From 80f58af6970bc8ed7079de2d6c1f6d66bb139332 Mon Sep 17 00:00:00 2001
From: ubq323 <ubq323@ubq323.website>
Date: Thu, 4 Aug 2022 22:23:48 +0100
Subject: load_pnm

---
 img/load_pnm.lua | 127 ++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 107 insertions(+), 20 deletions(-)

(limited to 'img/load_pnm.lua')

diff --git a/img/load_pnm.lua b/img/load_pnm.lua
index 60cac8a..1cd228c 100644
--- a/img/load_pnm.lua
+++ b/img/load_pnm.lua
@@ -1,34 +1,121 @@
-local perr = require("util").perr
+-- only going to support binary ones
+-- because the textual ones are annoying
 
-local function load_p1(fname)
+-- types:
+-- P1	ascii	pbm	
+-- P2	ascii	pgm
+-- P3	ascii	ppm
+-- P4	binary	pbm
+-- P5	binary	pgm
+-- P6	binary	ppm
 
-	local file,err = fs.open(fname,"r")
-	perr(err,"fs.open")
-	local imgf = file.readAll()
-	--print(img)
-	assert(imgf:sub(1,2) == "P1","only P1 images are supported at the moment")
-	local width,height, cur = imgf:match("%s*(%d+)%s*(%d+)%s*()",3)
-	assert(width,"couldn't find image header")
 
-	local img=setmetatable({},{__index=function(t,k)
+-- function nextpixel(imgf,cur,depth) -> pixel, ncur
+-- where pixel is {r,g,b}, with r,g,b in [0,1]
+
+local function np_p1(imgf,cur,depth)
+	local val,ncur = imgf:match("[01]%s*()",cur)
+	val = tonumber(val)
+	assert(val,"bad image format at "..cur)
+	local p = (1-v) -- 1 is black (0), 0 is white (1)
+	local pixel = {p,p,p}
+	return pixel,ncur
+end
+local function np_p2(imgf,cur,depth)
+	local val,ncur = imgf:match("(%d+)%s+()",cur)
+	val = tonumber(val)
+	assert(val,"bad image format at "..cur)
+	assert(0<=val and val<=depth, "image value out of range at "..cur)
+	local p = val/depth
+	local pixel = {p,p,p}
+	return pixel,ncur
+end
+local function np_p3(imgf,cur,depth)
+	local tr,tg,tb,ncur = imgf:match("(%d+)%s+(%d+)%s+(%d+)%s+()",cur)
+	local vr,vg,vb = tonumber(tr),tonumber(tg),tonumber(tb)
+	assert(vr,"bad image format at "..cur)
+	for _,v in ipairs{vr,vg,vb} do
+		assert(0<=v and v<=depth,"image value out of range at "..cur)
+	end
+	local pr,pg,pb = vr/depth,vg/depth,vb/depth
+	local pixel = {pr,pg,pb}
+	return pixel,ncur
+end
+-- i will figure this one out later
+local function np_p4() error("p4 isn't supported yet") end
+local function np_p5(imgf,cur,depth)
+	local val = imgf:byte(cur)
+	assert(val<=depth,"image value out of range at "..cur)
+	local p = val/depth
+	local pixel = {p,p,p}
+	return pixel,cur+1
+end
+local function np_p6(imgf,cur,depth)
+	local vr,vg,vb = img:byte(cur,cur+3)
+	for _,v in ipairs{vr,vg,vb} do
+		assert(0<=v and v<=depth, "image value out of range at "..cur)
+	end
+	local pr,pg,pb = vr/depth,vg/depth,vb/depth
+	local pixel = {pr,pg,pb}
+	return pixel,cur+3
+end
+
+local nextpixel_fns = {
+	[1]=np_p1,
+	[2]=np_p2,
+	[3]=np_p3,
+	[4]=np_p4,
+	[5]=np_p5,
+	[6]=np_p6,
+}
+
+
+local function parse(imgf)
+	assert(imgf:sub(1,1) == "P","invalid header")
+	local typech = tonumber(imgf:sub(2,2))
+	assert(typech and 1<=typech and typech<=6,"invalid header type")
+
+	local has_depth = not(typech == 1 or typech == 4)
+
+	local width,height,cur = imgf:match("%s*(%d+)%s*(%d+)%s*()",3)
+	assert(width,"couldn't find image dimensions")
+
+	-- by 'depth' i mean 'maximum value'
+	local depth = 1
+	if has_depth then
+		local ndepth,ncur = imgf:match("(%d+)%s*()")
+		assert(ndepth,"couldn't find image depth (max pixel value), in a format that needs it")
+		depth=ndepth
+		cur=ncur
+	end
+	assert(depth<=255,"depth too high (shouldn't be above 255)")
+
+	-- img[y][x]; 1,1 is top left
+	local img = setmetatable({},{__index=function(t,k)
 		if type(k) ~= "number" then return nil end
 		local r = {}
 		rawset(t,k,r)
 		return r
 	end})
 
-	-- img[y][x]. 1,1 is top left
-	for row=1,height do
-		for col =1,width do
-			local val,ncur = imgf:match("(%d+)%s*()",cur)
-			cur = ncur
-			img[row][col] = tonumber(val)
+	local x,y=1,1
+	local nextpixel = nextpixel_fns[typech]
+	
+	while cur <= #imgf do
+		local npixel,ncur = nextpixel(imgf,cur,depth)
+		img[y][x] = npixel
+		cur = ncur
+		if y > width then
+			y = 1
+			x = x + 1
+		end
+		if x > height then
+			break
 		end
 	end
-
-	img.width=width
-	img.height=height
+	
+	img.width = width
+	img.height = height
 	return img
 end
 
-return load_p1
-- 
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