System.Drawing.Bitmap.Bitmap C# (CSharp) Method

        public Bitmap(int width, int height, PixelFormat format)
        {
            imageTransform = new CGAffineTransform(1, 0, 0, -1, 0, height);

            int bitsPerComponent, bytesPerRow;
            CGColorSpace colorSpace;
            CGBitmapFlags bitmapInfo;
            bool premultiplied = false;
            int bitsPerPixel = 0;

            pixelFormat = format;

            // Don't forget to set the Image width and height for size.
            imageSize.Width = width;
            imageSize.Height = height;

            switch (format){
            case PixelFormat.Format32bppPArgb:
            case PixelFormat.DontCare:
                premultiplied = true;
                colorSpace = CGColorSpace.CreateDeviceRGB ();
                bitsPerComponent = 8;
                bitsPerPixel = 32;
                bitmapInfo = CGBitmapFlags.PremultipliedFirst;
                break;
            case PixelFormat.Format32bppArgb:
                colorSpace = CGColorSpace.CreateDeviceRGB ();
                bitsPerComponent = 8;
                bitsPerPixel = 32;
                bitmapInfo = CGBitmapFlags.PremultipliedFirst;
                break;
            case PixelFormat.Format32bppRgb:
                colorSpace = CGColorSpace.CreateDeviceRGB ();
                bitsPerComponent = 8;
                bitsPerPixel = 32;
                bitmapInfo = CGBitmapFlags.NoneSkipLast;
                break;
            case PixelFormat.Format24bppRgb:
                colorSpace = CGColorSpace.CreateDeviceRGB ();
                bitsPerComponent = 8;
                bitsPerPixel = 32;
                bitmapInfo = CGBitmapFlags.NoneSkipLast;
                break;
            default:
                throw new Exception ("Format not supported: " + format);
            }
            bytesPerRow = width * bitsPerPixel/bitsPerComponent;
            int size = bytesPerRow * height;

            bitmapBlock = Marshal.AllocHGlobal (size);
            var bitmap = new CGBitmapContext (bitmapBlock,
                                          width, height,
                                          bitsPerComponent,
                                          bytesPerRow,
                                          colorSpace,
                                          bitmapInfo);
            // This works for now but we need to look into initializing the memory area itself
            // TODO: Look at what we should do if the image does not have alpha channel
            bitmap.ClearRect (new CGRect (0,0,width,height));

            var provider = new CGDataProvider (bitmapBlock, size, true);
            NativeCGImage = new CGImage (width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpace, bitmapInfo, provider, null, false, CGColorRenderingIntent.Default);

            dpiWidth = dpiHeight = ConversionHelpers.MS_DPI;
            physicalDimension.Width = width;
            physicalDimension.Height = height;

            // The physical size may be off on certain implementations.  For instance the dpiWidth and dpiHeight
            // are read using integers in core graphics but in windows it is a float.
            // For example:
            // coregraphics dpiWidth = 24 as integer
            // windows dpiWidth = 24.999935 as float
            // this gives a few pixels difference when calculating the physical size.
            // 256 * 96 / 24 = 1024
            // 256 * 96 / 24.999935 = 983.04
            //
            // https://bugzilla.xamarin.com/show_bug.cgi?id=14365
            // PR: https://github.com/mono/maccore/pull/57
            //

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

            rawFormat = ImageFormat.MemoryBmp;
            pixelFormat = format;
        }