I'm a bit stumped here. My problem is that I want to create a polygon with a bitmap in the background, and the bitmap is clipped into the polygon's region. I have succeeded in doing this with this code:
CBitmap* pBitmap = pDoc->GetBitmap(); //bitmap is in my doc
CDC memDC;
memDC.CreateCompatibleDC(pDC);
CPalette* pOldPalette;
CPalette* pPalette = pDoc->GetPalette();
if( pPalette ) {
pOldPalette = pDC->SelectPalette(pPalette, FALSE);
pDC->RealizePalette();
}
DIBSECTION ds;
pBitmap->GetObject( sizeof(DIBSECTION), &ds );
CPoint poly[numpts];
// (assign poly points here)
CRgn rgn1;
rgn1.CreatePolygonRgn( poly, numpts, ALTERNATE );
pDC->SelectClipRgn(&rgn1);
CBitmap* pOldBitmap = memDC.SelectObject(pBitmap);
pDC->StretchBlt( 0, 0, ds.dsBm.bmWidth, ds.dsBm.bmHeight,
&memDC,
0, 0, ds.dsBm.bmWidth, ds.dsBm.bmHeight,
SRCCOPY );
memDC.SelectObject(pOldBitmap);
if( pPalette != NULL ) {
pDC->SelectPalette( pPalette, FALSE );
}
As I said,
this works. Here's the catch though: my objective is to print this, so I need to change the mapmode to MM_TWIPS:
pDC->SetMapMode( MM_TWIPS ); //at the beginning of the draw function
...and likewise, I update my coordinates to match the new mapmode (such as y is negative, and the numbers need to be quite larger). If I don't call SelectClipRgn(), the whole bitmap displays, as it should, but when I do call to clip region, nothing displays at all.
So in conclusion, everything works as intended before I change mapmodes. Has anyone else solved this problem before?
EDIT: Here is the OnDraw() function in its entirety. Note this works if I get rid of the mapmode, and change coordinates back the default coordinate mode.
void CPolyPrintView::OnDraw(CDC* pDC)
{
CPolyPrintDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;
CBitmap* pBitmap = pDoc->GetBitmap();
CDC memDC;
memDC.CreateCompatibleDC(pDC);
pDC->SetMapMode( MM_TWIPS );
if( pBitmap ) {
CPalette* pOldPalette;
CPalette* pPalette = pDoc->GetPalette();
if( pPalette ) {
pOldPalette = pDC->SelectPalette(pPalette, FALSE);
pDC->RealizePalette();
}
DIBSECTION ds;
pBitmap->GetObject( sizeof(DIBSECTION), &ds );
CRgn rgn1;
//plygon region
CPoint poly[5];
poly[0].x = 100;
poly[0].y = -100;
poly[1].x = 250;
poly[1].y = -250;
poly[2].x = 500;
poly[2].y = -150;
poly[3].x = 200;
poly[3].y = -1500;
poly[4].x = 150;
poly[4].y = -1000;
rgn1.CreatePolygonRgn( poly, 5, ALTERNATE );
pDC->SelectClipRgn(&rgn1);
CBitmap* pOldBitmap = memDC.SelectObject(pBitmap);
pDC->StretchBlt( 0, 0, ds.dsBm.bmWidth*10, -ds.dsBm.bmHeight*10,
&memDC,
0, 0, ds.dsBm.bmWidth, ds.dsBm.bmHeight,
SRCCOPY );
memDC.SelectObject(pOldBitmap);
if( pPalette != NULL ) {
pDC->SelectPalette( pPalette, FALSE );
}
}
}
// CFlandersXView printing
BOOL CPolyPrintView::OnPreparePrinting(CPrintInfo* pInfo)
{
pInfo->SetMaxPage(1);
return DoPreparePrinting(pInfo);
}
void CPolyPrintView::OnBeginPrinting(CDC* pDC, CPrintInfo* pInfo)
{
int px, py;
px = pDC->GetDeviceCaps(HORZRES);
py = pDC->GetDeviceCaps(VERTRES);
pInfo->m_rectDraw.SetRect(0, 0, px, py);
}
