#include <graphics.h>
#include <algorithm>
#include <cmath>
#include <stdio.h>
#include <map>

using namespace std;

//判断点v是否在[a,b]中

//C#与JAVa的后遗症，EGEAPP
namespace EA {
	using namespace std;
#define ct color_t
	//几个全局变量
	//屏幕buffer
	color_t* wBuffer=nullptr;
	//纹理buffer
	color_t* tBuffer=nullptr;
	//屏幕长宽
	int W=0;
	int H=0;

	inline float F2I(float f) {
		return floor(f);
	}
	//把浮点数位数强定为3位(担心爆精度
	inline float F2F3(float f) {
		return floor(f*1000.0f)/1000.0f;
	}
	template<class T>
	inline bool IsCovered(T a,T b,T v) {
		if(a>b) swap(a,b);
		return (a<=v&&v<=b);
	}

	//数据类型
	class Vertex2D {
		public:
			float x;
			float y;
			ct c;
			inline Vertex2D() {
				x=y=0.0f;
				c=0;
			}
			inline Vertex2D(float _x,float _y,ct _c) {
				x=_x,y=_y,c=_c;
			}
			inline void Format() {
				x=EA::F2I(x);
				y=EA::F2I(y);
			}
			inline VECTOR3D ToVec3D() {
				return VECTOR3D(x,y,0);
			}
	};
	typedef struct Vertex2D Ver2D;
	//函数
	//初始化绘图环境
	void InitGraph(int w,int h) {
		initgraph(w,h,0);
		ege_enable_aa(1);
		W=getwidth(),H=getheight();
		wBuffer=getbuffer(NULL);
	}
	//颜色插值,0<=v<=1
	inline ct ColorLerp(ct c1,ct c2,float v);
	//2D顶点插值 
	inline Ver2D V2DLerp(Ver2D v1,Ver2D v2,float t); 
	//高速画点
	inline void PutPixel_f(Ver2D v);
	//高速画水平线
	//这个会渐变
	inline void DrawLine_f(float x1,float x2,float y,ct c1,ct c2);
	//绘制简单三角，要求至少两个点y一样
	inline void DrawSimpleTrangle(Ver2D v1,Ver2D v2,Ver2D v3);
	//绘制复杂三角
	inline void DrawTrangle(Ver2D v1,Ver2D v2,Ver2D v3);
#undef ct
}

using EA::Ver2D;

#define ct color_t
//程序入口
int main() {
	EA::InitGraph(1000,600);
	EA::DrawTrangle(Ver2D(0,EA::H/2,RED),Ver2D(EA::W/4,0,GREEN),Ver2D(EA::W/2,EA::H,BLUE));
	delay_fps(60);
	getch();
	closegraph();
	return 0;
}

ct EA::ColorLerp(ct c1,ct c2,float v) {
	v=EA::F2F3(v);
	int r=EGEGET_R(c1)-EGEGET_R(c2);
	int g=EGEGET_G(c1)-EGEGET_G(c2);
	int b=EGEGET_B(c1)-EGEGET_B(c2);
	r=r*v+EGEGET_R(c2);
	g=g*v+EGEGET_G(c2);
	b=b*v+EGEGET_B(c2);
	return EGERGB(r,g,b);
}
void EA::PutPixel_f(Ver2D v) {
	v.Format();
	if(EA::IsCovered(0,W,int(v.x))&&EA::IsCovered(0,H,int(v.y))) {
		wBuffer[int(v.x+v.y*W)]=v.c;
	}
}
void EA::DrawLine_f(float x1,float x2,float y,ct c1,ct c2) {
	if(x1>x2) swap(x1,x2);
	x1=F2I(x1);
	x2=F2I(x2);
	y=F2I(y);
	for(float i=x1; i<=x2; ++i) {
		PutPixel_f(Vertex2D(i,y,ColorLerp(c1,c2,float((i-x1)/(x2-x1)))));
	}
}
//v1.y==v2.y
void EA::DrawSimpleTrangle(Ver2D v1,Ver2D v2,Ver2D v3) {
	//Format
	if(v2.y==v3.y&&v1.y!=v2.y) {
		swap(v1,v2);
		swap(v2,v3);
	} else if(v1.y==v3.y&&v1.y!=v2.y) {
		swap(v2,v3);
	}
	if(v1.x>v2.x) {
		swap(v1,v2);
	}
	//解一次方程
	float h=v3.y-v1.y;
	float kL=(v3.x-v1.x)/h;
	float kR=(v3.x-v2.x)/h;

	float xL=0;
	float xR=0;

	ct c1=0,c2=0;
	xL=v1.x;
	xR=v2.x;
	if(h>0) {
		for(float i=v1.y; i<=v3.y; ++i) {
			float percent=1.0f-(i-v1.y)/(v3.y-v1.y);
			c1=EA::ColorLerp(v1.c,v3.c,percent);
			c2=EA::ColorLerp(v2.c,v3.c,percent);
			EA::DrawLine_f(xL,xR,i,c1,c2);
			xL+=kL;
			xR+=kR;
		}
	} else {
		for(float i=v1.y; i>=v3.y; --i) {
			float percent=(i-v3.y)/(v1.y-v3.y);
			c1=EA::ColorLerp(v1.c,v3.c,percent);
			c2=EA::ColorLerp(v2.c,v3.c,percent);
			EA::DrawLine_f(xL,xR,i,c1,c2);
			xL-=kL;
			xR-=kR;
		}
	}
}
void EA::DrawTrangle(Ver2D v1,Ver2D v2,Ver2D v3) {
	if(v1.y==v2.y||v1.y==v3.y||v2.y==v3.y) {
		EA::DrawSimpleTrangle(v1,v2,v3);
	} else {
		//找出y中间的顶点，并放在v3的位置
		if(v2.y<v1.y&&v1.y<v3.y) {
			swap(v1,v3);
		} else if(v1.y<v2.y&&v2.y<v3.y) {
			swap(v2,v3);
		}
		//切成两半
		float h=v1.y-v2.y;
		float w=v1.x-v2.x;
		Ver2D vm((w/h)*(v3.y-v2.y)+v2.x,v3.y,EA::ColorLerp(v2.c,v1.c,(v3.y-v2.y)/h));
		swap(vm.c,v3.c);
		//画他
		DrawSimpleTrangle(v1,vm,v3);
		DrawSimpleTrangle(v2,vm,v3);
	}
}
#undef ct