OpenGL编程轻松入门之像素操作

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　　本节讲解像素操作。　　例14：本例在窗口绘制一个三角形，然后利用glCopyPixel函数拷贝了五次该图形，并将这五个三角形放置在窗口的不同位置。 #include #include /*设置背景色*/void myInit(void){　glClearColor(1.0,1.0,1.0,1.0);}/*绘制彩色三角形*/void triangle(void){　glBegin(GL_TRIANGLES);　glColor3f(1.0,1.0,0.0);　glVertex2f(10.0,10.0);　glColor3f(0.0,0.3,1.0);　glVertex2f(20.0,30.0);　glColor3f(1.0,0.0,0.0);　glVertex2f(30.0,10.0);　glEnd();}void myDisplay(){　int i;　glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);　glPushMatrix();　glTranslatef(10.0,100.0,0.0);　triangle();　glPopMatrix();　glPushMatrix();　for(i = 0;i < 5;i )　{　　glRasterPos2i(20 i*30,10 i*5);//为像素操作指定光栅位置　　glCopyPixels(50,200,500,500,GL_COLOR);//在缓存中拷贝像素 　}　glPopMatrix();　glFlush();}void myReshape(int w,int h){　glViewport(0,0,(GLsizei)w,(GLsizei)h);　glMatrixMode(GL_PROJECTION);　glLoadIdentity();　if( w <= h)　　gluOrtho2D(0.0,150,0.0,150.0*(GLfloat)h/(GLfloat)w);　else　　gluOrtho2D(0.0,150*(GLfloat)w/(GLfloat)h,0.0,150.0);　glMatrixMode(GL_MODELVIEW);　glLoadIdentity();}int main(int argc,char ** argv){　glutInit(&argc,argv);　glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB|GLUT_DEPTH);　glutInitWindowSize(500,400);　glutInitWindowPosition(100,100);　glutCreateWindow(" copy ");　myInit();　glutReshapeFunc(myReshape);　glutDisplayFunc(myDisplay);　glutMainLoop();　return 0;}　　·glRasterPos在像素操作中指定光栅位置。同样后面的数字表示坐标维数，2表示坐标为x、y，3表示、，y、z。数字后面的字母表示参数类型。最后带V表示参数为指针。　　·void glCopyPixels（GLint x, Glint y, GLsizei width, GLsizei height, GLenum type）函数将像素拷贝到缓存中。　　x，y指定被拷贝像素的右下角坐标。　　width，heigth指定被拷贝像素矩形区域的大小。　　type指定拷贝数值的类型。值为颜色、深度或膜板值。本例中为颜色。　　例15：此例在窗口左下角写单词FILE。 #include #include /*字母F*/GLubyte f_rasters[12] = {0xc0,0xc0,0xc0,0xc0,0xc0,0xfc,0xfc,0xc0,0xc0,0xc0,0xff,0xff};/*字母I*/GLubyte i_rasters[12] = {0xff,0xff,0x18,0x18,0x18,0x18,0x18,0x18,0x18,0x18,0xff,0xff};/*字母L*/GLubyte l_rasters[12] = {0xff,0xff,0xc0,0xc0,0xc0,0xc0,0xc0,0xc0,0xc0,0xc0,0xc0,0xc0};/*字母E*/GLubyte e_rasters[12] = {0xff,0xff,0xc0,0xc0,0xc0,0xff,0xff,0xc0,0xc0,0xc0,0xff,0xff};void myInit(void){　glPixelStorei(GL_UNPACK_ALIGNMENT,1);//设置像素存储模式　glClearColor(1.0,1.0,1.0,1.0);//设置背景为白色}void myDisplay(){　glClear(GL_COLOR_BUFFER_BIT);　glColor3f(0.0,0.0,0.0);//设置像素颜色为黑色　glRasterPos2i(20,20);//为像素指定位置　/*绘制位图*/　glBitmap(8,12,0.0,0.0,14.0,0.0,f_rasters);　glBitmap(8,12,0.0,0.0,14.0,0.0,i_rasters);　glBitmap(8,12,0.0,0.0,14.0,0.0,l_rasters);　glBitmap(8,12,0.0,0.0,14.0,0.0,e_rasters);　glFlush();}void myReshape(int w,int h){　glViewport(0,0,(GLsizei)w,(GLsizei)h);　glMatrixMode(GL_PROJECTION);　glLoadIdentity();　glOrtho(0,w,0,h,-1.0,1.0);　glMatrixMode(GL_MODELVIEW);　glLoadIdentity();}int main(int argc,char ** argv){　/*初始化*/　glutInit(&argc,argv);　glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);　glutInitWindowSize(500,400);　glutInitWindowPosition(100,100);　/*创建窗口*/　glutCreateWindow(" BitMap");　/*绘制图形*/　myInit();　glutReshapeFunc(myReshape);　glutDisplayFunc(myDisplay);　glutMainLoop();//进入GLUT事件处理循环　return 0;}　　·glBitmap（GLsizei width，GLsizei height，GLfloat xorig，GLfloat yorig，GLfloat xmove，GLfloat ymove，const GLubyte *bitmap）函数绘制一个位图。　　width，height分别指定位图图像的宽度和高度。　　xorig，yorig位图图像的原点位置。原点为位图的左下角。向右和向上为坐标轴的正向。　　xmove，ymove绘制完位图后x，y相对于当前光栅的位移。　　bitmap位图图像的地址。　　你可以改变此函数的参数，观察不同大小不同位置的效果。 　　本节讲解像素操作。　　例14：本例在窗口绘制一个三角形，然后利用glCopyPixel函数拷贝了五次该图形，并将这五个三角形放置在窗口的不同位置。 #include #include /*设置背景色*/void myInit(void){　glClearColor(1.0,1.0,1.0,1.0);}/*绘制彩色三角形*/void triangle(void){　glBegin(GL_TRIANGLES);　glColor3f(1.0,1.0,0.0);　glVertex2f(10.0,10.0);　glColor3f(0.0,0.3,1.0);　glVertex2f(20.0,30.0);　glColor3f(1.0,0.0,0.0);　glVertex2f(30.0,10.0);　glEnd();}void myDisplay(){　int i;　glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);　glPushMatrix();　glTranslatef(10.0,100.0,0.0);　triangle();　glPopMatrix();　glPushMatrix();　for(i = 0;i < 5;i )　{　　glRasterPos2i(20 i*30,10 i*5);//为像素操作指定光栅位置　　glCopyPixels(50,200,500,500,GL_COLOR);//在缓存中拷贝像素 　}　glPopMatrix();　glFlush();}void myReshape(int w,int h){　glViewport(0,0,(GLsizei)w,(GLsizei)h);　glMatrixMode(GL_PROJECTION);　glLoadIdentity();　if( w <= h)　　gluOrtho2D(0.0,150,0.0,150.0*(GLfloat)h/(GLfloat)w);　else　　gluOrtho2D(0.0,150*(GLfloat)w/(GLfloat)h,0.0,150.0);　glMatrixMode(GL_MODELVIEW);　glLoadIdentity();}int main(int argc,char ** argv){　glutInit(&argc,argv);　glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB|GLUT_DEPTH);　glutInitWindowSize(500,400);　glutInitWindowPosition(100,100);　glutCreateWindow(" copy ");　myInit();　glutReshapeFunc(myReshape);　glutDisplayFunc(myDisplay);　glutMainLoop();　return 0;}　　·glRasterPos在像素操作中指定光栅位置。同样后面的数字表示坐标维数，2表示坐标为x、y，3表示、，y、z。数字后面的字母表示参数类型。最后带V表示参数为指针。　　·void glCopyPixels（GLint x, Glint y, GLsizei width, GLsizei height, GLenum type）函数将像素拷贝到缓存中。　　x，y指定被拷贝像素的右下角坐标。　　width，heigth指定被拷贝像素矩形区域的大小。　　type指定拷贝数值的类型。值为颜色、深度或膜板值。本例中为颜色。　　例15：此例在窗口左下角写单词FILE。 #include #include /*字母F*/GLubyte f_rasters[12] = {0xc0,0xc0,0xc0,0xc0,0xc0,0xfc,0xfc,0xc0,0xc0,0xc0,0xff,0xff};/*字母I*/GLubyte i_rasters[12] = {0xff,0xff,0x18,0x18,0x18,0x18,0x18,0x18,0x18,0x18,0xff,0xff};/*字母L*/GLubyte l_rasters[12] = {0xff,0xff,0xc0,0xc0,0xc0,0xc0,0xc0,0xc0,0xc0,0xc0,0xc0,0xc0};/*字母E*/GLubyte e_rasters[12] = {0xff,0xff,0xc0,0xc0,0xc0,0xff,0xff,0xc0,0xc0,0xc0,0xff,0xff};void myInit(void){　glPixelStorei(GL_UNPACK_ALIGNMENT,1);//设置像素存储模式　glClearColor(1.0,1.0,1.0,1.0);//设置背景为白色}void myDisplay(){　glClear(GL_COLOR_BUFFER_BIT);　glColor3f(0.0,0.0,0.0);//设置像素颜色为黑色　glRasterPos2i(20,20);//为像素指定位置　/*绘制位图*/　glBitmap(8,12,0.0,0.0,14.0,0.0,f_rasters);　glBitmap(8,12,0.0,0.0,14.0,0.0,i_rasters);　glBitmap(8,12,0.0,0.0,14.0,0.0,l_rasters);　glBitmap(8,12,0.0,0.0,14.0,0.0,e_rasters);　glFlush();}void myReshape(int w,int h){　glViewport(0,0,(GLsizei)w,(GLsizei)h);　glMatrixMode(GL_PROJECTION);　glLoadIdentity();　glOrtho(0,w,0,h,-1.0,1.0);　glMatrixMode(GL_MODELVIEW);　glLoadIdentity();}int main(int argc,char ** argv){　/*初始化*/　glutInit(&argc,argv);　glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);　glutInitWindowSize(500,400);　glutInitWindowPosition(100,100);　/*创建窗口*/　glutCreateWindow(" BitMap");　/*绘制图形*/　myInit();　glutReshapeFunc(myReshape);　glutDisplayFunc(myDisplay);　glutMainLoop();//进入GLUT事件处理循环　return 0;}　　·glBitmap（GLsizei width，GLsizei height，GLfloat xorig，GLfloat yorig，GLfloat xmove，GLfloat ymove，const GLubyte *bitmap）函数绘制一个位图。　　width，height分别指定位图图像的宽度和高度。　　xorig，yorig位图图像的原点位置。原点为位图的左下角。向右和向上为坐标轴的正向。　　xmove，ymove绘制完位图后x，y相对于当前光栅的位移。　　bitmap位图图像的地址。　　你可以改变此函数的参数，观察不同大小不同位置的效果。 下载本文示例代码


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