Copy tiles from one tiff to another (4-band)

Question

I'm trying to simply use an offset to select tiles from one tiff image and write them to another image. I am using libtiff.net. Instead of each pixel having an ARGB value, there is one pixel that is alpha, then the pixel to the right of that is a red pixel, the one to the right of that is green and of course the one to the right of that is blue. I need to store those 4 pixels in one and something is happening along the way. Can you see anything wrong with this logic?

using (Tiff output = Tiff.Open(@"C:\base.tif", "w"))
{
    if (output == null)
    {
        System.Console.Error.WriteLine("Could not open outgoing image");
        return;
    }


    // We need to know the width and the height before we can malloc
    int[] raster = new int[tileWidth * tileHeight];

    // Write the tiff tags to the file
    output.SetField(TiffTag.IMAGEWIDTH, 1024);
    output.SetField(TiffTag.IMAGELENGTH, 1024);
    output.SetField(TiffTag.TILEWIDTH, 256);
    output.SetField(TiffTag.TILELENGTH, 256);
    output.SetField(TiffTag.COMPRESSION, Compression.DEFLATE);
    output.SetField(TiffTag.PLANARCONFIG, PlanarConfig.CONTIG);
    output.SetField(TiffTag.PHOTOMETRIC, Photometric.RGB);
    output.SetField(TiffTag.BITSPERSAMPLE, 8);
    output.SetField(TiffTag.SAMPLESPERPIXEL, numOfBands);

    byte[] inputBuffer = new byte[tileWidth * tileHeight * numOfBands];

    // loop through every tile column
    for (int x = 0; x < 1024 / tileWidth; x++)
    {
        // loop through every tile row in the current column
        for (int y = 0; y < 1024 / tileHeight; y++)
        {
            image.ReadRGBATile((x + xOffset) * tileWidth, (y + yOffset) * tileHeight, raster);
            Tiff.IntsToByteArray(raster, 0, raster.Length, inputBuffer, 0);
            output.WriteEncodedTile(getTileIndex(x, y, 1024 / tileWidth), inputBuffer, 0, raster.Length);
        }
    }
}