🚀 go-pugleaf

Hi Fernando,
> How can I convert gif/jpg to bmp?

The following function uses the IPicture interface to convert a GIF or JPEG
to a bitmap; it returns a TBitmap object which you can dump to a file via
TBitmap::SaveToFile()...

#include <ole2.h>
#include <olectl.h>
#include <memory>
Graphics::TBitmap* LoadImageFromFile(
   AnsiString filename
  )
{
  // open the file for shared reading
  HANDLE const hFile = CreateFile(
    filename.c_str(), GENERIC_READ, FILE_SHARE_READ, NULL,
    OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL
    );
  if (hFile == INVALID_HANDLE_VALUE)
  {
    throw EWin32Error("Error opening file.");
  }

  // allocate a global memory object of the file's size
  DWORD const dwSize = GetFileSize(hFile, NULL);
  HGLOBAL hData = GlobalAlloc(GMEM_MOVEABLE, dwSize);
  if (hData == NULL)
  {
    CloseHandle(hFile);
    throw EWin32Error("Error allocating memory.");
  }

  // grab a pointer to the memory
  LPVOID pData = GlobalLock(hData);
  if (pData == NULL)
  {
    GlobalFree(hData);
    CloseHandle(hFile);
    throw EWin32Error("Error accessing memory.");
  }

  // read the data from the file
  DWORD dwRead = 0;
  bool read_ok = ReadFile(hFile, pData, dwSize, &dwRead, NULL);
  if (!read_ok  || (dwRead != dwSize))
  {
    GlobalUnlock(hData);
    GlobalFree(hData);
    CloseHandle(hFile);
    throw EWin32Error("Error reading file.");
  }

  // clean up
  GlobalUnlock(hData);
  CloseHandle(hFile);

  // create an IStream object on hData
  IStream* pStream;
  HRESULT hRes = CreateStreamOnHGlobal(hData, false, &pStream);
  if (FAILED(hRes))
  {
    GlobalFree(hData);
    throw EWin32Error("Failed to create IStream.");
  }

  // load the picture (create an IPicture object)
  IPicture* pPicture;
  hRes = OleLoadPicture(
    pStream, 0, false, IID_IPicture,
    reinterpret_cast<void**>(&pPicture)
    );
  if (FAILED(hRes))
  {
    pStream->Release();
    GlobalFree(hData);
    throw EWin32Error("Failed to create IPicture.");
  }

  // grab a handle to the Picture's palette, if present
  HPALETTE hPal = NULL;
  pPicture->get_hPal(reinterpret_cast<OLE_HANDLE*>(hPal));
  if (hPal != NULL)
  {
    int const num_entries =
      GetPaletteEntries(hPal, 0, 0, NULL);
    long const size = sizeof(LOGPALETTE) +
      (num_entries - 1) * sizeof(PALETTEENTRY);

    // copy the palette (because IPicture owns it)
    LPLOGPALETTE pLogPal =
      reinterpret_cast<LPLOGPALETTE>(GlobalAlloc(GPTR, size));
    if (pLogPal != NULL)
    {
      int const num_got = GetPaletteEntries(
        hPal, 0, num_entries, pLogPal->palPalEntry
        );
      pLogPal->palVersion = 0x300;
      pLogPal->palNumEntries = num_got;
      hPal = CreatePalette(pLogPal);
      GlobalFree(pLogPal);
    }
  }

  // retrieve the width and height of the picture
  SIZE SHiMetric = {0, 0};
  pPicture->get_Width(&SHiMetric.cx);
  pPicture->get_Height(&SHiMetric.cy);

  // convert HIMETRIC units to pixels
  HDC hScreenDC = GetDC(NULL);
  int const width = MulDiv(
    SHiMetric.cx, GetDeviceCaps(hScreenDC, LOGPIXELSX), 2540
    );
  int const height = MulDiv(
    SHiMetric.cy, GetDeviceCaps(hScreenDC, LOGPIXELSY), 2540
    );
  ReleaseDC(NULL, hScreenDC);

  // create a TBitmap object
  std::auto_ptr<Graphics::TBitmap> Bitmap(new Graphics::TBitmap());
  try
  {
    // set the bitmap's attributes
    Bitmap->PixelFormat = pf24bit;
    Bitmap->Width = width;
    Bitmap->Height = height;

    // grab a handle to the bitmap's memory DC
    HDC const hMemDC = Bitmap->Canvas->Handle;

    // associate the palette (if present) with the bitmap's DC
    HPALETTE hOldPal = NULL;
    if (hPal != NULL)
    {
      Bitmap->Palette = hPal;
      hOldPal = SelectPalette(hMemDC, hPal, false);
      RealizePalette(hMemDC);
    }

    // render the picture to the memory DC
    pPicture->Render(
      hMemDC, 0, 0, width, height, 0, SHiMetric.cy,
      SHiMetric.cx, -SHiMetric.cy, NULL
      );

    // clean up
    if (hOldPal != NULL)
    {
      SelectPalette(hMemDC, hOldPal, false);
    }
    pPicture->Release();
    pStream->Release();
    GlobalFree(hData);
  }
  catch (...)
  {
    // clean up
    pPicture->Release();
    pStream->Release();
    GlobalFree(hData);
    throw;
  }
  
  // retun the bitmap (caller assumes ownership)
  return Bitmap.release();
}  

HTH,
-- 
Damon (TeamB)
BCBCAQ--http://bcbcaq.bytamin-c.com