NGif, Animated GIF Encoder for .NET

int [] GetPixels( Bitmap bitmap )
{
	int [] pixels = new int [ 3 * image.Width * image.Height ];
	int count = 0;
    int tw, th;

    BitmapData data = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadWrite, bitmap.PixelFormat);
    int scanwidth = data.Stride;
    System.IntPtr Scan = data.Scan0;
    int width = bitmap.Width;
    int height = bitmap.Height;

    unsafe
    {
        int offset; // excess pixels at each row, to counter word alignment
        if (bitmap.PixelFormat == PixelFormat.Format32bppArgb ||
            bitmap.PixelFormat == PixelFormat.Format32bppPArgb ||
            bitmap.PixelFormat == PixelFormat.Format32bppRgb)
        {
            offset = scanwidth - bitmap.Width * 4;
        }
        else // assume 24 bits per pixel
            offset = scanwidth - bitmap.Width * 3; 
        int x, y;
        byte colr, colg, colb;
        byte* p = (byte*)(void*)Scan;
        for (y = 0; y < height; y++)
        {
            for (x = 0; x < width; x++)
            {
                pixels[count++] = (int)*(p++);
                pixels[count++] = (int)*(p++);
                pixels[count++] = (int)*(p++);
            }
            p += offset;
        }
    } // End of unsafe
    bitmap.UnlockBits(data);
	return pixels;
}

void SetPixels( int [] pixels )
{
	int count = 0;

    BitmapData data = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height),
        ImageLockMode.ReadWrite, bitmap.PixelFormat);
    int scanwidth = data.Stride;
    System.IntPtr Scan = data.Scan0;
    int width = image.Width;
    int height = image.Height;
    unsafe
    {
        bool fourBytePerPixel = false;
        int offset; // excess pixels at each row, to counter word alignment
        if (bitmap.PixelFormat == PixelFormat.Format32bppArgb ||
            bitmap.PixelFormat == PixelFormat.Format32bppPArgb ||
            bitmap.PixelFormat == PixelFormat.Format32bppRgb)
        {
            offset = scanwidth - bitmap.Width * 4;
            fourBytePerPixel = true;
        }
        else // assume 24 bits per pixel
            offset = scanwidth - bitmap.Width * 3;
        int x, y;
        byte* p = (byte*)(void*)Scan;
        Int32 pixeldata;
        for (y = 0; y < height; y++)
        {
            for (x = 0; x < width; x++)
            {
                pixeldata = pixels[count++];

                *(p++) = (byte)(pixeldata);
                *(p++) = (byte)(pixeldata >> 8);
                *(p++) = (byte)(pixeldata >> 16);
                if (fourBytePerPixel)
                    *(p++) = (byte)(pixeldata >> 24);
            }
            p += offset;
        }
    } // End of unsafe
    bitmap.UnlockBits(data);
}