在OpenGL中使用SDL_ttf [英] Using SDL_ttf with OpenGL

问题描述

我正在使用OpenGL和SDL在程序中创建一个窗口.

I'm using OpenGL and SDL to create a window in my program.

如何在OpenGL窗口中使用SDL_ttf?

How do I use SDL_ttf with an OpenGL window?

例如，我想加载字体并渲染一些文本.我想使用SDL OpenGL表面绘制文本.

For example I want to load a font and render some text. I want to draw the text using an SDL OpenGL surface.

推荐答案

方法如下:

1. 初始化SDL和SDL_ttf，并使用SDL_SetVideoMode()创建一个窗口.确保您通过了SDL_OPENGL标志.
2. 初始化OpenGL场景(glViewport()，glMatrixMode()等).

3. 使用SDL_ttf渲染文本，例如TTF_RenderUTF8_Blended().渲染函数返回一个SDL_surface，您必须通过将指向数据的指针(surface->pixels)传递给OpenGL以及数据格式，将其转换为OpenGL纹理.像这样:

1. Initialize SDL and SDL_ttf, and create a window using SDL_SetVideoMode(). Make sure you pass the SDL_OPENGL flag.
2. Initialize your OpenGL scene (glViewport(), glMatrixMode() etc.).

3. Render your text with SDL_ttf using e.g. TTF_RenderUTF8_Blended(). The render functions return an SDL_surface, which you have to convert into an OpenGL texture by passing a pointer to the data (surface->pixels) to OpenGL as well as the format of the data. Like this:

colors = surface->format->BytesPerPixel;
if (colors == 4) {   // alpha
    if (surface->format->Rmask == 0x000000ff)
        texture_format = GL_RGBA;
    else
        texture_format = GL_BGRA;
} else {             // no alpha
    if (surface->format->Rmask == 0x000000ff)
        texture_format = GL_RGB;
    else
        texture_format = GL_BGR;
}

glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture); 
glTexImage2D(GL_TEXTURE_2D, 0, colors, surface->w, surface->h, 0,
                    texture_format, GL_UNSIGNED_BYTE, surface->pixels);

然后，您可以使用glBindTexture()等在OpenGL中使用纹理.完成绘制后，请确保调用SDL_GL_SwapBuffers().

Then you can use the texture in OpenGL using glBindTexture() etc. Make sure to call SDL_GL_SwapBuffers() when you're done with drawing.

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