C++ SDL2和x2B；OpenGL&x2B；SDL2_TTF：显示文本

我在OpenGL plus SDL2.0中绘制TTF字体时遇到问题

我记得在SDL版本2之前，我没有遇到任何问题，但似乎缺少关于这个主题的文档，可能是由于新标准的缘故

我已经包含了下面的代码来大致说明我在做什么

这段代码效率很低，因为我每帧都重新创建纹理，如果复制+粘贴，请考虑这一点：）

void main_render（）{
glClear（GL_颜色_缓冲_位| GL_深度_缓冲_位）；
//将颜色设置回白色（全纹理颜色）
GL3F（1.0f，1.0f，1.0f）；
主摄像头->透视（）；
mainCamera->translate（）；
//加载字体
TTF_Font*Font=TTF_OpenFont（“../resource/Font.TTF”，10）；
如果（字体==nullptr）{
std:：cout所以OpenGL要求我的系统上所有纹理的尺寸都是Base2（2,4,16,32,64…）

我通过增量搜索与原始维度最接近的二次幂来修复此问题：

  unsigned int power_two_floor(unsigned int val) {
    unsigned int power = 2, nextVal = power*2;

    while((nextVal *= 2) <= val)
      power*=2;

    return power*2;
  }

需要添加过滤器信息才能更正OpenGL使用mipmaps的错误：

 //Avoid mipmap filtering
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

以下是我的答案：

unsigned int power_two_floor(unsigned int val) {
  unsigned int power = 2, nextVal = power*2;
  while((nextVal *= 2) <= val)
    power*=2;
  return power*2;
}

void main_render() {
  //Load the font
  TTF_Font *font = TTF_OpenFont("../resource/font.ttf", 10);
  if (font == nullptr) {
    std::cout << "TTF_OpenFont error: " << std::endl;
    return;
  }

  SDL_Color colorFg = {0,0,255};
  SDL_Surface *surface;

  //Render font to a SDL_Surface
  if ((surface = TTF_RenderText_Blended(font, "Hi!", colorFg)) == nullptr) {
    TTF_CloseFont(font);
    std::cout << "TTF_RenderText error: " << std::endl;
    return;
  }

  GLuint texId;

  //Generate OpenGL texture
  glEnable(GL_TEXTURE_2D);
  glGenTextures(1, &texId);
  glBindTexture(GL_TEXTURE_2D, texId);

  //Avoid mipmap filtering
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

  //Find the first power of two for OpenGL image 
  int w = power_two_floor(surface->w)*2;
  int h = power_two_floor(surface->h)*2;

  //Create a surface to the correct size in RGB format, and copy the old image
  SDL_Surface * s = SDL_CreateRGBSurface(0, w, h, 32, 0x00ff0000,0x0000ff00,0x000000ff,0xff000000);
  SDL_BlitSurface(surface, NULL, s, NULL);

  //Copy the created image into OpenGL format
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, s->pixels);

  //Draw the OpenGL texture as a Quad
  glBegin(GL_QUADS); {
    glTexCoord2d(0, 1); glVertex3f(0,              0,              0);
    glTexCoord2d(1, 1); glVertex3f(0 + surface->w, 0,              0);
    glTexCoord2d(1, 0); glVertex3f(0 + surface->w, 0 + surface->h, 0);
    glTexCoord2d(0, 0); glVertex3f(0,              0 + surface->h, 0); 
  } glEnd();
  glDisable(GL_TEXTURE_2D);

  //Cleanup
  TTF_CloseFont(font);
  SDL_FreeSurface(s);
  SDL_FreeSurface(surface);
  glDeleteTextures(1, &texId);
}

unsigned int power\u two\u floor（unsigned int val）{
无符号整数幂=2，nextVal=幂*2；
而（（nextVal*=2）w，0+表面->h，0）；
glTexCoord2d（0,0）；glVertex3f（0,0+表面->h,0）；
}格伦德（）；
glDisable（GL_纹理_2D）；
//清理
TTF_关闭字体（字体）；
SDL_自由曲面（s）；
SDL_自由曲面（曲面）；
glDeleteTextures（1，&texId）；
}

 //Avoid mipmap filtering
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

unsigned int power_two_floor(unsigned int val) {
  unsigned int power = 2, nextVal = power*2;
  while((nextVal *= 2) <= val)
    power*=2;
  return power*2;
}

void main_render() {
  //Load the font
  TTF_Font *font = TTF_OpenFont("../resource/font.ttf", 10);
  if (font == nullptr) {
    std::cout << "TTF_OpenFont error: " << std::endl;
    return;
  }

  SDL_Color colorFg = {0,0,255};
  SDL_Surface *surface;

  //Render font to a SDL_Surface
  if ((surface = TTF_RenderText_Blended(font, "Hi!", colorFg)) == nullptr) {
    TTF_CloseFont(font);
    std::cout << "TTF_RenderText error: " << std::endl;
    return;
  }

  GLuint texId;

  //Generate OpenGL texture
  glEnable(GL_TEXTURE_2D);
  glGenTextures(1, &texId);
  glBindTexture(GL_TEXTURE_2D, texId);

  //Avoid mipmap filtering
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
  glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

  //Find the first power of two for OpenGL image 
  int w = power_two_floor(surface->w)*2;
  int h = power_two_floor(surface->h)*2;

  //Create a surface to the correct size in RGB format, and copy the old image
  SDL_Surface * s = SDL_CreateRGBSurface(0, w, h, 32, 0x00ff0000,0x0000ff00,0x000000ff,0xff000000);
  SDL_BlitSurface(surface, NULL, s, NULL);

  //Copy the created image into OpenGL format
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, s->pixels);

  //Draw the OpenGL texture as a Quad
  glBegin(GL_QUADS); {
    glTexCoord2d(0, 1); glVertex3f(0,              0,              0);
    glTexCoord2d(1, 1); glVertex3f(0 + surface->w, 0,              0);
    glTexCoord2d(1, 0); glVertex3f(0 + surface->w, 0 + surface->h, 0);
    glTexCoord2d(0, 0); glVertex3f(0,              0 + surface->h, 0); 
  } glEnd();
  glDisable(GL_TEXTURE_2D);

  //Cleanup
  TTF_CloseFont(font);
  SDL_FreeSurface(s);
  SDL_FreeSurface(surface);
  glDeleteTextures(1, &texId);
}