OpenGL--位图

• 理论基础
  位图：就是对应一些二进制位来操作像素，0则表对应像素不绘制，1表绘制，这样来模拟绘制图像。一般可以用来绘制字符，但位图无法做缩放或旋转等特效。位图示例图如下：
  

  注：在opengl 3.0以后基本废弃了。

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• 实例代码

#include "GLTools.h"#include "GLShaderManager.h"#ifdef __APPLE__#include <glut/glut.h>#else#define FREEGLUT_STATIC#include <GL/glut.h>#endif//空格的位图GLubyte space[] ={0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};//26个字母的位图(二进制0对应像素不绘制，1则绘制)GLubyte letters[26][13] = {    {0x00, 0x00, 0xc3, 0xc3, 0xc3, 0xc3, 0xff, 0xc3, 0xc3, 0xc3, 0x66, 0x3c, 0x18},    {0x00, 0x00, 0xfe, 0xc7, 0xc3, 0xc3, 0xc7, 0xfe, 0xc7, 0xc3, 0xc3, 0xc7, 0xfe},    {0x00, 0x00, 0x7e, 0xe7, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xe7, 0x7e},    {0x00, 0x00, 0xfc, 0xce, 0xc7, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc7, 0xce, 0xfc},    {0x00, 0x00, 0xff, 0xc0, 0xc0, 0xc0, 0xc0, 0xfc, 0xc0, 0xc0, 0xc0, 0xc0, 0xff},    {0x00, 0x00, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xfc, 0xc0, 0xc0, 0xc0, 0xff},    {0x00, 0x00, 0x7e, 0xe7, 0xc3, 0xc3, 0xcf, 0xc0, 0xc0, 0xc0, 0xc0, 0xe7, 0x7e},    {0x00, 0x00, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xff, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3},    {0x00, 0x00, 0x7e, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x7e},    {0x00, 0x00, 0x7c, 0xee, 0xc6, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06},    {0x00, 0x00, 0xc3, 0xc6, 0xcc, 0xd8, 0xf0, 0xe0, 0xf0, 0xd8, 0xcc, 0xc6, 0xc3},    {0x00, 0x00, 0xff, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0},    {0x00, 0x00, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xdb, 0xff, 0xff, 0xe7, 0xc3},    {0x00, 0x00, 0xc7, 0xc7, 0xcf, 0xcf, 0xdf, 0xdb, 0xfb, 0xf3, 0xf3, 0xe3, 0xe3},    {0x00, 0x00, 0x7e, 0xe7, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xe7, 0x7e},    {0x00, 0x00, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xfe, 0xc7, 0xc3, 0xc3, 0xc7, 0xfe},    {0x00, 0x00, 0x3f, 0x6e, 0xdf, 0xdb, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0x66, 0x3c},    {0x00, 0x00, 0xc3, 0xc6, 0xcc, 0xd8, 0xf0, 0xfe, 0xc7, 0xc3, 0xc3, 0xc7, 0xfe},    {0x00, 0x00, 0x7e, 0xe7, 0x03, 0x03, 0x07, 0x7e, 0xe0, 0xc0, 0xc0, 0xe7, 0x7e},    {0x00, 0x00, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0xff},    {0x00, 0x00, 0x7e, 0xe7, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3},    {0x00, 0x00, 0x18, 0x3c, 0x3c, 0x66, 0x66, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3},    {0x00, 0x00, 0xc3, 0xe7, 0xff, 0xff, 0xdb, 0xdb, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3},    {0x00, 0x00, 0xc3, 0x66, 0x66, 0x3c, 0x3c, 0x18, 0x3c, 0x3c, 0x66, 0x66, 0xc3},    {0x00, 0x00, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x3c, 0x3c, 0x66, 0x66, 0xc3},    {0x00, 0x00, 0xff, 0xc0, 0xc0, 0x60, 0x30, 0x7e, 0x0c, 0x06, 0x03, 0x03, 0xff}};GLuint fontOffset;void makeRasterFont(void){    GLuint i, j;    /*设置像素的储存模式，参数1包括：GL_PACK_ALIGNMENT：打包    与GL_UNPACK_ALIGNMENT：解包两种。参数2是对齐方式，如这里    是取字母，一个字母占1字节，所以以1字节对齐*/    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);    fontOffset = glGenLists (128);//申请了128个索引作为显示列表标志    for (i = 0,j = 'A'; i < 26; i++,j++) {        glNewList(fontOffset + j, GL_COMPILE);//以字母对应的ASCII码作为索引标志        glBitmap(8, 13, 0.0, 2.0, 10.0, 0.0, letters[i]);//绘制26个字母位图        glEndList();    }    glNewList(fontOffset + ' ', GL_COMPILE);    glBitmap(8, 13, 0.0, 2.0, 10.0, 0.0, space);//绘制空格    glEndList();}void init(void){    glShadeModel (GL_FLAT);    makeRasterFont();}void printString(char *s){    /*属性堆栈*/    glPushAttrib (GL_LIST_BIT);        glListBase(fontOffset);//指定偏移量        /*参数：执行strlen(s)个显示列表，对应执行的         显示列表索引值 = *s + 对应偏移(按字节递加)*/        glCallLists(strlen(s), GL_UNSIGNED_BYTE,         (GLubyte *) s);//一次执行多个显示列表    glPopAttrib ();}void display(void){    GLfloat white[3] = { 1.0, 1.0, 1.0 };    glClear(GL_COLOR_BUFFER_BIT);    glColor3fv(white);    glRasterPos2i(25, 60);//光栅位置    printString("THE QUICK BROWN FOX JUMPS");    glRasterPos2i(25, 40);    printString("OVER A LAZY DOG");    glFlush ();}void reshape(int w, int h){    glViewport(0, 0, (GLsizei) w, (GLsizei) h);    glMatrixMode(GL_PROJECTION);    glLoadIdentity();    glOrtho (0.0, w, 0.0, h, -1.0, 1.0);    glMatrixMode(GL_MODELVIEW);}int main(int argc, char** argv){    glutInit(&argc, argv);    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);    glutInitWindowSize(300, 100);    glutInitWindowPosition (100, 100);    glutCreateWindow(argv[0]);    init();    glutReshapeFunc(reshape);    glutDisplayFunc(display);    glutMainLoop();    return 0;}