I just wrote my own, if anyone knows how to have qt do this internally or a better way to do this let me know, here's the code in case anyone else is having the same problem:

Qt Code: 
  1. QImage CreateAlphaMask( const QImage& srcImage )
  2. {
  3. 	// QImage one only creates alpha mask for alpha values greater than 128... need it to be all alpha greater than 0
  4.  
  5. 	int nWidth = m_PatchSetImage.width();
  6. 	int nHeight = m_PatchSetImage.height();
  7. 	int nDepth = m_PatchSetImage.depth();
  8.  
  9. 	QImage alphaMask( nWidth, nHeight, QImage::Format_MonoLSB );
  10. 	alphaMask.setColor( 0, 0xffffffff );
  11. 	alphaMask.setColor( 1, 0xff000000 );
  12.  
  13. 	// initialize everything to 0 first
  14. 	memset( alphaMask.bits(), 0, alphaMask.numBytes() );
  15.  
  16. 	switch ( nDepth )
  17. 	{
  18. 	case 32:
  19. 		for ( int y = 0; y < nHeight; ++y )
  20. 		{
  21. 			unsigned char* pMaskData = alphaMask.scanLine( y );
  22. 			unsigned int* pSrcData = (unsigned int*)srcImage.scanLine( y );
  23.  
  24. 			for ( int x = 0; x < nWidth; ++x )
  25. 			{
  26. 				if ( *pSrcData++ >> 24 )
  27. 				{
  28. 					pMaskData[x/8] |= 1 << (x % 8);
  29. 				}
  30. 			}
  31. 		}
  32. 		break;
  33. 	default:
  34. 		// Set mask to all 1's if not 32 bit depth
  35. 		memset( alphaMask.bits(), 0xFF, alphaMask.numBytes() );
  36. 		break;
  37. 	}
  38.  
  39. 	return alphaMask;
  40. }
To copy to clipboard, switch view to plain text mode