#include <windows.h>
#include <math.h>

DECLARE_HANDLE(HDIB);

HDIB WINAPI GammaDIB(HDIB hDIB, double dftGamma /*=1.8*/)
{
   ...
   double dftInvGamma = 1.0 / dftGamma;
   ...
   // Bei RGB-DIB's (24bpp):
   for (uY = 0; uY < uHeight; uY++)
   { // Zeilenschleife
      for (uX = 0; uX < uWidth; uX++)
      { // Spaltenschleife
         *lpDIBDest++ = (BYTE)((255.0 * pow((double)*lpDIBSrc / 255.0, dftInvGamma)) + 0.5);
         lpDIBSrc++;
         *lpDIBDest++ = (BYTE)((255.0 * pow((double)*lpDIBSrc / 255.0, dftInvGamma)) + 0.5);
         lpDIBSrc++;
         *lpDIBDest++ = (BYTE)((255.0 * pow((double)*lpDIBSrc / 255.0, dftInvGamma)) + 0.5);
         lpDIBSrc++;
      }
      // Ausrichtung auf Doppelwortgrenze
   }
   ...
   // Bei indizierten DIB's:
   for (uColor = 0; uColor < uNumColors; uColor++)
   {
      lpBMIDest->bmiColors[uColor].rgbRed =
          (BYTE)((255.0 * pow((double)(lpBMIDest->bmiColors[uColor].rgbRed) / 255.0, dftInvGamma)) + 0.5);
      lpBMIDest->bmiColors[uColor].rgbGreen =
          (BYTE)((255.0 * pow((double)(lpBMIDest->bmiColors[uColor].rgbGreen) / 255.0, dftInvGamma)) + 0.5);
      lpBMIDest->bmiColors[uColor].rgbBlue =
          (BYTE)((255.0 * pow((double)(lpBMIDest->bmiColors[uColor].rgbBlue) / 255.0, dftInvGamma)) + 0.5);
   }
   ...
}