Control Individual Window Brightness

1#include <SDL.h>
2
3class BrightnessController {
4  SDL_Renderer* Renderer;
5  float Brightness{1.0f};
6
7public:
8  BrightnessController(SDL_Renderer* R) :
9    Renderer{R} {}
10
11  void SetBrightness(float NewBrightness) {
12    Brightness = NewBrightness;
13    // Convert brightness to SDL's 0-255 range
14    Uint8 Value = static_cast<Uint8>(
15      Brightness * 255);
16    SDL_SetRenderDrawColor(
17      Renderer, Value, Value, Value, 255
18    );
19
20    // Set blend mode to modulate
21    // (multiply) colors
22    SDL_SetRenderDrawBlendMode(
23      Renderer, SDL_BLENDMODE_MOD
24    );
25  }
26
27  void Apply() {
28    // Create fullscreen overlay with
29    // current brightness
30    SDL_Rect FullScreen;
31    SDL_RenderGetViewport(
32      Renderer, &FullScreen);
33    SDL_RenderFillRect(Renderer, &FullScreen);
34  }
35};
36
37int main() {
38  SDL_Init(SDL_INIT_VIDEO);
39
40  SDL_Window* Window{
41    SDL_CreateWindow(
42      "Brightness Demo",
43      SDL_WINDOWPOS_UNDEFINED,
44      SDL_WINDOWPOS_UNDEFINED,
45      800, 600,
46      SDL_WINDOW_SHOWN
47    )};
48
49  SDL_Renderer* Renderer{
50    SDL_CreateRenderer(
51      Window, -1, SDL_RENDERER_ACCELERATED
52    )};
53
54  BrightnessController Controller{Renderer};
55
56  // Your game loop:
57  bool Running{true};
58  while (Running) {
59    // Clear screen
60    SDL_RenderClear(Renderer);
61
62    // Draw your game content here
63
64    // Apply brightness effect
65    Controller.SetBrightness(0.5f);
66    // 50% brightness
67    Controller.Apply();
68
69    // Present the frame
70    SDL_RenderPresent(Renderer);
71  }
72
73  SDL_DestroyRenderer(Renderer);
74  SDL_DestroyWindow(Window);
75  SDL_Quit();
76  return 0;
77}