위의 질문이 너무 방대해서 빌더 예제 소스를 보고 나름 대로 수정해 보고 했는데 잘 안되는 군요.
예제를 보고 아래 소스처럼 코딩을 해봤는데 256비트로 변환 되지않고 15b로 변환 되더라구요!
고수님들 보시고 조언 부탁드립니다. 초보라 힘이 드는 군요ㅠㅠㅠㅠㅠㅠ

void __fastcall TForm1::SB256_conversionClick(TObject *Sender)
{
   TCanvas *tempCanvas = new TCanvas;
   try
   {
    HWND hdc = Image;

    TMyControl *pCtrl = (TMyControl *)Image;
//    tempCanvas->Handle = pCtrl->GetDeviceContext(hdc);
    tempCanvas->Handle = GetDeviceContext(hdc);
    TImage *image2save = new TImage(Form1);
    try
    {
      image2save->Height = Image->Picture->Height;
      image2save->Width = Image->Picture->Width;

      TRect destRect = Rect(0,0,pCtrl->Width,pCtrl->Height);
      TRect sourceRect;
      if (pCtrl->InheritsFrom(__classid(TWinControl)))
        sourceRect = destRect;
      else
        sourceRect = pCtrl->BoundsRect;

      image2save->Canvas->CopyRect(destRect, tempCanvas, sourceRect);
      Image->Canvas->CopyRect(destRect,tempCanvas, sourceRect);

      LogPal SysPal;
      SysPal.lPal.palVersion = 0x300;
      SysPal.lPal.palNumEntries = 256;
      GetSystemPaletteEntries(Image,0,256,SysPal.lPal.palPalEntry);
      image2save->Picture->Bitmap->Palette = CreatePalette(&(SysPal.lPal));

//      image2save->Canvas->Draw(0,0,Image->Canvas);

      if (SaveDialog1->Execute())
        image2save->Picture->SaveToFile(SaveDialog1->FileName);


    }
    __finally
    {
//     delete image2save;
    }
  }
  __finally
  {
    delete tempCanvas;
  }
}