在本文中，任务是使用OpenGL在计算机屏幕上创建不同的图形。
方法：
- 在本文中，为了用颜色填充图形，使用了不同的算法，因此可以以优化的图案进行填充。
- 在这里，将使用具有子窗口概念的C++程序中实现的泛洪填充和边界填充算法。
- 该程序中使用mouse()函数。运行该程序后，使用左键单击绘制图像，然后右键单击以填充图像。
下面是说明OpenGL使用的C++程序：
C++
// C++ program to illustrate the use
// of OpenGL
#include
#include
#include
#include
#include
#define xpix 500
#include
using namespace std;
// Global variable declaration
float r, g, b, x, y;
bool flag = true;
int x2, y2, x3, y3, x4, y4, x5, y5;
int a1, b1;
int a2, b2;
int a3, b3;
int a4, b4;
int counter = 1;
char buffer[20];
// Function to draw text
void drawBitmapText(
char* string, float x,
float y, float z)
{
char* c;
glRasterPos2f(x, y);
// Traverse the given string
for (c = string; *c != '\0'; c++) {
// Initialize gluBitmap
glutBitmapCharacter(
GLUT_BITMAP_TIMES_ROMAN_24, *c);
}
}
// Function for performing the delay
void delay(float ms)
{
clock_t goal = ms + clock();
// Iterate until goal is greater
// than the clock
while (goal > clock())
;
}
// Funciton to initialize the figure
void init()
{
glClearColor(1.0, 1.0, 1.0, 0.0);
glColor3f(0.0, 0.0, 0.0);
glPointSize(1.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0, 800, 0, 600);
}
// Function to fill the color in the
// figure
void bound_it(int x, int y,
float* fillColor,
float* bc)
{
float color[3];
// Initialize to read the pixels
glReadPixels(x, y, 1.0, 1.0,
GL_RGB, GL_FLOAT, color);
if ((color[0] != bc[0]
|| color[1] != bc[1]
|| color[2] != bc[2])
&& (color[0] != fillColor[0]
|| color[1] != fillColor[1]
|| color[2] != fillColor[2])) {
// Fill the Color
glColor3f(fillColor[0],
fillColor[1],
fillColor[2]);
// Begin the GL Points
glBegin(GL_POINTS);
// Initialize the vertex
glVertex2i(x, y);
glEnd();
glFlush();
// Fill the color
bound_it(x + 1, y, fillColor, bc);
bound_it(x - 2, y, fillColor, bc);
bound_it(x, y + 2, fillColor, bc);
bound_it(x, y - 2, fillColor, bc);
}
}
// Function to fill the figure using
// the mouse click operation
void mouseboundaryfill(int btn, int state,
int x, int y)
{
// Boundary fill algorithm
y = 600 - y;
// If the right button is clicked
if (btn == GLUT_RIGHT_BUTTON) {
if (state == GLUT_DOWN) {
float bCol[] = { 1, 0, 0 };
float color[] = { 0, 1, 1 };
bound_it(x, y, color, bCol);
}
}
// If the left button is clicked
if (btn == GLUT_LEFT_BUTTON) {
if (state == GLUT_DOWN) {
if (counter == 1) {
a1 = x;
b1 = y;
counter++;
}
else if (counter == 2) {
a2 = x;
b2 = y;
counter++;
}
else if (counter == 3) {
a3 = x;
b3 = y;
counter++;
}
else if (counter == 4) {
a4 = x;
b4 = y;
counter = 0;
}
}
}
}
// Function to implement the world()
void world()
{
glLineWidth(3);
glPointSize(2);
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1, 0, 0);
glBegin(GL_LINE_LOOP);
// Initialize a vertices
glVertex2f(a1, b1);
glVertex2f(a2, b2);
glVertex2f(a3, b3);
glVertex2f(a4, b4);
glEnd();
// Fill the color
glColor3f(0, 0, 0);
glFlush();
}
// Function to inilialize the figure
void init2()
{
glClearColor(1.0, 1.0, 0.0, 0.0);
glMatrixMode(GL_PROJECTION);
gluOrtho2D(0, 400, 0, 600);
}
// Structure for Points
struct Point {
GLint x;
GLint y;
};
// Structure for Colors
struct Color {
GLfloat r;
GLfloat g;
GLfloat b;
};
// Structure for getting the Pixels
Color getPixelColor(GLint x, GLint y)
{
Color color;
glReadPixels(x, y, 1, 1,
GL_RGB,
GL_FLOAT,
&color);
return color;
}
// Function for setting the pixel color
void setPixelColor(GLint x, GLint y,
Color color)
{
// Fill the Color
glColor3f(color.r, color.g, color.b);
// Begin the GL Points
glBegin(GL_POINTS);
// Initialize the vertex
glVertex2i(x, y);
glEnd();
glFlush();
}
// Function to fill the figure using
// floodfill function
void floodFill(GLint x, GLint y,
Color oldColor,
Color newColor)
{
// Flood fill algorithm
Color color;
color = getPixelColor(x, y);
if (color.r == oldColor.r
&& color.g == oldColor.g
&& color.b == oldColor.b) {
setPixelColor(x, y, newColor);
// Fill the color
floodFill(x + 1, y, oldColor,
newColor);
floodFill(x, y + 1, oldColor,
newColor);
floodFill(x - 1, y, oldColor,
newColor);
floodFill(x, y - 1, oldColor,
newColor);
}
return;
}
// Function to fill the color using
// mouse click operation
void mousefloodfill(int button, int state,
int x, int y)
{
// Left Click
if (button == GLUT_LEFT_BUTTON
&& state == GLUT_DOWN) {
flag = true;
x2 = x;
y2 = 600 - y;
}
// Right Click
else if (button == GLUT_RIGHT_BUTTON
&& state == GLUT_DOWN) {
Color newColor = { 0.0f, 0.0f, 1.0f };
Color oldColor = { 1.0f, 1.0f, 1.0f };
// Fill the color
floodFill(x2, y2, oldColor, newColor);
}
glutPostRedisplay();
}
// Function to draw the circle on
// the plane
void draw_circle(Point pC,
GLfloat radius)
{
if (flag) {
GLfloat step = 1 / radius;
GLfloat x, y;
for (GLfloat theta = 0; theta <= 360;
theta += step) {
x = pC.x + (radius * cos(theta));
y = pC.y + (radius * sin(theta));
glVertex2i(x, y);
}
}
}
// Function to display the figure
void display(void)
{
Point pt = { x2, y2 };
GLfloat radius = 70;
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_POINTS);
draw_circle(pt, radius);
glEnd();
glFlush();
}
// Driver Code
int main(int argc, char** argv)
{
glutInit(&argc, argv);
// Function calls
glutInitDisplayMode(
GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(800, 600);
glutInitWindowPosition(100, 100);
int mainWindow
= glutCreateWindow(
"<-- Boundary Fill on left || "
"Flood fill on Right -->");
init();
glutDisplayFunc(display);
glutMouseFunc(mousefloodfill);
int subWindow1
= glutCreateSubWindow(
mainWindow, 0, 0, 400, 600);
glutInitWindowPosition(100, 100);
glutDisplayFunc(world);
glutMouseFunc(mouseboundaryfill);
init2();
glutMainLoop();
return 0;
} 输出
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