From 5872a931e1818b98f717f0c2c0226f511d5adbf7 Mon Sep 17 00:00:00 2001
From: hkc <hatkidchan@gmail.com>
Date: Thu, 18 Jan 2024 16:26:57 +0300
Subject: [PATCH] CPIv1 implementation added

---
 cc-pic.py | 29 ++++++++++++++++---
 ccpi.lua  | 84 ++++++++++++++++++++++++++++++++++++++++++-------------
 2 files changed, 90 insertions(+), 23 deletions(-)

diff --git a/cc-pic.py b/cc-pic.py
index 85d175f..fc622bc 100644
--- a/cc-pic.py
+++ b/cc-pic.py
@@ -78,14 +78,35 @@ class Converter:
             dark_i, bri_i = bri_i, dark_i
         return out, dark_i, bri_i
 
+    @staticmethod
+    def _write_varint(fp: BinaryIO, value: int):
+        value &= 0xFFFFFFFF
+        mask: int = 0xFFFFFF80
+        while True:
+            if (value & mask) == 0:
+                fp.write(bytes([value & 0xFF]))
+                return
+            fp.write(bytes([(value & 0x7F) | 0x80]))
+            value >>= 7
+
     def export_binary(self, io: BinaryIO):
-        io.write(b"CCPI")
-        io.write(bytes([self._img.width // 2, self._img.height // 3, 0]))
-        io.write(bytes(self._palette[: 16 * 3]))
+        if self._img.width <= 510 and self._img.height <= 765:
+            io.write(b"CCPI") # old format
+            io.write(bytes([self._img.width // 2, self._img.height // 3, 0]))
+            io.write(bytes(self._palette[: 16 * 3]))
+        else:
+            io.write(b"CPI\x01") # CPIv1
+            self._write_varint(io, self._img.width // 2)
+            self._write_varint(io, self._img.height // 3)
+            io.write(bytes(self._palette[: 16 * 3]))
+        written = 0
         for y in range(0, self._img.height - 2, 3):
+            line: bytearray = bytearray()
             for x in range(0, self._img.width - 1, 2):
                 ch, bg, fg = self._get_block(x, y)
-                io.write(bytes([(ch + 0x80) & 0xFF, fg << 4 | bg]))
+                line.extend([(ch + 0x80) & 0xFF, fg << 4 | bg])
+            written += io.write(line)
+        assert written == (self._img.width // 2) * (self._img.height // 3) * 2
 
     def export(self, io: TextIO):
         io.write("local m = peripheral.find('monitor')\n")
diff --git a/ccpi.lua b/ccpi.lua
index b230169..f82c820 100644
--- a/ccpi.lua
+++ b/ccpi.lua
@@ -1,30 +1,20 @@
 
-local function load(path)
-    local image = { w = 0, h = 0, scale = 1.0, palette = {}, lines = {} }
+local decoders = {}
 
-    local fp, err = io.open(path, "rb")
-    if not fp then return nil, err end
-
-    local magic = fp:read(4)
-    if magic ~= "CCPI" then
-        return nil, "Invalid header: expected CCPI got " .. magic
-    end
-
-    image.w, image.h = string.byte(fp:read(1)), string.byte(fp:read(1))
-    image.scale = 0.5 + string.byte(fp:read(1)) * 5 / 255
+local function read_palette_full(palette, fp)
     for i = 1, 16 do
-        image.palette[i] = bit.blshift(string.byte(fp:read(1)), 16)
-        image.palette[i] = bit.bor(image.palette[i], bit.blshift(string.byte(fp:read(1)), 8))
-        image.palette[i] = bit.bor(image.palette[i], string.byte(fp:read(1)))
+        palette[i] = bit.blshift(string.byte(fp:read(1)), 16)
+        palette[i] = bit.bor(palette[i], bit.blshift(string.byte(fp:read(1)), 8))
+        palette[i] = bit.bor(palette[i], string.byte(fp:read(1)))
     end
+end
 
-    print(image.w, image.h)
-
+local function read_pixeldata_v0(image, fp)
     for y = 1, image.h do
         local line = { s = "", bg = "", fg = "" }
         for x = 1, image.w do
             local data = fp:read(2)
-            if #data == 0 then
+            if data == nil or #data == 0 then
                 return nil, string.format("Failed to read character at x=%d y=%d", x, y)
             end
 
@@ -39,9 +29,65 @@ local function load(path)
         end
         table.insert(image.lines, line)
     end
+    return true
+end
+
+local function read_varint(fp)
+    local value = 0
+    local current = 0
+    local offset = 0
+    repeat
+        if offset >= 5 then return nil, "varint too long" end
+        current = string.byte(fp:read(1))
+        value = bit.bor(value, bit.blshift(bit.band(current, 0x7f), offset * 7))
+        offset = offset + 1
+    until bit.band(current, 0x80) == 0
+    return value
+end
+
+decoders[0] = function(image, fp)
+    image.w, image.h = string.byte(fp:read(1)), string.byte(fp:read(1))
+    image.scale = 0.5 + string.byte(fp:read(1)) * 5 / 255
+    read_palette_full(image.palette, fp)
+    local success, err = read_pixeldata_v0(image, fp)
+    if not success then return false, err end
+    return true
+end
+
+decoders[1] = function(image, fp)
+    image.w = read_varint(fp)
+    image.h = read_varint(fp)
+    image.scale = 0.5 -- CPIv1 doesn't have a scale property
+    read_palette_full(image.palette, fp)
+    local success, err = read_pixeldata_v0(image, fp)
+    if not success then return false, err end
+    return true
+end
+
+local function load(path)
+    local fp, err = io.open(path, "rb")
+    if not fp then return nil, err end
+
+    local res
+    local image = { w = 0, h = 0, scale = 1.0, palette = {}, lines = {} }
+
+    local magic = fp:read(4)
+    if magic == "CCPI" then
+        res, err = decoders[0](image, fp)
+    elseif magic:sub(1, 3) == "CPI" then
+        local version = magic:byte(4, 4)
+        if decoders[version] == nil then
+            fp:close()
+            return nil, string.format("Invalid CPI version 0x%02x", version)
+        end
+        res, err = decoders[version](image, fp)
+    else
+        fp:close()
+        return nil, "Invalid header: expected CCPI got " .. magic
+    end
 
     fp:close()
-
+    if not res then return false, err end
     return image
 end