Add performance improvements to TODO

TODO.md

@@ -1,10 +1,19 @@
 # TODO
 - Resolve relative paths, or paths with a `~` correctly.
-- Don't draw pixels outside screen.
 - Add alpha support.
-- Do not draw invisible (alpha) pixels.
 - Instantly update images in painter threads,
   not just when the stopped drawing.
-- Process all images at start.
-- Combine many pixel messages to improve performance.
 - Create a small listening server, to benchmark throughput.
+
+# Further optimizations
+- Process and slice all images before starting, don't process them each frame
+  again.
+- Create a pixel map at start, instead of continuously getting pixels from the
+  image.
+- Convert whole image blocks to a single large command string, to push in one
+  piece to the pixelflut server. Instead of pushing each pixel command
+  separately.
+- Do not draw transparant (alpha) pixels.
+- Do not draw pixels outside the screen size.
+- Further control buffering in drawing pipes.
+- Allow UDP mode (for pixelflut servers that support it).