Check Gamma Correction Support

How do I detect if the system supports gamma correction before trying to use it?

SDL doesn't provide a direct way to check gamma support, but we can implement a reliable detection system. Here's a comprehensive approach:

#include <SDL.h>

#include <iostream>

class GammaSupport {
  SDL_Window* Window;
  bool HasGammaSupport{false};
  bool HasBrightnessSupport{false};

public:
  GammaSupport(SDL_Window* W) : Window{W} {
    DetectSupport();
  }

  bool SupportsGamma() const {
    return HasGammaSupport;
  }

  bool SupportsBrightness() const {
    return HasBrightnessSupport;
  }

private:
  void DetectSupport() {
    // Test gamma ramp support
    Uint16 TestRamp[256];
    SDL_CalculateGammaRamp(1.0f, TestRamp);

    // Try to set and then read back gamma values
    if (SDL_SetWindowGammaRamp(
        Window, TestRamp, TestRamp, TestRamp) >=
      0) {
      Uint16 ReadRamp[256];
      if (SDL_GetWindowGammaRamp(
          Window, ReadRamp, nullptr, nullptr) >=
        0) {
        // Compare original and read values
        HasGammaSupport = true;
        for (int i = 0; i < 256; ++i) {
          if (TestRamp[i] != ReadRamp[i]) {
            HasGammaSupport = false;
            break;
          }
        }
      }
    }

    // Test brightness support
    float OriginalBrightness{
      SDL_GetWindowBrightness(Window)};

    if (OriginalBrightness > 0.0f &&
      SDL_SetWindowBrightness(
        Window, OriginalBrightness) >= 0) {
      HasBrightnessSupport = true;
    }

    // Log results
    std::cout << "Display capabilities:\n"
      << "- Gamma Ramps: "
      << (HasGammaSupport
            ? "Supported"
            : "Unsupported")
      << "\n- Brightness: "
      << (HasBrightnessSupport
            ? "Supported"
            : "Unsupported") << '\n';
  }
};

int main() {
  SDL_Init(SDL_INIT_VIDEO);

  SDL_Window* Window{
    SDL_CreateWindow("Gamma Support Test",
                     SDL_WINDOWPOS_UNDEFINED,
                     SDL_WINDOWPOS_UNDEFINED,
                     800, 600,
                     SDL_WINDOW_SHOWN)};

  GammaSupport Support{Window};

  // Use results to determine available features
  if (Support.SupportsGamma()) {
    std::cout << "Using gamma-based effects\n";
  } else if (Support.SupportsBrightness()) {
    std::cout <<
      "Falling back to brightness control\n";
  } else {
    std::cout << "Using shader-based effects\n";
  }

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

This implementation:

  • Tests both gamma ramp and brightness support
  • Verifies that gamma values can be both set and read
  • Provides a clean API for checking capabilities
  • Helps you choose appropriate fallback strategies

Remember to check support during initialization and adapt your rendering strategy accordingly. For example, you might use shader-based effects on systems without gamma support.

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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