/// <summary>
/// Rotates the bitmap in 90° steps clockwise and returns a new rotated WriteableBitmap.
/// </summary>
/// <param name="bmp">The WriteableBitmap.</param>
/// <param name="angle">The angle in degrees the bitmap should be rotated in 90° steps clockwise.</param>
/// <returns>A new WriteableBitmap that is a rotated version of the input.</returns>
public static WriteableBitmap Rotate(this WriteableBitmap bmp, int angle)
{
using (var context = bmp.GetBitmapContext(ReadWriteMode.ReadOnly))
{
// Use refs for faster access (really important!) speeds up a lot!
var w = context.Width;
var h = context.Height;
var p = context.Pixels;
var i = 0;
WriteableBitmap result = null;
angle %= 360;
if (angle > 0 && angle <= 90)
{
result = BitmapFactory.New(h, w);
using (var destContext = result.GetBitmapContext())
{
var rp = destContext.Pixels;
for (var x = 0; x < w; x++)
{
for (var y = h - 1; y >= 0; y--)
{
var srcInd = y * w + x;
rp[i] = p[srcInd];
i++;
}
}
}
}
else if (angle > 90 && angle <= 180)
{
result = BitmapFactory.New(w, h);
using (var destContext = result.GetBitmapContext())
{
var rp = destContext.Pixels;
for (var y = h - 1; y >= 0; y--)
{
for (var x = w - 1; x >= 0; x--)
{
var srcInd = y * w + x;
rp[i] = p[srcInd];
i++;
}
}
}
}
else if (angle > 180 && angle <= 270)
{
result = BitmapFactory.New(h, w);
using (var destContext = result.GetBitmapContext())
{
var rp = destContext.Pixels;
for (var x = w - 1; x >= 0; x--)
{
for (var y = 0; y < h; y++)
{
var srcInd = y * w + x;
rp[i] = p[srcInd];
i++;
}
}
}
}
else
{
result = WriteableBitmapExtensions.Clone(bmp);
}
return(result);
}
}