--[[
OC Efficient image file format
this is a space efficient and fast rendering algorithm for non text images
it tries to reduce images to a small number of fills instead of setting each pixel individually
header:
string "OCI"
version: byte
meta: zero terminated string
width: byte

repeat:
color: byte
width: byte
height: byte
]]--

local component=require("component")
local s=require("serialization")

local oci={}
local version=0

--[[
encodes an image to another format
modes:
oci:
default output
xy24:
default input
data[x][y]=24 bit color
yx24:
data[y][x]=24 bit color
xy8:
data[x][y]=8 bit color
yx8:
data[y][x]=8 bit color
<number> or str:
image is encoded as a string with 8 bit colors and width is <number>
returns output,width,height
]]

local function round(num)
return math.floor(num+0.5)
end

local function c24to8(num)
return round(bit32.rshift(num,16)*7/255)*32+round((bit32.rshift(num,8)%256)*7/255)*4+round((num%256)*3/255)
end

local function c8to24(c)
return round(math.floor(c/32)*255/7)*65536+round((math.floor(c/4)%8)*255/7)*256+round((c%4)*255/3)
end

local function encode(data,mode,omode,meta)
mode=mode or "xy24"
omode=omode or "oci"
local inp={}
local wd
local hi
if mode=="oci" then
if data:sub(1,3)~="OCI" then
error("invalid OCI data")
end
data=data:sub(4)
local version=data:byte(1,1)
local meta,width,data=data:match("^.(.-)%z(.)(.+)")
width=width:byte()
wd=width
hi=0
local x=1
local y=1
for l1=1,#data,3 do
local c=c8to24(data:byte(l1))
local w=data:byte(l1+1)
local h=data:byte(l1+2)
hi=math.max(hi,(h+y)-1)
-- fill space
for cy=y,(h+y)-1 do
inp[cy]=inp[cy] or {}
for cx=x,(w+x)-1 do
inp[cy][cx]=c
end
end
-- find next pixel
if x+w>width then
x=1
y=h+y
else
x=x+w
end
end
elseif mode=="xy24" then
wd=#data
hi=#(data[1] or {})
for x=1,#data do
local c=data[x]
hi=#c
for y=1,#c do
inp[y]=inp[y] or {}
inp[y][x]=data[x][y]
end
end
elseif mode=="yx24" then
wd=#(data[1] or {})
hi=#data
inp=data
elseif mode=="xy8" then
wd=#data
hi=#(data[1] or {})
for x=1,#data do
local c=data[x]
for y=1,#c do
inp[y]=inp[y] or {}
inp[y][x]=c8to24(c[y])
end
end
elseif mode=="yx8" then
wd=#(data[1] or {})
hi=#data
for y=1,#data do
inp[y]={}
local c=data[y]
for x=1,#c do
inp[y][x]=c8to24(c[x])
end
end
elseif tonumber(mode) then
local w=tonumber(mode)
if #data%w~=0 then
error("invalid data")
end
for l1=1,#data do
local x=((l1-1)%w)+1
local y=math.floor(l1/w)+1
inp[y]=inp[y] or {}
inp[y][x]=c8to24(data:byte(l1,l1))
end
else
error("no such mode: "..tostring(mode))
end
local out
if omode=="oci" then
-- this can be slow on large images
local ot={}
local ud=setmetatable({},{__index=function(s,n)
local o={}
s[n]=o
return o
end})
-- generate
for y=1,hi do
ot[y]={}
local c=inp[y]
for x=1,wd do
local cc=c[x]
if not ud[y][x] then
local mx=y+x
local ct={y,x}
local pmn=wd
for cy=y,hi do
if inp[cy][x]~=cc then
break
end
local m=x
for cx=x,pmn do
if inp[cy][cx]~=cc then
break
end
m=cx
end
pmn=math.min(pmn,m)
if m+cy>mx then
ct={cy,m}
end
end
for sy=y,ct[1] do
for sx=x,ct[2] do
ud[sy][sx]=true
end
end
ot[y][x]=ct
end
end
end
out="OCI"..string.char(version).."\0"..string.char(wd)
for y=1,hi do
local c=ot[y]
for x=1,wd do
local cc=c[x]
if cc then
out=out..string.char(c24to8(inp[y][x]))..string.char((cc[2]-x)+1)..string.char((cc[1]-y)+1)
end
end
end
elseif omode=="xy24" then
out={}
for x=1,wd do
out[x]={}
for y=1,hi do
out[x][y]=inp[y][x]
end
end
elseif omode=="yx24" then
out=inp
elseif omode=="xy8" then
out={}
for x=1,wd do
out[x]={}
for y=1,hi do
out[x][y]=c24to8(inp[y][x])
end
end
elseif omode=="yx8" then
out={}
for y=1,hi do
out[y]={}
for x=1,wd do
out[y][x]=c24to8(inp[y][x])
end
end
elseif omode=="str" then
out=""
for y=1,hi do
for x=1,wd do
out=out..string.char(c24to8(inp[y][x]))
end
end
end
return out,wd,hi
end

--[[
renders an oci image
x and y are start of image, defaults to 1
]]

local function render(data,x,y)
if data:sub(1,3)~="OCI" then
error("invalid OCI")
end
data=data:sub(4)
local gpu=component.gpu
x=x or 1
y=y or 1
local version=data:byte(1,1)
local odata=data
local meta,width,data=data:match("^.(.-)%z(.)(.+)$")
width=width:byte()
local cx=1
local cy=1
if #data%3~=0 then
error("invalid OCI "..#data..","..(#data%3))
end
local f=setmetatable({},{__index=function(s,n)
local o={}
s[n]=o
return o
end})
for l1=1,#data,3 do
local w=data:byte(l1+1)
local h=data:byte(l1+2)
-- fill space
gpu.setBackground(c8to24(data:byte(l1)))
gpu.fill(x+cx-1,y+cy-1,w,h," ")
for sy=cy,cy+h-1 do
for sx=cx,cx+w-1 do
f[sy][sx]=true
end
end
-- find next pixel
while f[cy][cx] do
cx=cx+1
cy=cy+math.floor(cx/(width+1))
cx=((cx-1)%width)+1
end
end
end

return {
encode=encode,
render=render,
}