sdl opengl gamma

sdl2_opengl.cpp

// gcc:
//	 g++ sdl2_opengl.cpp -lSDL2 -lGL -o sdl2_opengl

#include <stdint.h>
#include <stdio.h>

#include <GL/gl.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_opengl.h>

int main( int argc, char **argv )
{
    uint32_t WindowFlags =
        SDL_WINDOW_OPENGL |
        SDL_WINDOW_RESIZABLE |
        SDL_WINDOW_ALLOW_HIGHDPI;

    SDL_GL_SetAttribute( SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG );
    // SDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE );
    SDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_COMPATIBILITY );
    SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
    SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 24 );
    SDL_GL_SetAttribute( SDL_GL_STENCIL_SIZE, 8 );
    SDL_GL_SetAttribute( SDL_GL_CONTEXT_MAJOR_VERSION, 3 );
    SDL_GL_SetAttribute( SDL_GL_CONTEXT_MINOR_VERSION, 2 );
    SDL_GL_SetAttribute( SDL_GL_FRAMEBUFFER_SRGB_CAPABLE, 0 );

    SDL_Window *window = SDL_CreateWindow( "OpenGL Window",
                                           0, 0, 600, 200, WindowFlags );
    SDL_GLContext Context = SDL_GL_CreateContext( window );

    int quit = 0;
    while ( !quit )
    {
        SDL_Event Event;

        while ( SDL_PollEvent( &Event ) )
        {
            if ( Event.type == SDL_KEYDOWN )
            {
                switch ( Event.key.keysym.sym )
                {
                case SDLK_ESCAPE:
                    quit = 1;
                    break;
                default:
                    break;
                }
            }
            else if ( Event.type == SDL_QUIT )
            {
                quit = 1;
            }
        }

        int w, h;
        SDL_GetWindowSize( window, &w, &h );

        glViewport( 0, 0, w, h );
        glClearColor( 1.f, 0.f, 1.f, 0.f );
        glClear( GL_COLOR_BUFFER_BIT );

        glMatrixMode( GL_PROJECTION );
        glLoadIdentity();
        glOrtho( 0.0, 100.0, 100.0, 0.0, -1.0, 1.0 );

        for ( int pass = 0; pass < 2; pass++ )
        {
            float x = 1;
            float y = 5 + 45 * pass;
            float exp = pass ? ( 1.0f / 2.2f ) : 1.0f;

            for ( float c = 0.0f; c <= 1.0f; c += 0.1f )
            {
                float color = pow( c, exp );

                glColor3f( color, color, color );

                glBegin( GL_POLYGON );
                glVertex3f( x, y, 0.0 );
                glVertex3f( x + 8, y, 0.0 );
                glVertex3f( x + 8, y + 40, 0.0 );
                glVertex3f( x, y + 40, 0.0 );
                glEnd();

                x += 10;
            }
        }

        SDL_GL_SwapWindow( window );
    }

    return 0;
}