How To Determine the RGB-Bits-Per Pixel for the Display

MORE INFORMATION

Sample Code

   // Returns the position of the highest order bit in a byte.
   BYTE GetWidth(BYTE b)
   {
     int Count = 0;
				

   }
				

   // GetVideoRGBBitsPerPixel() -
   // 
   // Calculates the number of red, green, and blue bits used in
   // the current display mode.
   // 
   // Return values:
   //   If the display is in a palette mode, rather than an RGB
   //   mode, the function returns FALSE and the RGB bits are not
   //   calculated.
   //   If the display is in an RGB mode then the RGB bits are
   //   derived and the function returns TRUE.
   // 
   BOOL GetVideoRGBBitsPerPixel(LPBYTE lpbRed,   // Bits of red.
                                LPBYTE lpbGreen, // Bits of green.
                                LPBYTE lpbBlue)  // Bits of blue.
   {
     HDC      hdc, hdcMem;
     HBITMAP  hbm;
     COLORREF cr, cr2;
     int      i;
     BYTE     r, g, b;
				

     // Get the display device.
     hdc = GetDC(NULL);
				

     // If the display is in a palette mode, then bail out of the process.
     if (GetDeviceCaps(hdc,  RASTERCAPS) & RC_PALETTE) {
         ReleaseDC(NULL, hdc);
         return FALSE;
     }
				

     // Create a minimal memory surface that has the same
     // properties as the display device.
     hdcMem = CreateCompatibleDC(hdc);
     hbm = CreateCompatibleBitmap(hdc, 1, 1);
				

     // Prepare the surface for drawing.
     SelectObject(hdcMem, hbm);
				

     // Initialize the RGB counters, and start color.
     r = g = b = 0;
     cr2 = 0;
				

     // Loop through shades of gray, and see how many unique
     // red, green, and blue values are represented.
     for (i=1; i<256; i++) {
       cr = SetPixel(hdc, 0, 0, RGB(i, i, i));
				

     // Clean up the objects you created.
     DeleteDC(hdcMem);
     DeleteObject(hbm);
     ReleaseDC(NULL, hdc);
				

     // Get the number of bits needed to represent the
     // number of unique RGB values, and return them.
     *lpbRed   = GetWidth(r);
     *lpbGreen = GetWidth(g);
     *lpbBlue  = GetWidth(b);
				

   }