计算机图形学（二）输出图元_20_章节总结_程序展示_饼图

饼图用来给出整体中各部分的分布比例。使用中点圆算法子程序来构造一个饼图。例子中的值用于确定扇形的数量和大小，

该程序的输出请参见图。

#include "stdafx.h"#include "GL/glut.h"#include "stdlib.h"#include "math.h"#include "iostream"using namespace std;const GLdouble twoPi = 6.283185;GLsizei winWidth = 400, winHeight = 300; // Initial display window size.class screenPt {public:screenPt(){x = y = 0;}GLint x, y;void setCoords(GLint xCoordValue, GLint yCorrdValue){x = xCoordValue;y = yCorrdValue;}GLint getx() const{return x;}GLint gety() const{return y;}void incrementx(){x++;}void incrementy(){y--;}};void init( ){glClearColor(1.0, 1.0, 1.0, 1.0);glMatrixMode(GL_PROJECTION);gluOrtho2D(0.0, 200.0, 0.0, 150.0);}void setPixel(GLint xCoord, GLint yCoord){glBegin(GL_POINTS);glVertex2i(xCoord, yCoord);glEnd();}void circleMidpoint(GLint xc, GLint yc, GLint radius){screenPt circPt;GLint p = 1 - radius;//中点参数初值circPt.setCoords(0, radius);//Set coords for top point of circlevoid circlePlotPoints(GLint, GLint, screenPt);/*Plot the initial point in each circle quadrant*/circlePlotPoints(xc, yc, circPt);/*Calculate next point and plot in each octant*/while (circPt.getx() < circPt.gety()){circPt.incrementx();if (p < 0)p += 2 * circPt.getx() + 1;else{circPt.incrementy();p += 2 * (circPt.getx() - circPt.gety()) + 1;}circlePlotPoints(xc, yc, circPt);}}void circlePlotPoints(GLint xc, GLint yc, screenPt circPt){setPixel(xc + circPt.getx(), yc + circPt.gety());setPixel(xc - circPt.getx(), yc + circPt.gety());setPixel(xc + circPt.getx(), yc - circPt.gety());setPixel(xc - circPt.getx(), yc - circPt.gety());setPixel(xc + circPt.gety(), yc + circPt.getx());setPixel(xc - circPt.gety(), yc + circPt.getx());setPixel(xc + circPt.gety(), yc - circPt.getx());setPixel(xc - circPt.gety(), yc - circPt.getx());}void pieChart( ){screenPt circCtr, piePt;GLint radius = winWidth / 4;         // Circle radius.GLdouble sliceAngle, previousSliceAngle = 0.0;GLint k, nSlices = 12;               // Number of slices.GLfloat dataValues[12] = { 10.0, 7.0, 13.0, 5.0, 13.0, 14.0, 3.0, 16.0, 5.0, 3.0, 17.0, 8.0 };GLfloat dataSum = 0.0;circCtr.x = winWidth / 2;            // Circle center position.circCtr.y = winHeight / 2;circleMidpoint(circCtr.x, circCtr.y, radius);    // 调用中点画圆方法for (k = 0; k < nSlices; k++)dataSum += dataValues[k];for (k = 0; k < nSlices; k++){sliceAngle = twoPi * dataValues[k] / dataSum + previousSliceAngle;piePt.x = circCtr.x + radius * cos(sliceAngle);piePt.y = circCtr.y + radius * sin(sliceAngle);glBegin(GL_LINES);glVertex2i(circCtr.x, circCtr.y);glVertex2i(piePt.x, piePt.y);glEnd();previousSliceAngle = sliceAngle;}}void displayFcn( ){glClear(GL_COLOR_BUFFER_BIT);         // Clear display window.glColor3f(0.0, 0.0, 1.0);             // Set circle color to blue.pieChart();glFlush();}void winReshpeFcn(GLint newWidth, GLint newHeight){glMatrixMode(GL_PROJECTION);glLoadIdentity();gluOrtho2D(0.0, GLdouble(newWidth), 0.0, GLdouble(newHeight));glClear(GL_COLOR_BUFFER_BIT);/* Reset display-window size parameters. */winWidth = newWidth;winHeight = newHeight;}int _tmain(int argc, char** argv){glutInit(&argc, argv);glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);glutInitWindowPosition(100, 100);glutInitWindowSize(winWidth, winHeight);glutCreateWindow("Pie Chart");init();glutDisplayFunc(displayFcn);glutReshapeFunc(winReshpeFcn);glutMainLoop();}