Hey all. I resorted to using LockBits for 2d bitmap image rotation after getting fed up with the slow performance and wacky behavior of both Get/Set Pixel, and RotateTransfom. So here is the code I've come up with, and by my reckoning, it should work perfectly. It doesn't.
private static void InternalRotateImage(Bitmap originalBitmap, Bitmap rotatedBitmap, PointF centerPoint, float theta)
{
BitmapData originalData = originalBitmap.LockBits(
new Rectangle(0, 0, originalBitmap.Width, originalBitmap.Height),
ImageLockMode.ReadOnly,
originalBitmap.PixelFormat);
BitmapData rotatedData = rotatedBitmap.LockBits(
new Rectangle(0, 0, rotatedBitmap.Width, rotatedBitmap.Height),
ImageLockMode.WriteOnly,
rotatedBitmap.PixelFormat);
unsafe
{
byte[,] A = new byte[originalData.Height * 2, originalBitmap.Width * 2];
byte[,] R = new byte[originalData.Height * 2, originalBitmap.Width * 2];
byte[,] G = new byte[originalData.Height * 2, originalBitmap.Width * 2];
byte[,] B = new byte[originalData.Height * 2, originalBitmap.Width * 2];
for (int y = 0; y < originalData.Height; y++)
{
byte* row = (byte*)originalData.Scan0 + (y * originalData.Stride);
for (int x = 0; x < originalData.Width; x++)
{
B[y, x] = row[x * 4];
G[y, x] = row[x * 4 + 1];
R[y, x] = row[x * 4 + 2];
A[y, x] = row[x * 4 + 3];
}
}
for (int y = 0; y < rotatedData.Height; y++)
{
byte* row = (byte*)rotatedData.Scan0 + (y * rotatedData.Stride);
for (int x = 0; x < rotatedData.Width; x++)
{
int newy = (int)Math.Abs((Math.Cos(theta) * (x - centerPoint.X) - Math.Sin(theta) * (y - centerPoint.Y) + centerPoint.X));
int newx = (int)Math.Abs((Math.Sin(theta) * (x - centerPoint.X) + Math.Cos(theta) * (y - centerPoint.Y) + centerPoint.Y));
row[x * 4] = B[newy, newx];
row[x * 4 + 1] = G[newy, newx];
row[x * 4 + 2] = R[newy, newx];
row[x * 4 + 3] = A[newy, newx];
}
}
}
originalBitmap.UnlockBits(originalData);
rotatedBitmap.UnlockBits(rotatedData);
}
Anybody got any ideas? I'm fresh out. Thanks in advance!
EDIT: This is what I ended up using (many thanks to Hans Passant):
private Image RotateImage(Image img, float rotationAngle)
{
Image image = new Bitmap(img.Width * 2, img.Height * 2);
Graphics gfx = Graphics.FromImage(image);
int center = (int)Math.Sqrt(img.Width * img.Width + img.Height * img.Height) / 2;
gfx.TranslateTransform(center, center);
gfx.RotateTransform(rotationAngle);
gfx.DrawImage(img, -img.Width / 2, -img.Height / 2);
return image;
}
It's the same thing as his, just on a per image basis, as opposed to a form.