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

        internal static CGAffineTransform CreateRotateFlipTransform(ref int width, ref int height, float angle, bool flipX, bool flipY)
        {
            float rotateX    =  (float)Math.Abs ( Math.Cos ( angle.ToRadians() ) );
            float rotateY    =  (float)Math.Abs ( Math.Sin ( angle.ToRadians() ) );

            float deltaWidth    =  width * rotateX + height  * rotateY;
            float deltaHeight    =  width * rotateY + height  * rotateX;

            CGAffineTransform rotateFlipTransform = CGAffineTransform.MakeTranslation(flipX?-deltaWidth:0.0f,flipY?-deltaHeight:0.0f);
            rotateFlipTransform.Multiply(CGAffineTransform.MakeScale(flipX?-1.0f:1.0f,flipY?-1.0f: 1.0f));

            if (0.0f != angle)
            {
                var rot	=  CGAffineTransform.MakeTranslation(-deltaHeight*0.5f,-deltaWidth*0.5f);
                rot.Rotate(angle.ToRadians());
                rot.Translate(deltaWidth*0.5f,deltaHeight*0.5f);

                rotateFlipTransform = CGAffineTransform.Multiply (rot, rotateFlipTransform);
            }

            width = (int)deltaWidth;
            height = (int)deltaHeight;

            return rotateFlipTransform;
        }

        internal new void RotateFlip(RotateFlipType rotateFlipType)
        {
            CGAffineTransform rotateFlip = CGAffineTransform.MakeIdentity();

            int width, height;

            width  = (int)NativeCGImage.Width;
            height = (int)NativeCGImage.Height;

            switch (rotateFlipType)
            {
            //			case RotateFlipType.RotateNoneFlipNone:
            //			//case RotateFlipType.Rotate180FlipXY:
            //				rotateFlip = GeomUtilities.CreateRotateFlipTransform (b.Width, b.Height, 0, false, false);
            //				break;
            case RotateFlipType.Rotate90FlipNone:
                //case RotateFlipType.Rotate270FlipXY:
                rotateFlip = GeomUtilities.CreateRotateFlipTransform(ref width, ref height, 90, false, false);
                break;

            case RotateFlipType.Rotate180FlipNone:
                //case RotateFlipType.RotateNoneFlipXY:
                rotateFlip = GeomUtilities.CreateRotateFlipTransform(ref width, ref height, 0, true, true);
                break;

            case RotateFlipType.Rotate270FlipNone:
                //case RotateFlipType.Rotate90FlipXY:
                rotateFlip = GeomUtilities.CreateRotateFlipTransform(ref width, ref height, 270, false, false);
                break;

            case RotateFlipType.RotateNoneFlipX:
                //case RotateFlipType.Rotate180FlipY:
                rotateFlip = GeomUtilities.CreateRotateFlipTransform(ref width, ref height, 0, true, false);
                break;

            case RotateFlipType.Rotate90FlipX:
                //case RotateFlipType.Rotate270FlipY:
                rotateFlip = GeomUtilities.CreateRotateFlipTransform(ref width, ref height, 90, true, false);
                break;

            case RotateFlipType.Rotate180FlipX:
                //case RotateFlipType.RotateNoneFlipY:
                rotateFlip = GeomUtilities.CreateRotateFlipTransform(ref width, ref height, 0, false, true);
                break;

            case RotateFlipType.Rotate270FlipX:
                //case RotateFlipType.Rotate90FlipY:
                rotateFlip = GeomUtilities.CreateRotateFlipTransform(ref width, ref height, 270, true, false);
                break;
            }

            var bytesPerRow      = (width * (int)NativeCGImage.BitsPerPixel + 7) / 8;
            var newBitmapBlock   = Marshal.AllocHGlobal(height * bytesPerRow);
            var newBitmapContext = new CGBitmapContext(newBitmapBlock, width, height, NativeCGImage.BitsPerComponent, bytesPerRow, NativeCGImage.ColorSpace, NativeCGImage.AlphaInfo);

            newBitmapContext.ConcatCTM(rotateFlip);
            newBitmapContext.DrawImage(new CGRect(0, 0, NativeCGImage.Width, NativeCGImage.Height), NativeCGImage);
            newBitmapContext.Flush();

            // If the width or height is not the seme we need to switch the dpiHeight and dpiWidth
            // We should be able to get around this with set resolution later.
            if (NativeCGImage.Width != width || NativeCGImage.Height != height)
            {
                var temp = dpiWidth;
                dpiHeight = dpiWidth;
                dpiWidth  = temp;
            }

            physicalDimension.Width  = (float)width;
            physicalDimension.Height = (float)height;

            physicalSize         = new SizeF(physicalDimension.Width, physicalDimension.Height);
            physicalSize.Width  *= ConversionHelpers.MS_DPI / dpiWidth;
            physicalSize.Height *= ConversionHelpers.MS_DPI / dpiHeight;

            // In windows the RawFormat is changed to MemoryBmp to show that the image has changed.
            rawFormat = ImageFormat.MemoryBmp;

            // Set our transform for this image for the new height
            imageTransform = new CGAffineTransform(1, 0, 0, -1, 0, height);

            // bitmapBlock is owned by dataProvider and freed implicitly
            if (dataProvider != null)
            {
                dataProvider.Dispose();
            }

            if (cachedContext != null)
            {
                cachedContext.Dispose();
            }
            NativeCGImage.Dispose();

            this.bitmapBlock   = newBitmapBlock;
            this.dataProvider  = new CGDataProvider(bitmapBlock, height * bytesPerRow);
            this.NativeCGImage = newBitmapContext.ToImage();
            this.cachedContext = newBitmapContext;
            this.imageSource   = null;

            // update the cached size
            imageSize.Width  = this.Width;
            imageSize.Height = this.Height;
        }