[英]Rotating an image using Borland C++ Builder and Windows API functions
我構建了這個示例以快速將圖像旋轉 90 度,但我總是在側面切下圖像。 經過多次測試,不幸的是我仍然不明白問題的原因。
void rotate()
{
Graphics::TBitmap *SrcBitmap = new Graphics::TBitmap;
Graphics::TBitmap *DestBitmap = new Graphics::TBitmap;
SrcBitmap->LoadFromFile("Crayon.bmp");
DestBitmap->Width=SrcBitmap->Width;
DestBitmap->Height=SrcBitmap->Height;
SetGraphicsMode(DestBitmap->Canvas->Handle, GM_ADVANCED);
double myangle = (double)(90.0 / 180.0) * 3.1415926;
int x0=SrcBitmap->Width/2;
int y0=SrcBitmap->Height/2;
double cx=x0 - cos(myangle)*x0 + sin(myangle)*y0;
double cy=y0 - cos(myangle)*y0 - sin(myangle)*x0;
xForm.eM11 = (FLOAT) cos(myangle);
xForm.eM12 = (FLOAT) sin(myangle);
xForm.eM21 = (FLOAT) -sin(myangle);
xForm.eM22 = (FLOAT) cos(myangle);
xForm.eDx = (FLOAT) cx;
xForm.eDy = (FLOAT) cy;
SetWorldTransform(DestBitmap->Canvas->Handle, &xForm);
BitBlt(DestBitmap->Canvas->Handle,
0,
0,
SrcBitmap->Width,
SrcBitmap->Height,
SrcBitmap->Canvas->Handle,
0,
0,
SRCCOPY);
DestBitmap->SaveToFile("Crayon2.bmp");
delete DestBitmap;
delete SrcBitmap;
}
如果旋轉整個圖像,則應翻轉目標圖像的寬度和高度:
DestBitmap->Width = SrcBitmap->Height;
DestBitmap->Height = SrcBitmap->Width;
變換例程根據原始寬度/高度將圖像居中。 我們要調整 x/y 位置以將BitBlt
的起點推到左/上
int offset = (SrcBitmap->Width - SrcBitmap->Height) / 2;
BitBlt(DestBitmap->Canvas->Handle, offset, offset, SrcBitmap->Width, SrcBitmap->Height,
SrcBitmap->Canvas->Handle, 0, 0, SRCCOPY);
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