gl-preferred-format.c

// clang -O3 gl-preferred-format.c -o gl-preferred-format -lGL -lglut

#include <stdio.h>

#define GL_GLEXT_PROTOTYPES

#if defined(__GNUC__) && (defined(__APPLE_CPP__) || defined(__APPLE_CC__))
 #include <GLUT/glut.h>
#else
 #include <GL/glut.h>
#endif

int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_ALPHA);
    int win = glutCreateWindow(argv[0]);

    const GLubyte *name     =  glGetString(GL_VENDOR);
    const GLubyte *renderer =  glGetString(GL_RENDERER);
    const GLubyte *version  =  glGetString(GL_VERSION);

    printf("Vendor: %s\nRenderer: %s\nVersion: %s\n", name, renderer, version);

    printf("Preferred formats for GL_RGB8:\n");

    GLint preferred_format, preferred_type;
    glGetInternalformativ(GL_TEXTURE_2D, GL_RGB8, GL_TEXTURE_IMAGE_FORMAT, 1, &preferred_format);
    glGetInternalformativ(GL_TEXTURE_2D, GL_RGB8, GL_TEXTURE_IMAGE_TYPE, 1, &preferred_type);
    printf("  0x%x / 0x%x  -- upload\n", preferred_format, preferred_type);

    glGetInternalformativ(GL_TEXTURE_2D, GL_RGB8, GL_READ_PIXELS_FORMAT, 1, &preferred_format);
    glGetInternalformativ(GL_TEXTURE_2D, GL_RGB8, GL_READ_PIXELS_TYPE, 1, &preferred_type);
    printf("  0x%x / 0x%x  -- read\n", preferred_format, preferred_type);

    glGetInternalformativ(GL_TEXTURE_2D, GL_RGB8, GL_GET_TEXTURE_IMAGE_FORMAT, 1, &preferred_format);
    glGetInternalformativ(GL_TEXTURE_2D, GL_RGB8, GL_GET_TEXTURE_IMAGE_TYPE, 1, &preferred_type);
    printf("  0x%x / 0x%x  -- get texture\n", preferred_format, preferred_type);

    printf("Preferred formats for GL_RGBA8:\n");

    glGetInternalformativ(GL_TEXTURE_2D, GL_RGBA8, GL_TEXTURE_IMAGE_FORMAT, 1, &preferred_format);
    glGetInternalformativ(GL_TEXTURE_2D, GL_RGBA8, GL_TEXTURE_IMAGE_TYPE, 1, &preferred_type);
    printf("  0x%x / 0x%x  -- upload\n", preferred_format, preferred_type);

    glGetInternalformativ(GL_TEXTURE_2D, GL_RGBA8, GL_READ_PIXELS_FORMAT, 1, &preferred_format);
    glGetInternalformativ(GL_TEXTURE_2D, GL_RGBA8, GL_READ_PIXELS_TYPE, 1, &preferred_type);
    printf("  0x%x / 0x%x  -- read\n", preferred_format, preferred_type);

    glGetInternalformativ(GL_TEXTURE_2D, GL_RGBA8, GL_GET_TEXTURE_IMAGE_FORMAT, 1, &preferred_format);
    glGetInternalformativ(GL_TEXTURE_2D, GL_RGBA8, GL_GET_TEXTURE_IMAGE_TYPE, 1, &preferred_type);
    printf("  0x%x / 0x%x  -- get texture\n", preferred_format, preferred_type);

    glutDestroyWindow(win);
    return 0;
}