using System;

using System.Drawing;

public class Program

{

    public static void Main()

    {

            int w = 300;                                    // Actual width of your image

            int h = 250;                                    // Actual height of your image

            float angle = (float)(Math.PI / 180) * 90f;     // Angle at 90 degrees

            float nw = Math.Abs(w * (float)Math.Cos(angle)) + Math.Abs(h * (float)Math.Sin(angle));

            float nh = Math.Abs(w * (float)Math.Sin(angle)) + Math.Abs(h * (float)Math.Cos(angle));

            Console.WriteLine((int)nw + " by " + (int)nh + " at angle " + (angle / (Math.PI / 180)));

            float displayHeight = nh * 1.15f; // Let's say you want to display your image 15% larger than it is

            Size size = new Size(GetNewWidth((int)nw, (int)nh, (int)displayHeight), (int)(displayHeight / ScreenResolution.Height * 720f)); // 720f = UI.HEIGHT

            // use size in UI.DrawTexture.

    }

    public static int GetNewWidth(int oldWidth, int oldHeight, int newHeight)

    {

            float initialWidth = ((float)oldWidth / (float)oldHeight) * (float)newHeight;

            float percentage = initialWidth / (float)ScreenResolution.Width;

            return (int)(percentage * 1280); // 1280 = UI.WIDTH

    }

    public static int GetNewHeight(int oldWidth, int oldHeight, int newWidth)

    {

            float initialHeight = ((float)oldHeight / (float)oldWidth) * (float)newWidth;

            float percentage = initialHeight / (float)ScreenResolution.Height;

            return (int)(percentage * 720); // 720 = UI.HEIGHT

    }

}

​

public static class ScreenResolution // Game.ScreenResolution

{

    public static int Width = 1920;

    public static int Height = 1080;

}