为什么StretchBlt缩放后成了这个样子

diandian0122 2012-05-20 12:14:19

在内存中画图，然后用StretchBlt画到picturebox上，怎么缩放后有一部分没出来，button1代码如下：

CDC* pDC = GetDlgItem(IDC_STATIC)->GetDC();
CDC memDC;
memDC.CreateCompatibleDC(pDC);
CRect RectPicturebox;
GetDlgItem(IDC_STATIC)->GetClientRect(&RectPicturebox);
CBitmap bmp;
bmp.CreateCompatibleBitmap(pDC,RectPicturebox.Width(),RectPicturebox.Height());
CBitmap *pOldbmp = memDC.SelectObject(&bmp);
CRect rect;
rect.bottom = 400;
rect.top = 0;
rect.left = 0;
rect.right = 400;
memDC.Ellipse(&rect);
pDC->SetStretchBltMode(STRETCH_HALFTONE | STRETCH_ORSCANS);
pDC->StretchBlt(0,0,RectPicturebox.Width(),RectPicturebox.Height(),&memDC,0,0,rect.Width(),rect.Height(),SRCCOPY);

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diandian0122 2012-05-20

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我就是想把源里rect画个大的Rect，然后用StretchBlt缩放到小的RectPctureBox里面，如果把rect弄成和rectpicturebox一样大，不就看不出来缩放的效果了吗

Eleven 2012-05-20

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CDC* pDC = GetDlgItem(IDC_STATIC1)->GetDC();

 CDC memDC;

 memDC.CreateCompatibleDC(pDC);

 CRect RectPicturebox;

 GetDlgItem(IDC_STATIC1)->GetClientRect(&RectPicturebox);

 CBitmap bmp;

 bmp.CreateCompatibleBitmap(pDC,RectPicturebox.Width(),RectPicturebox.Height());

 CBitmap *pOldbmp = memDC.SelectObject(&bmp);

 CRect rect;

 rect.bottom = RectPicturebox.Height();

 rect.top = 0;

 rect.left = 0;

 rect.right = RectPicturebox.Width();

 memDC.Ellipse(&rect);

 pDC->SetStretchBltMode(STRETCH_HALFTONE | STRETCH_ORSCANS);

 pDC->StretchBlt(0,0,RectPicturebox.Width(),RectPicturebox.Height(),&memDC,0,0,rect.Width(),rect.Height(),SRCCOPY);

 memDC.SelectObject(pOldbmp);

 memDC.DeleteDC();

 GetDlgItem(IDC_STATIC1)->ReleaseDC(pDC);