为什么StretchBlt缩放后成了这个样子

Question

  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);

Answer 1

CRect rect;
 rect.bottom = 400;
 rect.top = 0;
 rect.left = 0;
 rect.right = 400;
你这里的400,400是图片的大小码？

Answer 2

把上面的IDC_STATIC这个ID修改一下

Answer 3

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);

Answer 4

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