From 28f9cb9b984621a6f1868e0d70454ee72e7f2031 Mon Sep 17 00:00:00 2001
From: ubq323 <ubq323@ubq323.website>
Date: Sat, 30 Mar 2024 22:41:12 +0000
Subject: launch framebuf

---
 framebuf.lua | 210 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 210 insertions(+)
 create mode 100644 framebuf.lua

diff --git a/framebuf.lua b/framebuf.lua
new file mode 100644
index 0000000..bf0dac4
--- /dev/null
+++ b/framebuf.lua
@@ -0,0 +1,210 @@
+local M = {}
+
+local hex_digits = {
+	"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"
+}
+
+function M.new()
+	return setmetatable({}, M)
+end
+
+function M:__newindex(k, v)
+	error("assignment to framebuffer object", 2)
+end
+
+function M:__index(k)
+	if type(k) == "number" and math.floor(k) == k then
+		rawset(self, k, {})
+		return rawget(self, k)
+	else
+		return M[k]
+	end
+end
+
+function M:clear()
+	for k in pairs(self) do
+		if type(k) == "number" then
+			self[k] = nil
+		end
+	end
+end
+
+local function round(x, y)
+	return math.floor(x + 0.5), math.floor(y + 0.5)
+end
+
+function M:plot(x, y, r, g, b)
+	local x, y = round(x, y)
+	self[x][y] = colors.packRGB(r, g, b)
+end
+
+function M:get(x, y)
+	local x, y = round(x, y)
+	if self[x][y] then
+		return colors.unpackRGB(self[x][y])
+	end
+end
+
+function M:rect(x1, y1, x2, y2, r, g, b)
+	for x = x1, x2 do
+		for y = y1, y2 do
+			self:plot(x, y, r, g, b)
+		end
+	end
+end
+
+function M:ppm(data, x, y)
+	if type(data) ~= "string" then
+		local f = data
+		data = assert(f.readAll())
+		f.close()
+	end
+	local x, y = round(x or 1, y or 1)
+	local w, h, depth, data = data:match "^P6\n(%d+) (%d+)\n(%d+)\n(.+)"
+	assert(w and h and depth, "invalid format; binary PPM (P6) requried")
+	for dy = 1, h do
+		for dx = 1, w do
+			local i = (((dy - 1) * w + dx) - 1) * 3
+			local r, g, b =
+				data:byte(i + 1) / depth,
+				data:byte(i + 2) / depth,
+				data:byte(i + 3) / depth
+			self:plot(dx + x - 1, dy + y - 1, r, g, b)
+		end
+	end
+end
+
+-- determine a palette for a set of colors
+local function median_cut(cols, nbuckets)
+	local max, min = {}, {}
+	for _, color in ipairs(cols) do
+		for ch, v in ipairs(color) do
+			if not max[ch] or v > max[ch] then max[ch] = v end
+			if not min[ch] or v < min[ch] then min[ch] = v end
+		end
+	end
+	local max_variance, max_variant
+	for ch in ipairs(max) do
+		local variance = max[ch] - min[ch]
+		if not max_variance or variance > max_variance then
+			max_variance = variance
+			max_variant = ch
+		end
+	end
+	table.sort(cols, function(a, b) return a[max_variant] <= b[max_variant] end)
+	local partitions = {{}, {}}
+	local half = math.floor(#cols / 2)
+	for i = 1, half do
+		table.insert(partitions[1], cols[i])
+	end
+	for i = half + 1, #cols do
+		table.insert(partitions[2], cols[i])
+	end
+	local palette, map = {}, {}
+	if nbuckets <= 2 then
+		for n, part in ipairs(partitions) do
+			local avg = {0, 0, 0}
+			for _, color in ipairs(part) do
+				for ch, v in ipairs(color) do
+					avg[ch] = avg[ch] + v
+				end
+				map[colors.packRGB(unpack(color))] = n
+			end
+			for ch, v in ipairs(avg) do
+				avg[ch] = avg[ch] / #part
+			end
+			palette[n] = colors.packRGB(unpack(avg))
+		end
+	else
+		local palette1, map1 = median_cut(partitions[1], nbuckets / 2)
+		local palette2, map2 = median_cut(partitions[2], nbuckets / 2)
+		for b, m in pairs {[palette1] = map1, [palette2] = map2} do
+			local offs = #palette
+			for i, b in ipairs(b) do
+				palette[i + offs] = b
+			end
+			for c, i in pairs(m) do
+				map[c] = i + offs
+			end
+		end
+	end
+	return palette, map
+end
+
+local function get_char(fb, x, y)
+	local cols = {}
+	local pixels = {}
+	for y = y, y + 2 do
+		for x = x, x + 1 do
+			local color = {fb:get(x, y)}
+			if color[1] then
+				table.insert(cols, color)
+				table.insert(pixels, colors.packRGB(unpack(color)))
+			else
+				table.insert(pixels, 0)
+			end
+		end
+	end
+	if #cols == 0 then
+		return string.char(0x80)
+	end
+	local palette, map = median_cut(cols, 2)
+	local char = 0x80
+	-- TODO: document this
+	local p6 = map[pixels[6]] or 1
+	for i = 1, 5 do
+		if (map[pixels[i]] or 1) ~= p6 then
+			char = char + 2^(i - 1)
+		end
+	end
+	local fg, bg
+	if map[pixels[6]] == 2 then
+		fg, bg = palette[1], palette[2]
+	else
+		fg, bg = palette[2], palette[1]
+	end
+	return string.char(char), fg, bg
+end
+
+function M.resolution()
+	local w, h = term.getSize()
+	return w * 2, h * 3
+end
+
+function M:present(offsx, offsy)
+	offsx, offsy = offsx or 0, offsy or 0
+	local w, h = term.getSize()
+	local pw, ph = M.resolution()
+	local cols = {}
+	local chars = {}
+	for y = offsy + 1, offsy + ph, 3 do
+		for x = offsx + 1, offsx + pw, 2 do
+			local char, fg, bg = get_char(self, x, y)
+			table.insert(chars, {char, fg, bg})
+			if fg and bg then
+				table.insert(cols, {colors.unpackRGB(fg)})
+				table.insert(cols, {colors.unpackRGB(bg)})
+			end
+		end
+	end
+	local palette, map = median_cut(cols, 16)
+	for i, color in ipairs(palette) do
+		term.setPaletteColor(2^(i - 1), color) 
+	end
+	for i = 1, w * h, w do
+		term.setCursorPos(1, (i - 1) / w)
+		local blit_char, blit_fg, blit_bg = {}, {}, {}
+		for i = i, i + w - 1 do
+			local char, fg, bg = unpack(chars[i])
+			table.insert(blit_char, char)
+			table.insert(blit_fg, fg and hex_digits[map[fg]] or "1")
+			table.insert(blit_bg, bg and hex_digits[map[bg]] or "1")
+		end
+		term.blit(
+			table.concat(blit_char),
+			table.concat(blit_fg),
+			table.concat(blit_bg))
+	end
+end
+
+return M
-- 
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