virtual void set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
virtual bool needs_srgb_primaries() const { return false; }
virtual void set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
virtual bool needs_srgb_primaries() const { return false; }