Control Individual Window Brightness

Why does changing window brightness affect the whole display? Is there a way to only change my game's brightness?

SDL's brightness functions affect the entire display because they work by modifying the display's gamma lookup tables, which are hardware-level settings. To adjust brightness only for your game window, you'll need to implement the effect in your rendering pipeline instead. Here's how:

Using SDL_Renderer

If you're using SDL's renderer, you can modify the color of everything you render:

#include <SDL.h>

class BrightnessController {
  SDL_Renderer* Renderer;
  float Brightness{1.0f};

public:
  BrightnessController(SDL_Renderer* R) :
    Renderer{R} {}

  void SetBrightness(float NewBrightness) {
    Brightness = NewBrightness;
    // Convert brightness to SDL's 0-255 range
    Uint8 Value = static_cast<Uint8>(
      Brightness * 255);
    SDL_SetRenderDrawColor(
      Renderer, Value, Value, Value, 255
    );

    // Set blend mode to modulate
    // (multiply) colors
    SDL_SetRenderDrawBlendMode(
      Renderer, SDL_BLENDMODE_MOD
    );
  }

  void Apply() {
    // Create fullscreen overlay with
    // current brightness
    SDL_Rect FullScreen;
    SDL_RenderGetViewport(
      Renderer, &FullScreen);
    SDL_RenderFillRect(Renderer, &FullScreen);
  }
};

int main() {
  SDL_Init(SDL_INIT_VIDEO);

  SDL_Window* Window{
    SDL_CreateWindow(
      "Brightness Demo",
      SDL_WINDOWPOS_UNDEFINED,
      SDL_WINDOWPOS_UNDEFINED,
      800, 600,
      SDL_WINDOW_SHOWN
    )};

  SDL_Renderer* Renderer{
    SDL_CreateRenderer(
      Window, -1, SDL_RENDERER_ACCELERATED
    )};

  BrightnessController Controller{Renderer};

  // Your game loop:
  bool Running{true};
  while (Running) {
    // Clear screen
    SDL_RenderClear(Renderer);

    // Draw your game content here

    // Apply brightness effect
    Controller.SetBrightness(0.5f);
    // 50% brightness
    Controller.Apply();

    // Present the frame
    SDL_RenderPresent(Renderer);
  }

  SDL_DestroyRenderer(Renderer);
  SDL_DestroyWindow(Window);
  SDL_Quit();
  return 0;
}

This approach has several advantages:

  • Only affects your game window
  • Works consistently across all platforms
  • Can be animated smoothly
  • Can be combined with other effects
  • No system permission issues

However, it does require more processing power than using the display's gamma tables, so test performance on your target platforms.

Brightness and Gamma

Learn how to control display brightness and gamma correction using SDL's window management functions

Questions & Answers

Answers are generated by AI models and may not have been reviewed. Be mindful when running any code on your device.

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