Function gui_gdoverlay

src/lua-engine.cpp:4681–4814

gui.gdoverlay([int dx=0, int dy=0,] string str [, sx=0, sy=0, sw, sh] [, float alphamul=1.0]) Overlays the given image on the screen. example: gui.gdoverlay(gd.createFromPng("myimage.png"):gdStr())

//  Overlays the given image on the screen.
// example: gui.gdoverlay(gd.createFromPng("myimage.png"):gdStr())
static int gui_gdoverlay(lua_State *L) {

	int argCount = lua_gettop(L);

	int xStartDst = 0;
	int yStartDst = 0;
	int xStartSrc = 0;
	int yStartSrc = 0;

	int index = 1;
	if(lua_type(L,index) == LUA_TNUMBER)
	{
		xStartDst = lua_tointeger(L,index++);
		if(lua_type(L,index) == LUA_TNUMBER)
			yStartDst = lua_tointeger(L,index++);
	}

	luaL_checktype(L,index,LUA_TSTRING);
	const unsigned char* ptr = (const unsigned char*)lua_tostring(L,index++);

	if (ptr[0] != 255 || (ptr[1] != 254 && ptr[1] != 255))
		luaL_error(L, "bad image data");
	bool trueColor = (ptr[1] == 254);
	ptr += 2;
	int imgwidth = *ptr++ << 8;
	imgwidth |= *ptr++;
	int width = imgwidth;
	int imgheight = *ptr++ << 8;
	imgheight |= *ptr++;
	int height = imgheight;
	if ((!trueColor && *ptr) || (trueColor && !*ptr))
		luaL_error(L, "bad image data");
	ptr++;
	int pitch = imgwidth * (trueColor?4:1);

	if ((argCount - index + 1) >= 4) {
		xStartSrc = luaL_checkinteger(L,index++);
		yStartSrc = luaL_checkinteger(L,index++);
		width = luaL_checkinteger(L,index++);
		height = luaL_checkinteger(L,index++);
	}

	int alphaMul = transparencyModifier;
	if(lua_isnumber(L, index))
		alphaMul = (int)(alphaMul * lua_tonumber(L, index++));
	if(alphaMul <= 0)
		return 0;

	// since there aren't that many possible opacity levels,
	// do the opacity modification calculations beforehand instead of per pixel
	int opacMap[256];
	for(int i = 0; i < 128; i++)
	{
		int opac = 255 - ((i << 1) | (i & 1)); // gdAlphaMax = 127, not 255
		opac = (opac * alphaMul) / 255;
		if(opac < 0) opac = 0;
		if(opac > 255) opac = 255;
		opacMap[i] = opac;