Basic Image Asset Protection

I little while ago I was working on an image format to help protect my art assets in T2D before it became MIT. I had plans to, at some point, add it to T3D and I have finally gotten around to it.

I wanted a personal image format that no one else had, one that's simple but offers some level of protection. I would have loved to implement compression with this, but is way beyond my skill level.

The general idea is to use a format similar to a BMP image. The FX1 format is uncompressed and has 4 bytes per pixel, supporting ARGB. Really, the only difference between my FX1 format and a BMP is:

* One extra byte per pixel to support alpha
* Every byte of image data is "offset" or "skewed" using a simple XOR bitwise operation

The image header is only 12 bytes long and the structure is as follows:
U8: 0x88 "^"
U8: 0x46 "F"
U8: 0x58 "X"
U8: 0x31 "1"
U16: Width
U16: Height
U8: Blue Offset
U8: Green Offset
U8: Red Offset
U8: Alpha Offset

While the offsets are stored in the header, you could nix RGBA offsets and hard code them in the engine source to make it that much harder to decode the image.

Here's the C code for the new image format. Place this under: Engine > gfx > bitmap > loaders > bitmapFX1.cpp

You can also find the files here: www.torchive.com/custom/fx1/. Including a C# WinForms encoder application zipped up and ready to go (Used the .NET 4.5 Framework.)

#include "core/stream/stream.h"

#include "gfx/bitmap/gBitmap.h"


static bool sReadFX1(Stream &stream, GBitmap *bitmap);
static bool sWriteFX1(GBitmap *bitmap, Stream &stream, U32 compressionLevel);

static struct _privateRegisterBMP
{
   _privateRegisterBMP()
   {
      GBitmap::Registration reg;

      reg.extensions.push_back( "fx1" );

      reg.readFunc = sReadFX1;
      //reg.writeFunc = sWriteFX1; // No write function yet, though very similar to the read function, it can be added.

      GBitmap::sRegisterFormat( reg );
   }
} sStaticRegisterBMP;


// fx1 header format containing identifier and ARGB byte offset values

struct FX1FILEHEADER
{
   U8 Identifier[4];
   U16 Width;
   U16 Height;
   U8  B;
   U8  G;
   U8  R;
   U8  A;
};

//------------------------------------------------------------------------------
//-------------------------------------- Supplementary I/O (Partially located in
//                                                          bitmapPng.cc)
//

static bool sReadFX1(Stream &stream, GBitmap *bitmap)
{
   FX1FILEHEADER  fx;
   GFXFormat fmt = GFXFormatR8G8B8A8;

   // Read the file header for the format identifier, the size of the image and the RGBA offsets
   stream.read(4, &fx.Identifier);
   stream.read(&fx.Width);
   stream.read(&fx.Height);
   stream.read(&fx.B);
   stream.read(&fx.G);
   stream.read(&fx.R);
   stream.read(&fx.A);

   bitmap->allocateBitmap(fx.Width, fx.Height, false, fmt);
   U32   width  = bitmap->getWidth();
   U32   height = bitmap->getHeight();
   U8 *ptr = bitmap->getAddress(0, 0);

   // There maybe a better way to do this than a nested for loop
   // such as for (U32 i = (height * width) yadda yadda, or _asm... 
   // but this works and is fast enough, at least for me
   for (U32 y = 0; y < height; y++)
   {
      for (U32 x = 0; x < width; x++)
	  {
         // FX1 uses 4 bytes per pixel, RGBA (GFXFormatR8G8B8A8)
         U8 pixel[4];
         
         // Read 4 bytes into an array for processing
		 stream.read(4, &pixel);

         // Files read as BGRA
		 ptr[0] = (pixel[0] ^ fx.B); // Restore Blue value
         ptr[1] = (pixel[1] ^ fx.G); // Restore Green value
		 ptr[2] = (pixel[2] ^ fx.R); // Restore Red value
         ptr[3] = (pixel[3] ^ fx.A); // Restore Alpha value
         
         // Add 4 bytes to move on to the next pixel
		 ptr += 4;
      }
   }

   bitmap->setHasTransparency(true);

   return true;
}

/*
// Empty write shell if you want to implement a write function
static bool sWriteFX1(GBitmap *bitmap, Stream &stream, U32 compressionLevel)
{
   TORQUE_UNUSED( compressionLevel );  // FX1 does not use compression
}
*/

And now, just need to alter 3 TorqueScript files:

FILE: /game/core/scripts/client/postFx/postFxManager.gui.cs
LINE: 382-ish

function ppColorCorrection_selectFile()
{
   %filter = "Image Files (*.png, *.jpg, *.dds, *.bmp, *.gif, *.jng, *.tga, *.fx1)|*.png;*.jpg;*.dds;*.bmp;*.gif;*.jng;*.tga;*.fx1|All Files (*.*)|*.*|";   
   getLoadFilename( %filter, "ppColorCorrection_selectFileHandler");
}

==========================================================================================

FILE: /game/scripts/gui/chooseLevelDlg.cs
LINE: 121-ish

// Test against all of the different image formats
// This should probably be moved into an engine function
if (isFile(%levelPreview @ ".png") ||
    isFile(%levelPreview @ ".jpg") ||
    isFile(%levelPreview @ ".bmp") ||
    isFile(%levelPreview @ ".gif") ||
    isFile(%levelPreview @ ".jng") ||
    isFile(%levelPreview @ ".mng") ||
    isFile(%levelPreview @ ".tga") ||
    isFile(%levelPreview @ ".fx1"))
{
   %preview.setBitmap(%levelPreview);
}

==========================================================================================

FILE: /game/tools/materialEditor/main.cs
LINE: 90-ish

MaterialEditorGui.fileSpec = "Torque Material Files (materials.cs)|materials.cs|All Files (*.*)|*.*|";
MaterialEditorGui.textureFormats = "Image Files (*.png, *.jpg, *.dds, *.bmp, *.gif, *.jng, *.tga, *.fx1)|*.png;*.jpg;*.dds;*.bmp;*.gif;*.jng;*.tga;*.fx1|All Files (*.*)|*.*|";