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copied!<p>A rotated image may require a larger bitmap to be contained without clipping. A fairly simple way to compute the bounds is to apply the transformation matrix to the corners of the original bounding rectangle. Since the new bitmap is larger, the original image must be drawn such that it is centered, rather than at (0,0).</p> <p>This is demonstrated in the following revision to your code:</p> <pre><code>public static Image RotateImage(Image img, float rotationAngle) { int minx = int.MaxValue, maxx = int.MinValue, miny = int.MaxValue, maxy = int.MinValue; using (Bitmap bmp = new Bitmap(1, 1)) // Dummy bitmap, so we can use TransformPoints to figure out the correct size. { using (Graphics g = Graphics.FromImage(bmp)) { g.TranslateTransform((float)img.Width / 2, (float)img.Height / 2); g.RotateTransform(rotationAngle); g.TranslateTransform(-(float)img.Width / 2, -(float)img.Height / 2); Point[] pts = new Point[4]; pts[0] = new Point(0, 0); pts[1] = new Point(img.Width, 0); pts[2] = new Point(img.Width, img.Height); pts[3] = new Point(0, img.Height); g.TransformPoints(CoordinateSpace.Device, CoordinateSpace.World, pts); foreach (Point pt in pts) { minx = Math.Min(minx, pt.X); maxx = Math.Max(maxx, pt.X); miny = Math.Min(miny, pt.Y); maxy = Math.Max(maxy, pt.Y); } } } Bitmap bmp2 = new Bitmap(maxx - minx, maxy - miny); using (Graphics g = Graphics.FromImage(bmp2)) { g.TranslateTransform((float)bmp2.Width / 2, (float)bmp2.Height / 2); g.RotateTransform(rotationAngle); g.TranslateTransform(-(float)bmp2.Width / 2, -(float)bmp2.Height / 2); g.InterpolationMode = InterpolationMode.HighQualityBicubic; g.DrawImage(img, bmp2.Width / 2 - img.Width / 2, bmp2.Height / 2 - img.Height / 2); } return bmp2; } </code></pre>

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