旋转位图并跟踪新图像上的位置 C#

Question

如果我旋转位图并想要跟踪原始图像上翻译到新图像上的点，我将如何实现这一点。我本质上想知道原始图像的右上角在新的旋转和扩展图像上的位置，以便我可以在正确的位置绘制到图形表面。我使用以下代码来旋转位图（最初取自另一篇文章）。

      public static Bitmap RotateImage(Bitmap origBmp, float angle)
      {
         Matrix matrix = new Matrix();
         matrix.Translate(origBmp.Width / -2, origBmp.Height / -2, MatrixOrder.Append);
         matrix.RotateAt(angle, new Point(0, 0), MatrixOrder.Append);

         using (GraphicsPath graphicsPath = new GraphicsPath())
         {
            // Transform image points by rotation matrix
            graphicsPath.AddPolygon(new Point[]
            {
               new Point(0, 0),
               new Point(origBmp.Width, 0),
               new Point(0, origBmp.Height)
            });

            graphicsPath.Transform(matrix);
            PointF[] pts = graphicsPath.PathPoints;

            Rectangle boundingBox = BoundingBox(origBmp, matrix);
            Bitmap bmpDest = new Bitmap(boundingBox.Width, boundingBox.Height);

            using (Graphics graphicsDest = Graphics.FromImage(bmpDest))
            {
               Matrix matrixDest = new Matrix();
               matrixDest.Translate(bmpDest.Width / 2, bmpDest.Height / 2, MatrixOrder.Append);
               graphicsDest.Transform = matrixDest;
               graphicsDest.DrawImage(origBmp, pts);
            }

            return bmpDest;
         }
      }

      private static Rectangle BoundingBox(
         Image img,
         Matrix matrix)
      {
         GraphicsUnit gu = new GraphicsUnit();
         Rectangle imgRect = Rectangle.Round(img.GetBounds(ref gu));

         // Transform the four points of the image, to get the resized bounding box.
         Point topLeft = new Point(imgRect.Left, imgRect.Top);
         Point topRight = new Point(imgRect.Right, imgRect.Top);
         Point bottomRight = new Point(imgRect.Right, imgRect.Bottom);
         Point bottomLeft = new Point(imgRect.Left, imgRect.Bottom);

         Point[] points = new Point[]
         {
            topLeft,
            topRight,
            bottomRight,
            bottomLeft
         };

         GraphicsPath graphicsPath = new GraphicsPath(
            points,
            new byte[]
            {
               (byte)PathPointType.Start,
               (byte)PathPointType.Line,
               (byte)PathPointType.Line,
               (byte)PathPointType.Line
            });

         graphicsPath.Transform(matrix);
         return Rectangle.Round(graphicsPath.GetBounds());
      }

具体来说，我正在尝试在正确的位置和旋转处绘制风“倒钩”。

我尝试使用相同的翻译方法来翻译原始图像上的点，但没有成功。

Answer 1

如果我旋转位图并想要跟踪原始位图上的点 在新图像上翻译的图像，我将如何实现这一目标。

/// <summary>
/// Target is starting point; center is pivot; angle is rotation. 
/// Returns rotated point (e.g. new cp).
/// </summary>
internal static Point RotatePoint( Point target, Point center, double angle ) {

   RotateTransform t = new RotateTransform();
   t.CenterX = center.X;
   t.CenterY = center.Y;
   t.Angle = angle;

   Point result = t.TransformPoint( target );

   return result;
}