[golang]图片按中心旋转后，新图的左顶点位置的偏移量

1 前言

图片按中心旋转后，新图的左顶点位置的偏移量

2 代码

func OffsetXYAfterRotationCore(W, H, L, T, Angle float64) (x, y float64) {

   var DX, DY, X, Y float64

   AngleRad := Angle * math.Pi / 180

   SinX := math.Sin(AngleRad)

   CosX := math.Cos(AngleRad)

   //0<=Angle <=90

   if Angle >= 0 && Angle <= 90 {

      DX = SinX * H

      DY = 0

      X = L - DX

      Y = T - DY

      //fmt.Println("At last Angle,X,Y,DX,DY=", Angle, X, Y, DX, DY)

   } else if Angle > 90 && Angle <= 180 {

      //90<=Angle <=180

      //SinX2 := math.Sin((180 - Angle) )

      //CosX2 := math.Cos((180 - Angle) )

      SinX2 := SinX

      CosX2 := -CosX

      DX = SinX2*H + W*CosX2

      DY = H * CosX2

      X = L - DX

      Y = T - DY

      //fmt.Println("At last Angle,X,Y,DX,DY=", Angle, X, Y, DX, DY)

   } else if Angle > 180 && Angle <= 270 {

      //SinX2 := math.Sin((270 - Angle))

      //CosX2 := math.Cos((270 - Angle))

      SinX2 := -CosX

      CosX2 := -SinX

      DX = SinX2 * W

      DY = CosX2*W + SinX2*H

      X = L - DX

      Y = T - DY

      //fmt.Println("At last Angle,X,Y,DX,DY=", Angle, X, Y, DX, DY)

   } else {

      //SinX2 := math.Sin((360 - Angle))

      SinX2 := -SinX

      DX = 0

      DY = SinX2 * W

      X = L - DX

      Y = T - DY

      //fmt.Println("At last Angle,X,Y,DX,DY=", Angle, X, Y, DX, DY)

   }

   x = X

   y = Y

   return

}

3 效果图

1981x325

1878x1272