There have been thread before about doing fast alpha blends with GIL views. Here is what I settled with. boost::gil::gray8c_view_t grayview = boost::gil::interleaved_view(width,height,(gray8_pixel_t*)buffer,width); copy_view(pixel(0,0,0),grayview,someview); struct alpha_blend { short alpha; alpha_blend(short alpha) : alpha(alpha){} template <typename T> void operator()(T& dst, const T src) { dst = ((dst + 1) * alpha >> 8) - ((src + 1) * alpha >> 8) + src; } }; template <typename pixel_t, typename grayview_t, typename view_t> inline void copy_view(pixel_t pixel, const grayview_t& grayview, const view_t& view) { using namespace boost::gil; BOOST_ASSERT(grayview.width() == view.width()); typedef typename view_t::x_iterator x_iterator_t; typedef typename grayview_t::x_iterator x_iterator2_t; for (int y = 0; y < view.height(); ++y) { x_iterator_t it_view = view.row_begin(y); x_iterator2_t it_gray = grayview.row_begin(y); for (int x = 0; x < view.width(); ++x) { pixel_t dst = pixel; static_for_each(dst, it_view[x], alpha_blend(it_gray[x])); it_view[x] = dst; } } }