OpenGL编程轻松入门之像素操作
2006-05-23 08:35作者:黄燕出处:天极开发责任编辑:方舟
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