Reading AND mask of 16x16 images from ICO file in Lua - image

Question

I am creating a function that will parse and ICO/CUR and convert the data into plain pixels (specific to my API) that will then be fed to a dxCreateTexture function which will create the final image. I'm currently working on the case when the images inside the ICO file are 8bpp or less. Here's how it's currently done:
I read the color palette and store each color inside an array.
I move on to reading the XOR mask which contains the indices for every pixel color and store every pixel inside another table.
I then read the AND mask which I understand is 1bpp.
The code that I will post below works perfectly for 1bpp, 4bpp and 8bpp images with a size of 32x32, XOR & AND masks being interpreted correctly, but for images with 8x8, 16x16 or 48x48 sizes (and I suspect that there are other sizes too) only the XOR mask gets interpreted correctly. Reading the AND mask will result in misplaced transparent pixels. Please keep in mind that I'm not flipping the image yet, so this code will result in an upside-down image.
local IcoSignature = string.char(0,0,1,0);
local PngSignature = string.char(137,80,78,71,13,10,26,10);
local AlphaByte = string.char(255);
local TransparentPixel = string.char(0,0,0,0);
function ParseCur(FilePath)
if (fileExists(FilePath) == true) then
local File = fileOpen(FilePath);
if (File ~= false) and (fileRead(File,4) == IcoSignature) then
local Icons = {}
for i = 1,fileReadInteger(File,2) do -- number of icons in file
local SizeX = fileReadInteger(File,1); -- icon width
if (SizeX == 0) then
SizeX = 256;
end
local SizeY = fileReadInteger(File,1); -- icon height
if (SizeY == 0) then
SizeY = 256;
end
fileRead(File,2); -- skip ColorCount and Reserved
local PlanesNumber = fileReadInteger(File,2);
local BitsPerPixel = fileReadInteger(File,2);
local Size = fileReadInteger(File); -- bytes occupied by icon
local Offset = fileReadInteger(File); -- icon data offset
Icons[i] = {
PlanesNumber = PlanesNumber,
BitsPerPixel = BitsPerPixel,
SizeX = SizeX,
SizeY = SizeY,
Texture = true
}
local PreviousPosition = fileGetPos(File);
fileSetPos(File,Offset);
if (fileRead(File,8) == PngSignature) then -- check data format (png or bmp)
fileSetPos(File,Offset);
-- to do
else
fileSetPos(File,Offset+4); -- skip BITMAPINFOHEADER Size
local SizeX = fileReadInteger(File);
local SizeY = fileReadInteger(File)/2;
local PlanesNumber = fileReadInteger(File,2);
local BitsPerPixel = fileReadInteger(File,2);
fileRead(File,24); -- skip rest of BITMAPINFOHEADER
local Pixels = {}
if (BitsPerPixel == 1) or (BitsPerPixel == 4) or (BitsPerPixel == 8) then
local Colors = {}
for j = 1,2^(PlanesNumber*BitsPerPixel) do
Colors[j] = fileRead(File,3)..AlphaByte;
fileRead(File,1);
end
local PixelsPerByte = 8/BitsPerPixel;
local CurrentByte;
for y = 1,SizeY do -- XOR mask
Pixels[y] = {}
local CurrentRow = Pixels[y];
for x = 0,SizeX-1 do
local CurrentBit = x%PixelsPerByte;
if (CurrentBit == 0) then
CurrentByte = fileReadInteger(File,1);
end
CurrentRow[x+1] = Colors[bitExtract(
CurrentByte,
(PixelsPerByte-1-CurrentBit)*BitsPerPixel,BitsPerPixel
)+1];
end
end
for y = 1,SizeY do -- AND mask
local CurrentRow = Pixels[y];
for x = 0,SizeX-1 do
local CurrentBit = x%8;
if (CurrentBit == 0) then
CurrentByte = fileReadInteger(File,1);
end
if (bitExtract(CurrentByte,7-CurrentBit,1) == 1) then
CurrentRow[x+1] = TransparentPixel;
end
end
end
for y = 1,SizeY do -- concatenate rows into strings
Pixels[y] = table.concat(Pixels[y]);
end
Icons[i].Texture = dxCreateTexture(
table.concat(Pixels)..string.char(
bitExtract(SizeX,0,8),bitExtract(SizeX,8,8),
bitExtract(SizeY,0,8),bitExtract(SizeY,8,8)
), -- plain pixels
nil,
false
);
elseif (BitsPerPixel == 16) or (BitsPerPixel == 24) or (BitsPerPixel == 32) then
-- to do
end
end
fileSetPos(File,PreviousPosition); -- continue reading next ICO header
end
fileClose(File);
return Icons;
end
end
end
I suppose that fileExists, fileOpen, fileClose, fileGetPos and fileSetPos are self-explanatory functions. The rest of the functions' arguments are as follows:
fileRead(file file, number bytes) - reads bytes bytes from file and returns them as a string
fileReadInteger(file file, [number bytes = 4], [bool order = true]) - reads an integer with the size of bytes bytes from file in order (little -edian = true, big-edian = false)
bitExtract(number value, number filed, number width)
dxCreateTexture(string pixels, [string format = "argb"], [bool mipmaps = true])
Here are some outputs of the function in its current state: http://i.imgur.com/dRlaoan.png
The first image is 16x16 with AND mask code commented out, second is 32x32 with AND mask code commented out, third is 16x16 with AND mask code and fourth is 32x32 with AND mask code. 8x8 and 48x48 images with AND mask code look the same as the third image in the demonstration.
ICO used for demonstration: http://lua-users.org/files/wiki_insecure/lua-std.ico

Answer 1

Thank you, #EgorSkriptunoff!
This mask is also a subject to right-padding its every line with zeroes.
This was indeed the problem. Three lines of code inside each loop solved it.
XOR mask:
if ((SizeX/PixelsPerByte)%4 ~= 0) then
fileRead(File,4-SizeX/PixelsPerByte%4);
end
AND mask:
if ((SizeX/8)%4 ~= 0) then
fileRead(File,4-SizeX/8%4);
end