storing_paintbrush_in_accessdb.shtml

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   <TITLE><!-- Section Title -->Database - <!-- Article Title -->Storing "Paint Brush" images in a Access DB</TITLE>
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<!-- Article Title -->Storing "Paint Brush" images in a Access DB
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This article was contributed by <!-- Author Email --><A HREF="mailto:otto@polaris.it"><!-- Author Name -->Luigi Ottoboni</A>.

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This example demonstrates how to store a "Paint Brush" image in a Access DB.
In my code I have created a CDaoRecordset derived class for handling and reading the binary data. 
Class Wizard binds a CLongBinary to the Ole Object field when creating the recordset. 
CLongBinary is difficult to manage, so in the recordset, that is to receive the binary 
data, I bind a CByteArray variable to the field. 
<p>Example : 

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::DoFieldExchange(CDaoFieldExchange* pFX) 

DFX_LongBinary(pFX, _T("[Images]"), m_Images);
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become
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DFX_Binary(pFX, _T("[Images]"), m_Images); 
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In CDAORecordSet the public member "CLongBinary m_Images" become "CByteArray m_Images" 

<p>The function code is : 

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BOOL CBLOBSDlg::ReadFromBLOB(CByteArray & DBArray) 
{ 
  CByteArray Array; 
  Array.Copy( DBArray); 
  // the header of BLOB is OLE stuff like "Paint Brush Application" .... ecc.. 
  // the len is 78 byte ( I do not know for other headers ) 
  int HeaderLen =   78 + sizeof(BITMAPFILEHEADER); 
  Array.RemoveAt( 0, HeaderLen ); // I cut all Headers 
  
  // some BMP information 
  BITMAPINFOHEADER &bmiHeader = *(LPBITMAPINFOHEADER)Array.GetData() ; 
  BITMAPINFO &bmInfo = *(LPBITMAPINFO)Array.GetData() ; 
  
  
  // If bmiHeader.biClrUsed is zero we have to infer the number 
  // of colors from the number of bits used to specify it. 
  int nColors = bmiHeader.biClrUsed ? bmiHeader.biClrUsed : 1 << bmiHeader.biBitCount; 

  LPVOID lpDIBBits; 
  if( bmInfo.bmiHeader.biBitCount > 8 ) 
      lpDIBBits = (LPVOID)((LPDWORD)(bmInfo.bmiColors + bmInfo.bmiHeader.biClrUsed) + 
                        ((bmInfo.bmiHeader.biCompression == BI_BITFIELDS) ? 3 : 0)); 
  else 
      lpDIBBits = (LPVOID)(bmInfo.bmiColors + nColors); 
  

  CClientDC dc(NULL); 
  
  HBITMAP hBmp = CreateDIBitmap( dc.m_hDC,   // handle to device context 
                                 &bmiHeader,     // pointer to bitmap size and format data 
                                 CBM_INIT,       // initialization flag 
                                 lpDIBBits,      // pointer to initialization data 
                                 &bmInfo,        // pointer to bitmap color-format data 
                                 DIB_RGB_COLORS);                // color-data usage 
  
  OleBmp.Attach( hBmp ); 

  Array.RemoveAll(); //Relese Memory 

  return TRUE; 
} 
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Note: 
<p>1: In the example the DB path in "CString CDaoRecorset::GetDefaultDBName()" must be changed!!  
<p>2: This code is for VC++ 5 


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<p>Date Posted: 3 Juli 1998<!-- date here -->



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