(VL_Base* Sender,VLS_MouseStruct MouseStruct)
235 {
236 /*计算出在鼠标控制范围内（6像素）的控制点*/
237 for(VInt i=0;i<4;i++)
238 {
239 POINT P=FControlPoints[i];
240 if((P.x-MouseStruct.X)*(P.x-MouseStruct.X)+(P.y-MouseStruct.Y)*(P.y-MouseStruct.Y)<=36)
241 {
242 FMouseIndex=i;
243 break;
244 }
245 }
246 Form_OnMouseMove(Sender,MouseStruct);
247 }
248
249 void Form_OnMouseMove(VL_Base* Sender,VLS_MouseStruct MouseStruct)
250 {
251 /*抓住有效控制点的话则移动*/
252 if(FMouseIndex!=-1)
253 {
254 FControlPoints[FMouseIndex].x=MouseStruct.X;
255 FControlPoints[FMouseIndex].y=MouseStruct.Y;
256 Draw();
257 }
258 }
259
260 void Form_OnMouseUp(VL_Base* Sender,VLS_MouseStruct MouseStruct)
261 {
262 /*接触控制*/
263 FMouseIndex=-1;
264 }
265 };
266
267 void main()
268 {
269 new MyForm();
270 GetApplication()->Run();
271 }
posted on 2008-06-11 21:20
陈梓瀚(vczh) 阅读(2615)
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