OpenGL超级宝典学习笔记——操作像素

#include "gltools.h" #include  static GLbyte *pImage = NULL; static GLint iRenderMode = 0; static GLint iWidth, iHeight, iComponents; static GLenum eFormat; void ProcessMenu(int value)
{ if (value == 1)
    { //保存图像的快照 gltWriteTGA("screenshot.tga");
    } else {
        iRenderMode = value;
    }

    glutPostRedisplay();

} void RenderScene()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); if (!pImage)
    { return;
    } //设置光栅位置 glRasterPos2i(0, 0); //修改的图像，和用于反转的映射数组 GLbyte *pModifyImage = NULL;
  GLfloat invertMap[256]; switch (iRenderMode)
    { case 2: //图像倒转 glPixelZoom(-1.0f, -1.0f); //倒转后的图像的,渲染方向也倒转过来了，变成了从右上角开始往左下角渲染，所以设置倒转后的光栅位置为图像的宽高。 glRasterPos2i(iWidth, iHeight); break; case 3: //让图像填充满屏幕 GLint viewport[4]; //取得视口的大小 glGetIntegerv(GL_VIEWPORT, viewport); //按比例缩放 glPixelZoom((GLfloat)viewport[2]/iWidth, (GLfloat)viewport[3]/iHeight); break; case 4: //只保留红色 glPixelTransferf(GL_RED_SCALE, 1.0f);
    glPixelTransferf(GL_GREEN_SCALE, 0.0f);
    glPixelTransferf(GL_BLUE_SCALE, 0.0f); break; case 5: //只保留绿色 glPixelTransferf(GL_RED_SCALE, 0.0f);
    glPixelTransferf(GL_GREEN_SCALE, 1.0f);
    glPixelTransferf(GL_BLUE_SCALE, 0.0f); break; case 6: //只保留蓝色 glPixelTransferf(GL_RED_SCALE, 0.0f);
    glPixelTransferf(GL_GREEN_SCALE, 0.0f);
    glPixelTransferf(GL_BLUE_SCALE, 1.0f); break; case 7: //先渲染图像到颜色缓冲区中 glDrawPixels(iWidth, iHeight, eFormat, GL_UNSIGNED_BYTE, pImage); //NTSC标准,转成黑白图像  glPixelTransferf(GL_RED_SCALE, 0.3f);
    glPixelTransferf(GL_GREEN_SCALE, 0.59f);
    glPixelTransferf(GL_BLUE_SCALE, 0.11f); //申请临时空间来保存修改后的图像 pModifyImage = (GLbyte *)malloc(iWidth * iHeight * 3); if (!pModifyImage)
    { return;
    } //从颜色缓冲区中读取图像的亮度数据 glReadPixels(0, 0, iWidth, iHeight, GL_LUMINANCE, GL_UNSIGNED_BYTE, pModifyImage); //还原 glPixelTransferf(GL_RED_SCALE, 1.0f);
    glPixelTransferf(GL_GREEN_SCALE, 1.0f);
    glPixelTransferf(GL_BLUE_SCALE, 1.0f); break; case 8: //设置反转的颜色映射 invertMap[0] = 1.0f; for(int i = 0; i < 256; ++i)
    {
      invertMap[i] = 1.0f - (1.0f / 255.0f * (GLfloat)i);
    } //映射 glPixelMapfv(GL_PIXEL_MAP_R_TO_R, 255, invertMap);
    glPixelMapfv(GL_PIXEL_MAP_G_TO_G, 255, invertMap);
    glPixelMapfv(GL_PIXEL_MAP_B_TO_B, 255, invertMap); //开启颜色映射 glPixelTransferi(GL_MAP_COLOR, GL_TRUE); default: break;
    } if (pModifyImage)
  { //画黑白图像 glDrawPixels(iWidth, iHeight, GL_RGB, GL_UNSIGNED_BYTE, pModifyImage);
    free(pModifyImage);
  } else {
      glDrawPixels(iWidth, iHeight, eFormat, GL_UNSIGNED_BYTE, pImage);
  } //还原 glPixelTransferf(GL_RED_SCALE, 1.0f);
  glPixelTransferf(GL_GREEN_SCALE, 1.0f);
  glPixelTransferf(GL_BLUE_SCALE, 1.0f);
  glPixelZoom(1.0f, 1.0f);
  glPixelTransferi(GL_MAP_COLOR, GL_FALSE);
    glutSwapBuffers();
} void SetupRC()
{
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f); //设置像素的存储格式 glPixelStorei(GL_UNPACK_ALIGNMENT, 1); //加载图像数据 pImage = gltLoadTGA("horse.tga", &iWidth, &iHeight, &iComponents, &eFormat);

} //释放图像数据占用的内存空间 void ShutdownRC()
{ if (pImage)
    {
        free(pImage);
        pImage = NULL;
    }
} void ChangeSize(GLsizei w, GLsizei h)
{ if (h == 0)
        h = 1;

    glViewport(0, 0, w, h);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    gluOrtho2D(0.0, (GLdouble)w, 0.0, (GLdouble)h);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glutPostRedisplay();
} int main(int args, char **argv)
{
    glutInit(&args, argv);
    glutInitDisplayMode(GL_RGB | GL_DOUBLE);
    glutInitWindowSize(800, 600);
    glutCreateWindow("pixel operation");
    
    glutDisplayFunc(RenderScene);
    glutReshapeFunc(ChangeSize); //设置菜单 int menuID = glutCreateMenu(ProcessMenu);
    glutAddMenuEntry("Save Image", 1);
    glutAddMenuEntry("Flip", 2);
    glutAddMenuEntry("zoom pixel fill window", 3);
  glutAddMenuEntry("Just Red", 4);
  glutAddMenuEntry("Just Green", 5);
  glutAddMenuEntry("Just Blue", 6);
  glutAddMenuEntry("black & white", 7);
  glutAddMenuEntry("invert map", 8);
    glutAttachMenu(GLUT_RIGHT_BUTTON);

    SetupRC();
    glutMainLoop();
    ShutdownRC(); return 0;
}