Hello,
I am having trouble figuring out how to successfully write an image to the
SQLite database as a Blob, using C++.
I have an HBITMAP that I would like to be able to store to and retrieve from
the DB. If I understand what I have read correctly, I am supposed to write out
the actual byte data to the DB. Here is what I have done so far.
I pass in pbyBitmap as the bmBytes parameter to this function:
ImportPageImage(CPage* pPage, BYTE* bmBytes, DWORD bmSize), which calls the
code below. . .
//prepare query
static const WCHAR tblInsertBlob[] = _T("Insert into [tblBlob] ([Data]) values
(?)");
SQL_HANDLE blobHandle = m_pSqliteDB->PrepareQuery16(tblInsertBlob); //calls
sqlite3_prepare16()
//bind blob
m_pSqliteDB->BindBlob(blobHandle, 1, (void *)bmBytes, bmSize); //calls
sqlite3_bind_blob (bmBytes is the pData param)
Then I call StepQuery to execute it, and then I close the query.
sqlite3_bind_blob() returns SQLITE_OK when I run it, so it does not seem to be
encountering an error there.
Something apparently gets written to the database, but it does not seem to be
correct. When I try to retrieve and display my image, it is all black (which is
how bitmaps look when there is no data).
I think that the problem is coming from writing the BLOB to the database, but I
am not entirely sure. Just in case it is getting written properly and I am not
reading it from the database correctly, I will show you how I pulled it from
the DB.
//prepare blob
sqlite3_blob* pBlob = NULL;
sqlite3_blob_open(m_sqliteDB, "main", "tblBlob", "Data", iBlobID, FALSE,
&pBlob);
BLOB_HANDLE hBlob = pBlob;
int size = sqlite3_blob_bytes(hBlob); //works correctly, returns 998058
BYTE* pBuffer = g_MemMgr.AllocDataBuffer(size);
sqlite3_blob_read(hBlob, pBuffer, size, 0); //returns SQLITE_OK
sqlite3_blob_close(hBlob);
I then try to make a bitmap out of the bytes in pBuffer, but when I do, it
turns out all black (as I mentioned earlier).
Do I have the concept correct? And if so, what part of my current code should I
change to be able to use my DB to store image data?
Thanks a lot.
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