// 程序：畫貝塞爾曲線的函數(shù)
// 編譯環(huán)境：Visual Studio 2019，EasyX_20211109
//
 
 
#include <graphics.h>
#include <conio.h>
using namespace std;
 
// 畫貝塞爾曲線的函數(shù)，包括這個 Vec2 結(jié)構(gòu)體
struct Vec2
{
	double x, y;
};
void drawBezierCurve(COLORREF color, const unsigned int len, ...)
{
	if (len <= 0) return;
 
	va_list list;
	va_start(list, len);
	Vec2* temp = new Vec2[len];
	for (int i = 0; i < len; i++)
		temp[i] = va_arg(list, Vec2);
	va_end(list);
 
	if (len == 1)
	{
		putpixel(temp->x, temp->y, color);
		return;
	}
 
	Vec2* parent = nullptr, * child = nullptr;
	Vec2 lastPoint = temp[0];
	setlinecolor(color);
	for (double LineNum = 0; LineNum < 1 + 1.0 / 100; LineNum += 1.0 / 100)
	{
		int size = len;
		parent = temp;
		while (size > 1)
		{
			child = new Vec2[size - 1];
			for (int i = 0; i < size - 1; i++)
			{
				child[i].x = parent[i].x + (parent[i + 1].x - parent[i].x) * LineNum;
				child[i].y = parent[i].y + (parent[i + 1].y - parent[i].y) * LineNum;
			}
			if (parent != temp)delete[] parent;
			parent = child;
			size--;
		}
		line(lastPoint.x, lastPoint.y, parent->x, parent->y);
		lastPoint.x = parent->x;
		lastPoint.y = parent->y;
		delete[] parent;
		parent = nullptr;
		child = nullptr;
	}
	delete[] temp;
}
 
int main()
{
	initgraph(640, 480);
 
	Vec2 a = { 100, 80 };
	Vec2 b = { 540, 80 };
	Vec2 c = { 540, 400 };
	Vec2 d = { 100, 400 };
 
	setlinecolor(BLUE);
	line(a.x, a.y, b.x, b.y);
	line(b.x, b.y, c.x, c.y);
	line(c.x, c.y, d.x, d.y);
 
	drawBezierCurve(RED, 4, a, b, c, d);
 
	_getch();
	closegraph();
	return 0;
}