OpenGL学习二十四：绘制像素，位图，图像

除了几何图形的渲染，还有两种重要的类型的数据渲染
位图:由0和1组成的矩形数组（采用黑白，0为黑1，为白）
图像数据：每个像素包含好几段数据（RGBA）

 

当前光栅位置
当前光栅位置就是开始绘制下一副位图或图像的屏幕位置,光栅坐标需要经过模型投影矩阵变换
glRasterPos{234}{sifd} (TYPE x, TYPE y,TYPE z,TYPE w);

当前窗口位置
glWindowPos{23}{sifd} (TYPE x, TYPE y,TYPE z);
设置当前窗口位置，不需要经过模型投影矩阵变换

glOrtho (-20, 80, 0, h, -1.0, 1.0);
左图1：光栅坐标
右图2：窗口坐标

              

 

绘制位图
glBitmap (GLsizei width, GLsizei height, GLfloat xorig, GLfloat yorig, GLfloat xmove, GLfloat ymove, const GLubyte *bitmap);

xorig,yorig定义了光栅的原点，它根据当前光栅位置确定的，正值在当前光栅的上面和右面，负值在当前的下面和左面
xmove，ymove表示位图光栅化后光栅位置的增加量

说明：如果位图信息数据包含N个字节，位图高度为M，那么每行所包含的字节数为n/m根据此内容渲染位图0,1 来达到期望的效果

 

图像
void glReadPixels (GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid *pixels);

从帧缓冲区读取一个矩形像素数组，并把数据保存在内存中
glDrawPixels (GLsizei width, GLsizei height, GLenum format, GLenum type, const GLvoid *pixels);

把内存中保存的一个矩形像素数组写入到帧缓冲区中由glRasterPos指定的当前位置
glCopyPixels (GLint x, GLint y, GLsizei width, GLsizei height, GLenum buffer);
从帧缓冲区读取一个矩形像素数组，并把数据保存在内存中
buffer：GL_DEPTH(GL_DEPTH_COMPONENT)
        GL_STENCIL(GL_STENCIL_INDEX)
        GL_COLOR(GL_RGBA或GL_COLOR_INDEX)

 

放大，缩小或旋转图像
void glPixelZoom(Glfloat zoomx,Glfloat zoomy)
设置像素的写入操作glDrawPixels,glCopyPixels中x,y方向的放大或缩小因子，默认值都是1.0,如果它们都是2.0，图像每个像素被绘制4个屏幕像素，可以使用负的缩放因子，负的缩放因子根据当前光栅位置对图像进行翻转。正常图片是自底向上，从左到用，如果Y为负数，图像映射到屏幕上就是自顶向下的

 glRasterPos2i(0, 0);
   //glPixelZoom (2, 2);//1
   glDrawPixels(checkImageWidth, checkImageHeight, GL_RGB,  GL_UNSIGNED_BYTE, checkImage);
   //glPixelZoom (1, 1);//2
   glRasterPos2i (250, 0);
 glCopyPixels(0,0,checkImageWidth,checkImageHeight,GL_COLOR);

左边的图为glDrawPixels,右边的图是glCopyPixels

将1,2处解开，可见DrawPixels大小放大2*2倍，glCopyPixels在2*2倍 再次放大1*1倍

将1,2处解开，可见DrawPixels大小放大2*2倍，glCopyPixels在2*2倍 再次放大1*1倍

由此可见不显示调用glPixelZoom (1, 1)，默认与使用原来放大倍数再次放大

 

glReadPixels与glDrawPixels所使用的像素格式

GL_COLOR	1个颜色索引值
GL_RG
GL_RGB
GL_RGBA
GL_BGR
GL_BGRA
GL_RED
GL_GREEN
GL_BLUE
GL_ALPHA
GL_LUMINANCE	一个亮度成分
GL_LUMINANCE_ALPHA	一个亮度成分和一个alpha成分
GL_STENCIL_INDEX	一个模板索引值
GL_DEPTH_COMPONENT	一个深度成分
GL_DEPTH_STENCIL	深度成分和模板成分混合

 glReadPixels与glDrawPixels所使用的数据类型

GL_UNSIGNED_BYTE
GL_BYTE
GL_BITMAP
GL_UNSIGNED_SHORT
GL_SHORT
GL_UNSIGNED_INT
GL_INT
GL_FLOAT
GL_HALF_FLOAT
GL_UNSIGNED_BYTE_3_3_2
GL_UNSIGNED_BYTE_2_3_3_REV	REV后缀专门用于微软操作系统
GL_UNSIGNED_SHORT_5_6_5
GL_UNSIGNED_SHORT_5_6_5_REV
GL_UNSIGNED_SHORT_4_4_4_4
GL_UNSIGNED_SHORT_4_4_4_4_REV
GL_UNSIGNED_SHORT_5_5_5_1
GL_UNSIGNED_SHORT_1_5_5_5_REV
GL_UNSIGNED_INT_8_8_8_8
GL_UNSIGNED_INT_8_8_8_8_REV
GL_UNSIGNED_INT_10_10_10_2
GL_UNSIGNED_INT_2_10_10_10_REV
GL_UNSIGNED_INT_24_8

 

像素格式与数据类型匹配关系

GL_UNSIGNED_BYTE_3_3_2	GL_RGB
GL_UNSIGNED_BYTE_2_3_3_REV	GL_RGB
GL_UNSIGNED_SHORT_5_6_5	GL_RGB
GL_UNSIGNED_SHORT_5_6_5_REV	GL_RGB
GL_UNSIGNED_SHORT_4_4_4_4	GL_RGBA,GL_BGRA
GL_UNSIGNED_SHORT_4_4_4_4_REV	GL_RGBA,GL_BGRA
GL_UNSIGNED_SHORT_5_5_5_1	GL_RGBA,GL_BGRA
GL_UNSIGNED_SHORT_1_5_5_5_REV	GL_RGBA,GL_BGRA
GL_UNSIGNED_INT_8_8_8_8	GL_RGBA,GL_BGRA
GL_UNSIGNED_INT_8_8_8_8_REV	GL_RGBA,GL_BGRA
GL_UNSIGNED_INT_10_10_10_2	GL_RGBA,GL_BGRA
GL_UNSIGNED_INT_2_10_10_10_REV	GL_RGBA,GL_BGRA
GL_UNSIGNED_INT_24_8	GL_DEPTH_STENCIL
GL_UNSIGNED_INT_10F_11F_11F	GL_RGB
GL_UNSIGNED_INT_5_9_9_9_REV	GL_RGB
GL_FLOAT_32_UNSIGNED_INT_24_8_REV	GL_DEPTH_STENCIL

 

位图DEMO

#include "header.h"	
#include <string.h>

GLubyte space[] = 
{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

GLubyte letters[][13] = {
{0x00, 0x00, 0xc3, 0xc3, 0xc3, 0xc3, 0xff, 0xc3, 0xc3, 0xc3, 0x66, 0x3c, 0x18}, //a
{0x00, 0x00, 0xfe, 0xc7, 0xc3, 0xc3, 0xc7, 0xfe, 0xc7, 0xc3, 0xc3, 0xc7, 0xfe}, //b
{0x00, 0x00, 0x7e, 0xe7, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xe7, 0x7e}, //c
{0x00, 0x00, 0xfc, 0xce, 0xc7, 0xc3, 0xc3, 0xc3, 0xc3, 0xc3, 0xc7, 0xce, 0xfc}, //d
{0x00, 0x00, 0xff, 0xc0, 0xc0, 0xc0, 0xc0, 0xfc, 0xc0, 0xc0, 0xc0, 0xc0, 0xff}, //e
{0xc0, 0x00, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xc0, 0xfc, 0xc0, 0xc0, 0xc0, 0xff}, //f
{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;
   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

   fontOffset = glGenLists (128);
   for (i = 0,j = 'A'; i < 26; i++,j++) {
      glNewList(fontOffset + j, GL_COMPILE);
      glBitmap(8, 13, 0.0, 2.0, 10.0, 0.0, letters[i]);
      glEndList();
   }
   glNewList(fontOffset + ' ', GL_COMPILE);
   glBitmap(8, 13, 0.0, 2.0, 10.0, 0.0, space);
   glEndList();
}

void init(void)
{
   glShadeModel (GL_FLAT);
   makeRasterFont();
}

void printString(char *s)
{
   glPushAttrib (GL_LIST_BIT);
   glListBase(fontOffset);
   glCallLists(strlen(s), GL_UNSIGNED_BYTE, (GLubyte *) s);
   glPopAttrib ();
}


void display(void)
{
   GLfloat white[3] = { 1.0, 1.0, 1.0 };

   glClear(GL_COLOR_BUFFER_BIT);
   glColor3fv(white);

   glRasterPos2i(20, 60);
   printString("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
   glRasterPos2i(20, 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);
}

void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 27:
         exit(0);
   }
}


int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize(300, 100);
   glutInitWindowPosition (100, 100);
   glutCreateWindow("位图");
   init();
   glutReshapeFunc(reshape);
   glutKeyboardFunc(keyboard);
   glutDisplayFunc(display);
   glutMainLoop();
   return 0;
}

 

绘制像素DEMO

#include "header.h"

/*	Create checkerboard image	*/
#define	checkImageWidth 64
#define	checkImageHeight 64
GLubyte checkImage[checkImageHeight][checkImageWidth][3];

static GLdouble zoomFactor = 1.0;
static GLint height;


void makeCheckImage(void)
{
   int i, j, c;
    
   for (i = 0; i < checkImageHeight; i++) {
      for (j = 0; j < checkImageWidth; j++) {
         c = ((((i&0x8)==0)^((j&0x8))==0))*255;
         checkImage[i][j][0] = (GLubyte) c;
         checkImage[i][j][1] = (GLubyte) c;
         checkImage[i][j][2] = (GLubyte) c;
      }
   }
}

void init(void)
{    
   glClearColor (0.0, 0.0, 0.0, 0.0);
   glShadeModel(GL_FLAT);
   makeCheckImage();
   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
}

void display(void)
{
   glClear(GL_COLOR_BUFFER_BIT);
   glRasterPos2i(0, 0);
   glPixelZoom (2, 2);
   glDrawPixels(checkImageWidth, checkImageHeight, GL_RGB, 
	   GL_UNSIGNED_BYTE, checkImage);
   //glPixelZoom (1, 1);
   glRasterPos2i (250, 0);

   glCopyPixels(0,0,checkImageWidth,checkImageHeight,GL_COLOR);
   glFlush();
}

void reshape(int w, int h)
{
   glViewport(0, 0, (GLsizei) w, (GLsizei) h);
   height = (GLint) h;
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   gluOrtho2D(0.0, (GLdouble) w, 0, (GLdouble) h);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}


void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 'r':
      case 'R':
         zoomFactor = 1.0;
         glutPostRedisplay();
         printf ("zoomFactor reset to 1.0\n");
         break;
      case 'z':
         zoomFactor += 0.5;
         if (zoomFactor >= 3.0) 
            zoomFactor = 3.0;
         printf ("zoomFactor is now %4.1f\n", zoomFactor);
         break;
      case 'Z':
         zoomFactor -= 0.5;
         if (zoomFactor <= 0.5) 
            zoomFactor = 0.5;
         printf ("zoomFactor is now %4.1f\n", zoomFactor);
         break;
      case 27:
         exit(0);
         break;
      default:
         break;
   }
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize(512, 512);
   glutInitWindowPosition(100, 100);
   glutCreateWindow("绘制像素");
   init();
   glutDisplayFunc(display);
   glutReshapeFunc(reshape);
   glutKeyboardFunc(keyboard);
   glutMainLoop();
   return 0; 
}