1 files changed, 46 insertions, 0 deletions
diff --git a/camera.lua b/camera.lua
new file mode 100644
index 0000000..19c5bd4
--- /dev/null
+++ b/camera.lua
@@ -0,0 +1,46 @@
+local class = require'r.class'
+local Pos = require'r.pos'
+
+-- in screen units
+
+-- zoom is screen pixels per world unit
+local Camera = class()
+function Camera.make(cls,pos,zoom)
+	pos = pos or Pos:make(0,0)
+	zoom = zoom or 1
+	return setmetatable({pos=pos,zoom=zoom},cls)
+end
+local function screen_offset()
+	-- in screen units, not in world units !
+	local W,H = love.graphics.getDimensions()
+	return Pos:make(W/2,H/2)
+end
+function Camera.apply_trans(self)
+	local so = screen_offset()
+
+	-- centre (0,0) in the middle of the screen
+	love.graphics.translate(so.x,so.y)
+
+	-- apply camera transformations
+	love.graphics.scale(self.zoom)
+	love.graphics.translate(-self.pos.x,-self.pos.y)
+end
+
+function Camera.screen_to_world(self,pos)
+	local so = screen_offset()
+	return (pos-so)/self.zoom + self.pos
+end
+function Camera.world_to_screen(self,pos)
+	local so = screen_offset()
+	return (pos-self.pos) * self.zoom + so
+end
+
+function Camera.extents(self)
+	local W,H = love.graphics.getDimensions()
+	-- returns top left and bottom right pos's in world coords
+	return self:screen_to_world(Pos:make(0,0)),
+			self:screen_to_world(Pos:make(W,H))
+end
+
+
+return Camera