直线段裁剪 Cohen_SutherLand 以及 Liang_Barsky 算法

#include <iostream>#include <cstdlib>#include <ctime>#include <cmath>#include <cstring>#include <vector>#include <algorithm>using namespace std;const int maxX = 1080, maxY = 1920, maxP = 40;const int LineW = 4;const int xMax = 800, xMin = 300, yMax = 1300, yMin = 600;int num[maxX][maxY];const double eps = 1e-6, Pi = 4 * atan(1);struct Point {double x, y;Point(double x = 0, double y = 0) : x(x), y(y) {}};double operator * (Point a, Point b) {return a.x * b.x + a.y * b.y;}Point operator - (Point a, Point b) {return Point(a.x - b.x, a.y - b.y);}double operator ^ (Point a, Point b) {return a.x * b.y - a.y * b.x;}double mod(Point a) {return sqrt(a * a * 1.0);}double theta(Point a, Point b) {double csin = (a ^ b) / mod(a) / mod(b);double ccos = (a * b) / mod(a) / mod(b);return atan2(csin, ccos);}void Cohen_SutherLand(Point& a, Point& b) {int aOrder = 0, bOrder = 0;if (a.x < xMin)aOrder |= (1 << 0);if (a.x > xMax)aOrder |= (1 << 1);if (a.y < yMin)aOrder |= (1 << 2);if (a.y > yMax)aOrder |= (1 << 3);if (b.x < xMin)bOrder |= (1 << 0);if (b.x > xMax)bOrder |= (1 << 1);if (b.y < yMin)bOrder |= (1 << 2);if (b.y > yMax)bOrder |= (1 << 3);if ((aOrder & bOrder) != 0) {a = Point(-1, -1);b = Point(-1, -1);return;}if ((aOrder | bOrder) == 0)return;if (aOrder != 0) {if ((aOrder & (1 << 0)) != 0) {a.y = a.y + (b.y - a.y) / (b.x - a.x) * (xMin - a.x);a.x = xMin;Cohen_SutherLand(a, b);}else if ((aOrder & (1 << 1)) != 0) {a.y = a.y + (b.y - a.y) / (b.x - a.x) * (xMax - a.x);a.x = xMax;Cohen_SutherLand(a, b);}else if ((aOrder & (1 << 2)) != 0) {a.x = a.x + (b.x - a.x) / (b.y - a.y) * (yMin - a.y);a.y = yMin;Cohen_SutherLand(a, b);}else if ((aOrder & (1 << 3)) != 0) {a.x = a.x + (b.x - a.x) / (b.y - a.y) * (yMax - a.y);a.y = yMax;Cohen_SutherLand(a, b);}}else if (bOrder != 0) {if ((bOrder & (1 << 0)) != 0) {b.y = b.y + (a.y - b.y) / (a.x - b.x) * (xMin - b.x);b.x = xMin;Cohen_SutherLand(a, b);}else if ((bOrder & (1 << 1)) != 0) {b.y = b.y + (a.y - b.y) / (a.x - b.x) * (xMax - b.x);b.x = xMax;Cohen_SutherLand(a, b);}else if ((bOrder & (1 << 2)) != 0) {b.x = b.x + (a.x - b.x) / (a.y - b.y) * (yMin - b.y);b.y = yMin;Cohen_SutherLand(a, b);}else if ((bOrder & (1 << 3)) != 0) {b.x = b.x + (a.x - b.x) / (a.y - b.y) * (yMax - b.y);b.y = yMax;Cohen_SutherLand(a, b);}}return;}void LiangYoudong_Barsky(Point& a, Point& b) {double t_xMin = (xMin - a.x) / (b.x - a.x),       t_xMax = (xMax - a.x) / (b.x - a.x),       t_yMin = (yMin - a.y) / (b.y - a.y),       t_yMax = (yMax - a.y) / (b.y - a.y);if (t_yMin > t_yMax)swap(t_yMin, t_yMax);if (t_xMin > t_xMax)swap(t_xMin, t_xMax);double t_Begin = max(0.0, max(t_xMin, t_yMin)),       t_End = min(1.0, min(t_xMax, t_yMax));if (t_Begin >= t_End) {a = Point(-1, -1);b = Point(-1, -1);}else {Point aTemp = a, bTemp = b;a.x = aTemp.x + t_Begin * (bTemp.x - aTemp.x);a.y = aTemp.y + t_Begin * (bTemp.y - aTemp.y);b.x = aTemp.x + t_End * (bTemp.x - aTemp.x);b.y = aTemp.y + t_End * (bTemp.y - aTemp.y);}return;}const int val[5][5] = {1, 2, 4, 2, 1,2, 5, 6, 5, 2,4, 6, 8, 6, 4,2, 5, 6, 5, 2,1, 2, 4, 2, 1,}, SUM = 88;Point p[maxP];void naiveFill() {freopen("test_n.pgm", "w", stdout);cout << "P2" << endl;cout << maxY << " " << maxX << endl;cout << "255" << endl;for (int i = 0; i < maxX; i++, (cerr << i << endl))for (int j = 0; j < maxY; j++) {int res = 0;for (int k = 0; k < 5; k++)for (int l = 0; l < 5; l++) {Point temp(i + 0.1 + 0.2 * k, j + 0.1 + 0.2 * l);double the = 0;for (int m = 0; m < maxP; m++)the += theta(p[m] - temp, p[(m + 1) % maxP] - temp);if (fabs(fabs(the) - 2 * Pi) <= eps)res += val[k][l];}num[i][j] = 255 * res / SUM;}for (int i = 0; i < maxX; i++)for (int j = 0; j < maxY; j++)cout << num[i][j] << " ";}bool inBlock[maxX * 5][maxY * 5];struct Edge {double xCurr, yMin, yMax, delta = 0;bool alive = true;} edge[2 * maxP];bool operator < (const Edge& a, const Edge& b) {return a.xCurr < b.xCurr;}void scanningLineFill() {freopen("test_s.pgm", "w", stdout);cout << "P2" << endl;cout << maxY << " " << maxX << endl;cout << "255" << endl;for (int i =  0; i < maxP; i++) {Point a = p[i], b = p[(i + 1) % maxP];Cohen_SutherLand(a, b);//LiangYoudong_Barsky(a, b);if (a.y > b.y)swap(a, b);edge[2 * i].yMin = a.y;edge[2 * i].yMax = b.y;edge[2 * i].xCurr = a.x;if (a.y != b.y) edge[2 * i].delta = (b.x - a.x) / (b.y - a.y);elseedge[2 * i].alive = false;edge[2 * i + 1].yMin = a.y;edge[2 * i + 1].yMax = b.y;edge[2 * i + 1].xCurr = a.x + LineW;if (a.y != b.y) edge[2 * i + 1].delta = (b.x - a.x) / (b.y - a.y);elseedge[2 * i + 1].alive = false;}sort(edge, edge + 2 * maxP, [] (Edge a, Edge b) {return a.yMin < b.yMin;});vector<Edge> aliveEdge;int edgeCurr = 0;for (int i = 0; i < maxY; i++) for (int k = 0; k < 5; k++) {double yCurr = i + 0.1 + k * 0.2;if (k == 0)for (int j = 0; j < aliveEdge.size(); j++)if (aliveEdge[j].yMax <= i)aliveEdge[j].alive = false;for (int j = 0; j < aliveEdge.size(); j++)aliveEdge[j].xCurr += 0.2 * aliveEdge[j].delta;while (edgeCurr < 2 * maxP && edge[edgeCurr].yMin <= yCurr) {Edge tempEdge = edge[edgeCurr];tempEdge.xCurr += (yCurr - edge[edgeCurr++].yMin) * tempEdge.delta;aliveEdge.push_back(tempEdge);}sort(aliveEdge.begin(), aliveEdge.end());int pointCurr = 0, inLine = 0;for (int j = 0; j < maxX; j++)for (int l = 0; l < 5; l++) {double xCurr = j + 0.1 + l * 0.2;while (pointCurr < aliveEdge.size() && aliveEdge[pointCurr].xCurr < xCurr)if (aliveEdge[pointCurr++].alive == true)inLine ^= 1;inBlock[j * 5 + l][i * 5 + k] = inLine;}}for (int i = 0; i < maxX; i++)for (int j = 0; j < maxY; j++) {int nCurr = 0;for (int k = 0; k < 5; k++)for (int l = 0; l < 5; l++)if (inBlock[i * 5 + k][j * 5 + l])nCurr += val[k][l];num[i][j] = 255 * nCurr / SUM;}for (int i = 0; i < maxX; i++)for (int j = 0; j < maxY; j++)cout << num[i][j] << " ";}int main() {//srand(time(NULL));for (int i = 0; i < maxP; i++) {int x = rand() % maxX, y = rand() % maxY;p[i] = Point(x, y);}scanningLineFill();//naiveFill();return 0;}