if ( abs( dx ) < in_x_range && abs( dy ) < in_y_range )
{
// We're in the input range for this row.
- in_ptr = in_line + ( dx >> 1 ) * 4 - 2 * ( x & 1 );
+ in_ptr = in_line + ( dx >> 1 ) * 4 + 2 * ( x & 1 );
*out_ptr ++ = *in_ptr ++;
*out_ptr ++ = *in_ptr ++;
}