There is much confusion about bitmap handles (HBITMAP) and device independent bitmaps (DIB). The terms are often interchanged and functions that you would expect to return a DIB, such as CreateDIBitmap, do in fact return a value of type HBITMAP.<\/p>\n
HBITMAP’s are handles to memory objects containing a BITMAP structure followed by palette information and bitmap data and should be processed by ScanBarCodeFromBitmap:<\/p>\n
DIB’s are handles to memory objects that have the same format as a BMP file minus the file header (BITMAPFILEHEADER) and should be processed by ScanBarCodeFromDIB.\u00a0The following MFC C++ code can be used to load a small BMP file into a DIB:<\/p>\n
#include\u00a0<limits.h><\/p>\n
<\/p>\n
HGLOBAL LoadDIB( LPCSTR sBMPFile)<\/p>\n
{<\/p>\n
CFile file;<\/p>\n
<\/p>\n
if( !file.Open( sBMPFile, CFile::modeRead) )<\/p>\n
return\u00a0NULL;<\/p>\n
<\/p>\n
BITMAPFILEHEADER bmfHeader;<\/p>\n
ULONGLONG nFileLen;<\/p>\n
<\/p>\n
nFileLen = file.GetLength();<\/p>\n
<\/p>\n
if\u00a0(nFileLen > UINT_MAX)<\/p>\n
{<\/p>\n
AfxMessageBox(“File is too big to load with a single read”);<\/p>\n
return\u00a0NULL ;<\/p>\n
}<\/p>\n
<\/p>\n
\/\/ Read file header and ignore<\/p>\n
if\u00a0(file.Read((LPSTR)&bmfHeader,\u00a0sizeof(bmfHeader)) !=\u00a0sizeof(bmfHeader))<\/p>\n
return\u00a0NULL;<\/p>\n
<\/p>\n
\/\/ File type should be ‘BM’<\/p>\n
if\u00a0(bmfHeader.bfType != ((WORD) (‘M’\u00a0<< 8) |\u00a0‘B’))\u00a0return\u00a0NULL;<\/p>\n
<\/p>\n
HGLOBAL hDIB = ::GlobalAlloc(GMEM_FIXED, (SIZE_T) nFileLen);<\/p>\n
if\u00a0(hDIB == 0)<\/p>\n
return\u00a0NULL;<\/p>\n
<\/p>\n
\/\/ Read the remainder of the bitmap file.<\/p>\n
if\u00a0(file.Read((LPSTR)hDIB, (UINT) nFileLen –\u00a0sizeof(BITMAPFILEHEADER)) !=<\/p>\n
(UINT) nFileLen –\u00a0sizeof(BITMAPFILEHEADER) )<\/p>\n
{<\/p>\n
::GlobalFree(hDIB);<\/p>\n
return\u00a0NULL;<\/p>\n
}<\/p>\n
<\/p>\n
return\u00a0hDIB;<\/p>\n
}<\/p>\n
<\/p>\n
The following wikipedia article contains a more detailed explanation:\u00a0http:\/\/en.wikipedia.org\/wiki\/BMP_file_format<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
There is much confusion about bitmap handles (HBITMAP) and device independent bitmaps (DIB). The terms are often interchanged and functions that you would expect to return a DIB, such as CreateDIBitmap, do in fact return a value of type HBITMAP. HBITMAP’s are handles to memory objects containing a BITMAP structure followed by palette information and<\/p>\n