public void add_pixels4(byte[] pixels, int pixel_offset, short[] block, int block_offset, int line_size)
{
int i;
for (i = 0; i < 4; i++)
{
Inc(ref pixels[pixel_offset + 0], block[block_offset + 0]);
Inc(ref pixels[pixel_offset + 1], block[block_offset + 1]);
Inc(ref pixels[pixel_offset + 2], block[block_offset + 2]);
Inc(ref pixels[pixel_offset + 3], block[block_offset + 3]);
pixel_offset += line_size;
block_offset += 4;
}
}