Get pixel alpha of a quad

[pauls313]

In my tile-based game, if the player clicks an item I want to know if the coords where he clicked are part of the item sprite or not, thus I check the alpha.

While iterating through the items, it uses this function to render each: love.graphics.draw(obj.image,obj.quad,x * drawsize,y * drawsize,0,drawsize / 32,drawsize / 32)

And there also is camera translation.
I'm not really good at this kind of thing so I've been cracking my head for two days now trying to realize how should I convert world touch coordinates into local image and quad coordinates. I made this function but the conversion isn't working:

Code: Select all

function overimage(image,quad,xx,yy)
   local imgdata = image:getData()
   local quadx,quady = quad:getViewport()
   
   local localx = touch.x + camera.dx - xx
   local localy = touch.y + camera.dy - yy
   
   local r,g,b,a = imgdata:getPixel(localx,localy)
   
   if touch.beingpressed then
      if a > 50 then
         return true
      end
   end
end

If someone could show to me how to do that, it would be a great help!