Implement unit circle example

`unit_circle.sh` generates a animated GIF of the circle states between
p=1 and p=3.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/color.h b/src/color.h
index 514c739..dcad5cf 100644
--- a/src/color.h
+++ b/src/color.h
@@ -7,6 +7,8 @@ namespace imgen {
 
 using color = std::tuple<std::uint8_t, std::uint8_t, std::uint8_t>;
 
+constexpr color black()   { return color{  0,   0,   0}; }
+constexpr color white()   { return color{255, 255, 255}; }
 constexpr color red()     { return color{255,   0,   0}; }
 constexpr color lime()    { return color{  0, 255,   0}; }
 constexpr color blue()    { return color{  0,   0, 255}; }