Add GCD grid example

README.org

@@ -22,6 +22,8 @@ cd examples
 make all
 #+end_src
 
+[[./examples/gcdgrid.png]]
+
 [[./examples/hsv.png]]
 [[./examples/gradient.png]]
 

examples/Makefile

@@ -1,5 +1,5 @@
 .PHONY: all
-all: checkers.png random_pbm.png random_pgm.png random_ppm.png gradient.png hsv.png
+all: checkers.png random_pbm.png random_pgm.png random_ppm.png gradient.png hsv.png gcdgrid.png
 
 %.pnm: %.bqn
 	bqn $< > $@

examples/gcdgrid.bqn

@@ -0,0 +1,12 @@
+bqngraphics←"../"
+⟨Viridis⟩←•Import bqngraphics∾"colormaps.bqn"
+⟨HSVtoRGB⟩←•Import bqngraphics∾"colors.bqn"
+⟨PBM,PGM,PPM⟩←•Import bqngraphics∾"pnm.bqn"
+
+# https://susam.net/blog/gcd-grid.html
+GCDGrid←•math.GCD⌜˜↕
+
+•Out PBM 1≠GCDGrid 50
+#•Out PGM GCDGrid 20
+#•Out PPM {⌊255×HSVtoRGB⎉1⍉(360×𝕩÷1+⌈˝𝕩)∾(2∾≢𝕩)⥊1}GCDGrid 20
+#•Out PPM ⌊255×> Viridis¨ (⊢÷⌈´∘⥊) GCDGrid 20