How do I rotate a picture in WinForms

Question

I want to have one picture in my application that I can rotate to indicate directions, like wind direction. Or even the time. What code do I use to rotate the picture? Thanks

Update: I am using .NET 2.0, Windows 2000, VS C# 2005

Answer 1

Here's a method you can use to rotate an image in C#:

/// <summary> /// method to rotate an image either clockwise or counter-clockwise /// </summary> /// <param name="img">the image to be rotated</param> /// <param name="rotationAngle">the angle (in degrees). /// NOTE:  /// Positive values will rotate clockwise /// negative values will rotate counter-clockwise /// </param> /// <returns></returns> public static Image RotateImage(Image img, float rotationAngle) {     //create an empty Bitmap image     Bitmap bmp = new Bitmap(img.Width, img.Height);      //turn the Bitmap into a Graphics object     Graphics gfx = Graphics.FromImage(bmp);      //now we set the rotation point to the center of our image     gfx.TranslateTransform((float)bmp.Width / 2, (float)bmp.Height / 2);      //now rotate the image     gfx.RotateTransform(rotationAngle);      gfx.TranslateTransform(-(float)bmp.Width / 2, -(float)bmp.Height / 2);      //set the InterpolationMode to HighQualityBicubic so to ensure a high     //quality image once it is transformed to the specified size     gfx.InterpolationMode = InterpolationMode.HighQualityBicubic;      //now draw our new image onto the graphics object     gfx.DrawImage(img, new Point(0, 0));      //dispose of our Graphics object     gfx.Dispose();      //return the image     return bmp; } 

Answer 2

This is an old thread, and there are several other threads about C# WinForms image rotation, but now that I've come up with my solution I figure this is as good a place to post it as any.

  /// <summary>   /// Method to rotate an Image object. The result can be one of three cases:   /// - upsizeOk = true: output image will be larger than the input, and no clipping occurs    /// - upsizeOk = false & clipOk = true: output same size as input, clipping occurs   /// - upsizeOk = false & clipOk = false: output same size as input, image reduced, no clipping   ///    /// A background color must be specified, and this color will fill the edges that are not    /// occupied by the rotated image. If color = transparent the output image will be 32-bit,    /// otherwise the output image will be 24-bit.   ///    /// Note that this method always returns a new Bitmap object, even if rotation is zero - in    /// which case the returned object is a clone of the input object.    /// </summary>   /// <param name="inputImage">input Image object, is not modified</param>   /// <param name="angleDegrees">angle of rotation, in degrees</param>   /// <param name="upsizeOk">see comments above</param>   /// <param name="clipOk">see comments above, not used if upsizeOk = true</param>   /// <param name="backgroundColor">color to fill exposed parts of the background</param>   /// <returns>new Bitmap object, may be larger than input image</returns>   public static Bitmap RotateImage(Image inputImage, float angleDegrees, bool upsizeOk,                                     bool clipOk, Color backgroundColor)   {      // Test for zero rotation and return a clone of the input image      if (angleDegrees == 0f)         return (Bitmap)inputImage.Clone();       // Set up old and new image dimensions, assuming upsizing not wanted and clipping OK      int oldWidth = inputImage.Width;      int oldHeight = inputImage.Height;      int newWidth = oldWidth;      int newHeight = oldHeight;      float scaleFactor = 1f;       // If upsizing wanted or clipping not OK calculate the size of the resulting bitmap      if (upsizeOk || !clipOk)      {         double angleRadians = angleDegrees * Math.PI / 180d;          double cos = Math.Abs(Math.Cos(angleRadians));         double sin = Math.Abs(Math.Sin(angleRadians));         newWidth = (int)Math.Round(oldWidth * cos + oldHeight * sin);         newHeight = (int)Math.Round(oldWidth * sin + oldHeight * cos);      }       // If upsizing not wanted and clipping not OK need a scaling factor      if (!upsizeOk && !clipOk)      {         scaleFactor = Math.Min((float)oldWidth / newWidth, (float)oldHeight / newHeight);         newWidth = oldWidth;         newHeight = oldHeight;      }       // Create the new bitmap object. If background color is transparent it must be 32-bit,       //  otherwise 24-bit is good enough.      Bitmap newBitmap = new Bitmap(newWidth, newHeight, backgroundColor == Color.Transparent ?                                        PixelFormat.Format32bppArgb : PixelFormat.Format24bppRgb);      newBitmap.SetResolution(inputImage.HorizontalResolution, inputImage.VerticalResolution);       // Create the Graphics object that does the work      using (Graphics graphicsObject = Graphics.FromImage(newBitmap))      {         graphicsObject.InterpolationMode = InterpolationMode.HighQualityBicubic;         graphicsObject.PixelOffsetMode = PixelOffsetMode.HighQuality;         graphicsObject.SmoothingMode = SmoothingMode.HighQuality;          // Fill in the specified background color if necessary         if (backgroundColor != Color.Transparent)            graphicsObject.Clear(backgroundColor);          // Set up the built-in transformation matrix to do the rotation and maybe scaling         graphicsObject.TranslateTransform(newWidth / 2f, newHeight / 2f);          if (scaleFactor != 1f)            graphicsObject.ScaleTransform(scaleFactor, scaleFactor);          graphicsObject.RotateTransform(angleDegrees);         graphicsObject.TranslateTransform(-oldWidth / 2f, -oldHeight / 2f);          // Draw the result          graphicsObject.DrawImage(inputImage, 0, 0);      }       return newBitmap;   } 

This is the result of many sources of inspiration, here at StackOverflow and elsewhere. Naveen's answer on this thread was especially helpful.