System.Drawing.GeomUtilities.CreateGeometricTransform C# (CSharp) Method

        internal static CGAffineTransform CreateGeometricTransform(RectangleF rect, Point[] points)
        {
            var p0 = points [0];
            var p1 = points [1];
            var p2 = points [2];

            var width = rect.Width;
            var height = rect.Height;

            float m11 = (p1.X - p0.X) / width;
            float m12 = (p1.Y - p0.Y) / width;
            float m21 = (p2.X - p0.X) / height;
            float m22 = (p2.Y - p0.Y) / height;

            return new CGAffineTransform (m11, m12, m21, m22, p0.X, p0.Y);
        }

        /// <summary>
        /// Draws the specified Image at the specified location and with the specified shape and size.
        ///
        /// The destPoints parameter specifies three points of a parallelogram. The three PointF structures
        /// represent the upper-left, upper-right, and lower-left corners of the parallelogram. The fourth point
        /// is extrapolated from the first three to form a parallelogram.
        ///
        /// The image represented by the image object is scaled and sheared to fit the shape of the parallelogram
        /// specified by the destPoints parameter.
        /// </summary>
        /// <param name="image">Image.</param>
        /// <param name="destPoints">Destination points.</param>
        public void DrawImage(Image image, PointF [] destPoints)
        {
            if (image == null)
            {
                throw new ArgumentNullException("image");
            }
            if (destPoints == null)
            {
                throw new ArgumentNullException("destPoints");
            }
            if (destPoints.Length < 3)
            {
                throw new ArgumentException("Destination points must be an array with a length of 3 or 4. " +
                                            "A length of 3 defines a parallelogram with the upper-left, upper-right, " +
                                            "and lower-left corners. A length of 4 defines a quadrilateral with the " +
                                            "fourth element of the array specifying the lower-right coordinate.");
            }

            // Windows throws a Not Implemented error if the points are more than 3
            if (destPoints.Length > 3)
            {
                throw new NotImplementedException();
            }
            if (image.nativeMetafilePage != null)
            {
                throw new NotImplementedException();
            }

            // create our rectangle.  Offset is 0 because the CreateGeometricTransform bakes our x,y offset in there.
            var rect = new CGRect(0, 0, destPoints [1].X - destPoints [0].X, destPoints [2].Y - destPoints [0].Y);

            // We need to flip our Y axis so the image appears right side up
            var geoTransform = new CGAffineTransform(1, 0, 0, -1, 0, rect.Height);

            //var geott = GeomUtilities.CreateGeometricTransform (rect, destPoints);
            geoTransform.Multiply(GeomUtilities.CreateGeometricTransform(rect, destPoints));

            // Apply our transform to the context
            context.ConcatCTM(geoTransform);

            // now we draw our image.
            context.DrawImage(rect, image.NativeCGImage);

            // Now we revert our image transform from the context
            var revert = CGAffineTransform.CGAffineTransformInvert(geoTransform);

            context.ConcatCTM(revert);
        }