change raster method, add todo to readme

README.md

@@ -5,7 +5,7 @@ make sure you have nix installed
 curl https://nixos.org/nix/install | sh
 ```
 
-to build:
+### to build:
 ```
 nix-build
 
@@ -15,7 +15,7 @@ run with
 ./result/bin/image-triangles -o output.svg
 ```
 
-to develop on:
+### to develop on:
 ```
 cabal --enable-nix build
 ```
@@ -29,3 +29,15 @@ run with
 ```
 ./dist/build/image-triangles/image-triangles -o output.svg
 ```
+
+### todo
+    - Why is the area wrong for the top right corner?
+    - Rasterization for triangles
+    - Cmdline interface that lets you set number of triangles, and smallness
+    - Pointy triangle filter
+    - Confirm diagrams is rendering triangles in the correct places.
+    - Cache transformations to the colors library
+    - Hip has a map transformation. It also depends on the colours library, does it use it?
+    - Check that hip colors are srgb
+    - Think about opacity. What if everything was completely opaque? What should we do with areas that aren’t 100% covered at the end?
+