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