.ZNG image file format

i have try this code and you are right, the program loop forever. The function xor seem to be the cause of the problem.

I see that you XOR a string with a key, but a png file is
a binary file? Maybe you must xor with bytes and not with
string.

Example :
'read bank data to buffer string
Local buffer$
For i = 0 To bank.size()-1
Local b:Byte = PeekByte(bank,i)
buffer :+ Chr$(b)
Next

Must be IMO:

'read bank data
For i = 0 To bank.size()-1
Local b:Byte = PeekByte(bank,i)

' Xor the byte with one char of the key
' then write the char generated by the xor
Next


xlsior : You are right, Chroma you need to compress the file before encrypting.

'.ZNG ImageLoader

'Author: Noel Cole (Chroma)
'Email:  noel@...

Global ZNG_Key$
ZNG_Key$ ="abc123"

SetZNGKey("abc123")

Local inFile$ = "Fond Deviant Art_00009.png"
Local outFile$ = StripExt(inFile)

Local ibank:TBank = LoadBank(inFile)

' De activate this function made loop forever?
'If ZNG_Key Then ibank = XorBank(ibank,ZNG_Key)
Local cbank:TBank = CompressBank(ibank)

Local out:TStream = WriteFile(outFile + ".zng")
out.writebytes(cbank.buf(), cbank.size())
CloseStream(out)
End



Graphics 800,600

Local img:TImage = LoadImageZNG("Fond Deviant Art_00009.zng")

SetBlend ALPHABLEND

SetClsColor 100,100,100

While Not KeyHit(KEY_ESCAPE)
Cls

DrawImage img,100,100


Flip
Wend
End




'And here's the ZNG_Converter again with the encryption option:

'Zipped Network Graphic [.zng] - Image File Format Converter

'Encryption Supported

'Build into an .exe and drag and drop your image files to convert them to .zng

'by Noel Cole (Chroma)

Function XorBank:TBank(bank:TBank, key$)
	'read bank data to buffer string
	Local buffer$
	For i = 0 To bank.size()-1
		Local b:Byte = PeekByte(bank,i)
		buffer :+ Chr$(b)
	Next
	
	buffer = xor(buffer,key$)

	Local rbank:TBank = CreateBank(buffer.length)
	For i = 0 To rbank.size()-1
		PokeByte(rbank,i,Asc(Mid$(buffer,i+1,1)))
	Next
	Return rbank
End Function

Function xor:String(str$, key$)
	Local ml%, pl%, i%, result$
	ml% = Len(str)
	pl% = Len(key)
	For i = 0 Until ml
		Local c:Byte = str$[i]
		Local k = key$[i Mod pl]
		c = c ~ k
		result$ :+ Chr(c)
	Next 
	Return result$
EndFunction

Function CompressBank:TBank( bank:TBank )
	Local size=bank.Size()
	Local out_size=size+size/10+32
	Local out:TBank=TBank.Create( out_size )
	compress out.Buf()+4,out_size,bank.Buf(),size
	out.PokeByte 0,size
	out.PokeByte 1,size Shr 8
	out.PokeByte 2,size Shr 16
	out.PokeByte 3,size Shr 24
	out.Resize out_size+4
	Return out
End Function




Function LoadImageZNG:TImage(zngFile$, flags%=-1)
	Local cbank:TBank = LoadBank(zngFile)
	Local ubank:TBank = UncompressBank(cbank)
	If ZNG_Key Then ubank = XorBank(ubank,ZNG_Key)
	Return LoadImage(ubank, flags)
End Function

Function LoadPixmapZNG:TPixmap(zngFile$)
	Local cbank:TBank = LoadBank(zngFile)
	Local ubank:TBank = UncompressBank(cbank)
	Return LoadPixmap(ubank)
End Function




Function UncompressBank:TBank( bank:TBank )
	Local out_size
	out_size:|bank.PeekByte(0)
	out_size:|bank.PeekByte(1) Shl 8
	out_size:|bank.PeekByte(2) Shl 16
	out_size:|bank.PeekByte(3) Shl 24
	Local out:TBank=TBank.Create( out_size )
	uncompress out.Buf(),out_size,bank.Buf()+4,bank.Size()-4
	Return out
End Function

Function SetZNGKey(key$)
	ZNG_Key = key
End Function