二次插值样条曲线

版权声明：欢迎转载，请注明出处噢，谢谢 https://blog.csdn.net/DT2131/article/details/78948132

二次插值样条曲线补首尾的画法

N 为点数+2，虚拟首尾

DIV 代表曲线细分的程度

使用了 EasyX 图形库，感谢 EasyX 团队

#include <bits/stdc++.h>
#include <graphics.h>
#include <conio.h>
using namespace std;
typedef struct Node {
	int x, y;
}Node;
const int N = 8 + 2;
const int DIV = 50000;
Node nodes[N];
void input() {
	nodes[1] = { 100,100 };
	nodes[2] = { 140,160 };
	nodes[3] = { 180,200 };
	nodes[4] = { 220,220 };
	nodes[5] = { 260,270 };
	nodes[6] = { 300,300 };
	nodes[7] = { 340,320 };
	nodes[8] = { 370,370 };
	nodes[0] = nodes[1];
	nodes[9] = nodes[8];
	for (int i = 0; i < N; i++)
		putpixel(nodes[i].x, nodes[i].y, RED);
}
void interpolation() {
	int x, y;
	double t, dt = 0.5 / DIV;
	for (int i = 0; i < N - 3; i++) {
		for (t = 0; t <= 0.5; t += dt) {
			x = (-4 * t*t*t + 4 * t*t - t)*nodes[i].x + (12 * t*t*t - 10 * t*t + 1)*nodes[i + 1].x + (-12 * t*t*t + 8 * t*t + t)*nodes[i + 2].x + (4 * t*t*t - 2 * t*t)*nodes[i + 3].x;
			y = (-4 * t*t*t + 4 * t*t - t)*nodes[i].y + (12 * t*t*t - 10 * t*t + 1)*nodes[i + 1].y + (-12 * t*t*t + 8 * t*t + t)*nodes[i + 2].y + (4 * t*t*t - 2 * t*t)*nodes[i + 3].y;
			putpixel(x, y, WHITE);
		}
	}
}
int main()
{
	initgraph(640, 480);
	input();
	interpolation();
	system("pause");
    return 0;
}