Hex to Binary convert - delphi

Question

I have converted my jpeg file as HEX code through hex converter.
Now how to convert that hex to binary and save as Jpeg file on disk.
Like:
var declared as Hex code and then convert that var hex code to binary and save on disk ?
Edit:
Var
myfileHex := 'FAA4F4AAA444444'; // long as HEX code of my JPEG
function HexToBin(myfileHex): string;
begin
// Convert Hex to bin and save file as...
end;

Answer 1

Delphi already has HexToBin (Classes) procedure, since at least D5.
Try this code:
procedure HexStringToBin;
var
BinaryStream: TMemoryStream;
HexStr: AnsiString;
begin
HexStr := 'FAA4F4AAA44444';
BinaryStream := TMemoryStream.Create;
try
BinaryStream.Size := Length(HexStr) div 2;
if BinaryStream.Size > 0 then
begin
HexToBin(PAnsiChar(HexStr), BinaryStream.Memory, BinaryStream.Size);
BinaryStream.SaveToFile('c:\myfile.bin')
end;
finally
BinaryStream.Free;
end;
end;
The same could be done with any binary TStream e.g. TFileStream.

Answer 2

Hex is very easy to decode manually:
procedure HexToBin(const Hex: string; Stream: TStream);
var
B: Byte;
C: Char;
Idx, Len: Integer;
begin
Len := Length(Hex);
If Len = 0 then Exit;
If (Len mod 2) <> 0 then raise Exception.Create('bad hex length');
Idx := 1;
repeat
C := Hex[Idx];
case C of
'0'..'9': B := Byte((Ord(C) - '0') shl 4);
'A'..'F': B := Byte(((Ord(C) - 'A') + 10) shl 4);
'a'..'f': B := Byte(((Ord(C) - 'a') + 10) shl 4);
else
raise Exception.Create('bad hex data');
end;
C := Hex[Idx+1];
case C of
'0'..'9': B := B or Byte(Ord(C) - '0');
'A'..'F': B := B or Byte((Ord(C) - 'A') + 10);
'a'..'f': B := B or Byte((Ord(C) - 'a') + 10);
else
raise Exception.Create('bad hex data');
end;
Stream.WriteBuffer(B, 1);
Inc(Idx, 2);
until Idx > Len;
end;
begin
FStream := TFileStream.Create('myfile.jpg', fmCreate);
HexToBin(myFileHex, FStream);
FStream.Free;
end;