Convert wmf file to emf file with SetWinMetaFileBits api in c++ - c++

Question

I am trying to convert a wmf file to emf file. From what I've learned on Internet, the best solution looks like this.
BYTE* buffer;
HDC hdc = CreateMetaFileA(filename);
HMETAFILE hmf = CloseMetaFile(hdc);
UINT metasize = GetMetaFileBitsEx(hmf, 0, NULL);
buffer = (BYTE*)malloc(metasize);
HENHMETAFILE hEMF = SetWinMetaFileBits(metasize, buffer, NULL, NULL);
The idea here is to use CreateMetaFileA and CloseMetaFile to get HMETAFILE hmf.
Then I tried my code and the weird thing came. The handle hmf always points ??? in memory and the metasize is always 24 with different pictures. And hEMF is always None.
This is really sad because I spend my whole night on figuring out how to make the code work.
I do read a lot of materials including
http://math2.org/luasearch-2/luadist-extract/cdlua-5.2.dist/src/win32/wmf_emf.c
https://www-user.tu-chemnitz.de/~heha/viewzip.cgi/hs/wmfsave.zip/src/wmfsave.cpp?auto=CPP
Can anyone help me here? Thanks.

Answer 1

You need to initialize the METAFILEPICT structure.
Minimal example:
if (hmf) {
DWORD nSize = GetMetaFileBitsEx( hmf, 0, NULL );
if (nSize) {
BYTE *lpvData = new BYTE[nSize];
if (lpvData) {
DWORD dw = GetMetaFileBitsEx( hmf, nSize, lpvData );
if (dw) {
// Fill out a METAFILEPICT structure
mp.mm = MM_ANISOTROPIC;
mp.xExt = 1000;
mp.yExt = 1000;
mp.hMF = NULL;
// Get a reference DC
hDC = GetDC( NULL );
// Make an enhanced metafile from the windows metafile
hemf = SetWinMetaFileBits( nSize, lpvData, hDC, &mp );
// Clean up
ReleaseDC( NULL, hDC );
}
delete[] lpvData;
}
DeleteMetaFile( hmf );
}
My test code:
hdcMeta = CreateMetaFile(NULL);
hBrush = CreateSolidBrush(RGB(0, 0, 255));
Rectangle(hdcMeta, 0, 0, 100, 100);
MoveToEx(hdcMeta, 0, 0, NULL);
LineTo(hdcMeta, 100, 100);
MoveToEx(hdcMeta, 0, 100, NULL);
LineTo(hdcMeta, 100, 0);
SelectObject(hdcMeta, hBrush);
Ellipse(hdcMeta, 20, 20, 80, 80);
hmf = CloseMetaFile(hdcMeta);
UINT nSize = GetMetaFileBitsEx(hmf, 0, NULL);
Debug:
You can see nSize = 114
I suspect that you use CreateMetaFileA and CloseMetaFile to directly load the file name and return a handle to a Windows-format metafile is a wrong way.
Updated:
You can get the handle of WMF file in another way.
#include <windows.h>
#include <iostream>
#include <vector>
#pragma pack(1)
typedef struct tagWIN16RECT
{
WORD left;
WORD top;
WORD right;
WORD bottom;
} WIN16RECT;
typedef struct tagPLACEABLEMETAHEADER
{
DWORD key;
WORD hmf;
WIN16RECT bbox;
WORD inch;
DWORD reserved;
WORD checksum;
} PLACEABLEMETAHEADER;
#pragma pack()
HENHMETAFILE WINAPI ConvertWMFToEWMF(IN LPCWSTR lpszMetaFile)
{
HANDLE hFile = ::CreateFileW(
lpszMetaFile,
GENERIC_READ,
0,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);
if (hFile == NULL || hFile == INVALID_HANDLE_VALUE)
return NULL;
DWORD dwSize = ::GetFileSize(hFile, NULL);
std::vector<BYTE> data(dwSize);
DWORD dwRead;
BOOL bSuccess = ::ReadFile(hFile, &data[0], dwSize, &dwRead, NULL);
::CloseHandle(hFile);
HENHMETAFILE hEnhMetaFile = NULL;
if (bSuccess)
{
PLACEABLEMETAHEADER * hdr = (PLACEABLEMETAHEADER*)&data[0];
int iPlaceableHeaderSize = sizeof(PLACEABLEMETAHEADER);
int iOffset = 0;
if (hdr->key != 0x9AC6CDD7) //not placeable header
{
iOffset = 0; //offset remains zero
}
else
{
iOffset = iPlaceableHeaderSize; //file is offset with placeable windows metafile header
}
hEnhMetaFile = ::SetWinMetaFileBits(data.size(), &data[iOffset], NULL, NULL);
if (NULL == hEnhMetaFile)
{
DWORD dwError = GetLastError();
std::cout << "Failed with error code: " << dwError;
}
else
{
std::cout << "Success! Metafile opened and returned as enhanced metafile";
}
}
return hEnhMetaFile;
}
int main()
{
HENHMETAFILE hEMF = ConvertWMFToEWMF(L"C:\\Users\\strives\\Desktop\\AN00010.WMF");
HENHMETAFILE newHEMF = CopyEnhMetaFile(hEMF, L"new EMF.emf");
return 0;
}

Answer 2

This worked for me
CStatic * m_pictCtrl = (CStatic *)this->GetDlgItem(PICT_STATIC);
LPCSTR file = filePath;
ALDUSMFHEADER aldusmfHeader;
DWORD wBytesRead;
double xOri, xExt, yOri, yExt;
HANDLE fh = CreateFileA(file, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
ReadFile(fh, (void *)&aldusmfHeader, ALDUSMFHEADERSIZE, &wBytesRead, NULL);
xOri = aldusmfHeader.bbox.left;
xExt = aldusmfHeader.bbox.right - xOri;
if (aldusmfHeader.bbox.bottom < aldusmfHeader.bbox.top) {
yOri = aldusmfHeader.bbox.bottom;
yExt = aldusmfHeader.bbox.top - aldusmfHeader.bbox.bottom;
}
else {
yOri = aldusmfHeader.bbox.top;
yExt = aldusmfHeader.bbox.top - aldusmfHeader.bbox.bottom;
}
if (wBytesRead == -1 || wBytesRead < ALDUSMFHEADERSIZE)
{
AfxMessageBox(L" is not a placeable Windows metafile : it cannot be converted into EMF format.");
CloseHandle(fh);
return 0;
}
// Envelope in /100 cm
double Density = static_cast<double>(aldusmfHeader.inch);
double Top = static_cast<double>(aldusmfHeader.bbox.top) / Density;
double RawBottom = static_cast<double>(aldusmfHeader.bbox.bottom) / Density;
double Left = static_cast<double>(aldusmfHeader.bbox.left) / Density;
double RawRight = static_cast<double>(aldusmfHeader.bbox.right) / Density;
// In order to correctly import the EMF metafile into WORD, add one delta
double Bottom, Right, Delta, Rate = 0.1;
if (RawBottom > RawRight)
{
Delta = Rate * RawRight;
Right = RawRight + Delta;
Bottom = Right * RawBottom / RawRight;
}
else
{
Delta = Rate * RawBottom;
Bottom = RawBottom + Delta;
Right = Bottom * RawRight / RawBottom;
}
// Metafile header
SetFilePointer(fh, ALDUSMFHEADERSIZE, NULL, FILE_BEGIN);
METAHEADER mfHeader;
ReadFile(fh, (void *)&mfHeader, sizeof(METAHEADER), &wBytesRead, NULL);
// Allocate memory in order to save into memory bits after the Aldus header in the WMF metafile
// * 2 : 16 bits API
DWORD dwSize = mfHeader.mtSize * 2 * sizeof(BYTE);
BYTE *lpMFBits = (BYTE *)malloc(dwSize);
if (lpMFBits == nullptr)
{
AfxMessageBox(L"nullptr lpmfbits");
//cout << "Not enough memory to convert " << WMFFileName << " into EMF format." << endl;
CloseHandle(fh);
return 0;
}
// Bits after the Aldus header
SetFilePointer(fh, ALDUSMFHEADERSIZE, NULL, FILE_BEGIN);
ReadFile(fh, (void *)lpMFBits, dwSize, &wBytesRead, NULL);
if (wBytesRead == -1)
{
//cout << "Error while reading " << WMFFileName << " : impossible to convert it into EMF format." << endl;
free(lpMFBits);
CloseHandle(fh);
return 0;
}
// Save these bits into a memory enhanced metafile
// The memory enhanced metafile only contains 32 bits API functions : TextOut has been converted into ExtTextOutW,
// CreateFontIndirect has been converted into ExtCreateFontIndirectW, ...
METAFILEPICT MetaFilePict;
MetaFilePict.hMF = NULL;
MetaFilePict.mm = MM_ANISOTROPIC;
double Fact = 10.0 * Density;
MetaFilePict.xExt = static_cast<LONG>(Fact * (Right - Left));
MetaFilePict.yExt = static_cast<LONG>(Fact * (Bottom - Top));
HENHMETAFILE hMemoryEnhMetafile = SetWinMetaFileBits(dwSize, lpMFBits, NULL, &MetaFilePict);
free(lpMFBits);
CloseHandle(fh);
if (m_pictCtrl->GetEnhMetaFile() == NULL)
m_pictCtrl->SetEnhMetaFile(hMemoryEnhMetafile);