postprocessor for 3dlut colcorr; dithering should be managed in "dirty" way

dirty way: loads dithered/passthru shader according to the game's config (boolean fxdither)

src/net/torvald/terrarum/PostProcessor.kt

@@ -0,0 +1,29 @@
+package net.torvald.terrarum
+
+import com.badlogic.gdx.Gdx
+import com.badlogic.gdx.graphics.GL20
+import com.badlogic.gdx.graphics.g2d.SpriteBatch
+import com.badlogic.gdx.graphics.glutils.FrameBuffer
+
+object PostProcessor {
+
+    private val batch = SpriteBatch()
+
+    fun draw(screenTexHolder: FrameBuffer) {
+        //Gdx.gl.glClearColor(.094f, .094f, .094f, 1f)
+        //Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT)
+
+
+        batch.shader = null
+        batch.inUse {
+            val texture = screenTexHolder.colorBufferTexture
+            batch.shader.setUniformMatrix("u_projTrans", batch.projectionMatrix)
+            batch.draw(texture, 0f, 0f, texture.width.toFloat(), texture.height.toFloat())
+        }
+
+
+        Gdx.gl.glActiveTexture(GL20.GL_TEXTURE0) // don't know why it is needed; it really depresses me
+
+    }
+
+}