Function CreateMask

src/bitmap.cpp:587–611

namespace {
	PixmanImagePtr CreateMask(Opacity const& opacity, Rect const& src_rect, Transform const* pxform = nullptr) {
		if (opacity.IsOpaque()) {
			return nullptr;
		}

		if (!opacity.IsSplit()) {
			pixman_color_t tcolor = {0, 0, 0, static_cast<uint16_t>(opacity.Value() << 8)};
			return PixmanImagePtr{ pixman_image_create_solid_fill(&tcolor) };
		}

		auto mask = PixmanImagePtr{pixman_image_create_bits(PIXMAN_a8, 1, 2, (uint32_t*) NULL, 4)};
		uint32_t* pixels = pixman_image_get_data(mask.get());
		*reinterpret_cast<uint8_t*>(&pixels[0]) = (opacity.top & 0xFF);
		*reinterpret_cast<uint8_t*>(&pixels[1]) = (opacity.bottom & 0xFF);

		Transform xform = Transform::Scale(1.0 / src_rect.width, 1.0 / src_rect.height);
		xform *= Transform::Translation(0, opacity.split);

		if (pxform)
			xform *= *pxform;

		pixman_image_set_transform(mask.get(), &xform.matrix);

		return mask;
	}
} // anonymous namespace

void Bitmap::Blit(int x, int y, Bitmap const& src, Rect const& src_rect, Opacity const& opacity, Bitmap::BlendMode blend_mode) {