pico-8 cartridge // http://www.pico-8.com
version 41
__lua__
-- sprite-sampled palette
-- kistaro@gmail.com

function _init()
 -- lock top 16 rows to default palette
 pal({[0]=0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15}, 2)
 poke(0x5f5f, 0x10)
 poke2(0x5f70, 0xffff)
end

function _update()
end

function _draw()
 cls()
 draw_hud()
 draw_bars()
end

function draw_hud()
end

function draw_bars()
 for i=0,15 do
  local i7 = i * 7
  rectfill(0,16+i7,128,i7+22,i)
 end
end
-->8
-- palette structure

palette = {
 -- cols: table. identical
 --       format to table-type
 --       pal call
 
 --   tr: transparency table.
 --       keys: [0]..[15]
 --         (color indexes)
 --       vals: true/false/nil
 --         for transparency of
 --         that color. false
 --         sets opaque, nil
 --         means "do not set".
 --       tables with no absent
 --       values can be compiled
 --       for faster do_palt.

 -- cpl_tr: compiled tr. set by
 --       compile_palt iff all
 --       tr values in range
 --       are nonnil. do_palt
 --       is faster this way
}
palette_mt = {__index=palette}

function palette.new(x)
 x = x or {}
 if (not x.cols) x.cols = {}
 if (not x.tr) x.tr = {}
 setmetatable(x, palette_mt)
end

function palette:do_pal(p)
 pal(self.cols, p)
end

function palette:do_palt()
 if (self.cpl_tr) return palt(self.cpl_tr)
 local tr = self.tr
 for i=0,15 do
  if (tr[i] ~= nil) palt(i, tr[i])
 end
end

function palette:do_both(p)
 self:do_palt()
 self:do_pal(p)
end

function palette:compile_palt()
 self.cpl_tr = nil
 local bits, tr = 0, self.tr
 for i = 15,0,-1 do
  if (tr[i] == nil) return
  bits <<= 1
  if (tr[i]) bits += 1
 end
 self.cpl_tr = bits
 return bits
end
__gfx__
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
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00700700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00077000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00077000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00700700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000