Implement pixels as RGBX structure.

- Add ‘make debug’ target
- Add links in README

TODO.md

@@ -1,25 +1,31 @@
-[-] Quaternions
-[X] Draw rotated pixels in src order
+[-] Draw rotated pixels in src order -> cache write miss
 [X] Use atan2 at beginning and end of line.
     Interpolation in-between values
 [X] Test pixel perfect 90
 [ ] Fix out-of-bounds pixel set
 
 [ ] Optimization for square images?
-[X] Fixed point computation?
-[-] -funroll-loops
+[X] Fixed point computation
+[-] -funroll-loops -> no gain
+[-] restrict qualifier -> unavailable in C++
 
 # Cache
 [-] Rotate per channel -> no gain
-[ ] Load pixels in 64-bit variable
 [X] Cut image in tiles
  [X] Overlap
  [-] Rotate in one temp tile then copy/move it
  [X] Align tiles in memory
-[-] Align memory -> no gain
-[ ] RGBX format
+
+## Alignement
+[X] RGBX format (create pixel structure) on 8 bytes (can do computation in-place)
+[ ] Load pixels in 64-bit variable
+[ ] Align memory on 16 bytes
+
+## Layout
+[ ] Pack 4 neighbors in 16B structure (aligned)
+    Each point is followed by the point below
 [ ] Spiral layout?
 
 # Quality
-[X] Interpolate using SIMD, SSE (no big gain)
+[X] Interpolate using SIMD, SSE (no big gain, alignement problem?)
 [ ] Image borders