多次旋轉后的圖像旋轉和質量損失

Question

通過這段代碼，我旋轉了一些圖像，我看到在第二次旋轉后，圖像立即丟失了信息。 我認為問題是由於圖像居中引起的，但事實並非如此。 可能是什么問題呢？

void RotatePicture1(double myangle, TObject *Sender)
{
    XFORM xForm;

    Graphics::TBitmap *SrcBitmap = new Graphics::TBitmap;
    Graphics::TBitmap *DestBitmap = new Graphics::TBitmap;
    SrcBitmap->PixelFormat=pf24bit;
    DestBitmap->PixelFormat=pf24bit;

    TImage *MyImage = (TImage*)Sender;
    SrcBitmap->Width=MyImage->Width;
    SrcBitmap->Height=MyImage->Height;
    DestBitmap->Width=MyImage->Width;
    DestBitmap->Height=MyImage->Height;
    SrcBitmap->Assign(MyImage->Picture->Bitmap);

    SetGraphicsMode(DestBitmap->Canvas->Handle, GM_ADVANCED);

    double fangle = (double)(myangle / 180.0) * M_PI;
    int x0=SrcBitmap->Width/2;
    int y0=SrcBitmap->Height/2;
    double cx=x0 - cos(fangle)*x0 + sin(fangle)*y0;
    double cy=y0 - cos(fangle)*y0 - sin(fangle)*x0;
    xForm.eM11 = (FLOAT) cos(fangle);
    xForm.eM12 = (FLOAT) sin(fangle);
    xForm.eM21 = (FLOAT) -sin(fangle);
    xForm.eM22 = (FLOAT) cos(fangle);
    xForm.eDx  = (FLOAT) cx;
    xForm.eDy  = (FLOAT) cy;

    SetWorldTransform(DestBitmap->Canvas->Handle, &xForm);

    int offset = (MyImage->Width - MyImage->Height) / 2;

    BitBlt(
    DestBitmap->Canvas->Handle, //A handle to the destination device context.
    0,                          //The x-coordinate, of the upper-left corner of the destination rectangle.
    0,                          //The y-coordinate, of the upper-left corner of the destination rectangle.
    SrcBitmap->Width,           //The width, of the source and destination rectangles.
    SrcBitmap->Height,          //The height, of the source and the destination rectangles.
    SrcBitmap->Canvas->Handle,  //A handle to the source device context
    0,                          //The x-coordinate, of the upper-left corner of the source rectangle.
    0,                          //The y-coordinate, of the upper-left corner of the source rectangle.
    SRCCOPY);

    MyImage->Picture->Bitmap->Assign(DestBitmap);

    delete DestBitmap;
    delete SrcBitmap;
}

旋轉前：

幾輪之后：

Answer 1

XFORM.eDx和XFORM.eDy不用於旋轉操作。 WinAPI 輪換對我來說效果很好。