Draft Probabilistic Steganography

ProbabilisticSteganography

#define ToRadian(x) ((x) * M_PI / 180.0f)
#define ToDegree(x) ((x) * 180.0f / M_PI)
#define ToGrad(x) ((x) * M_PI / 360.0f)

static const NSString* TAG = @"main";

static NSMutableArray* visited = [NSMutableArray new];

static YACanvas *cSource = nil;


char bitsToC(vector<bool> v, int pos) {

	char r = 0;

	for(int i = 0; i <= 7; ++i) {
		if(v[i + pos] == true) {
			int s = 1 << (7 - i);
			r +=  s;
		}
	}

	return r;
}

vector<bool> cTobits(char c) {

	vector<bool> r;

	for(int i = 7; i >= 0; --i) {

		if(c & (1 << i)) {
			r.push_back(true);
		} else {
			r.push_back(false);
		}
	}

	return r;
}

int main (int argc, const char * argv[])
{

	@autoreleasepool {

		NSLog(@"Application Startup");
		
		#define variance 101
		YAVector4f *whiteBack = [[YAVector4f alloc] initVal: 1];
		YAVector2i *grid = [[YAVector2i alloc] initVals: 16 : 12 ]; // 192

		float probZero = 0.25;
		float probOne  = 0.75;

		char cryptText[] = "This is the text message.";
		int cryptTextN = 24;

		char pass[] = "Password";
		int passN = 8;


		vector<bool> textBits;

		for (int i = 0; i < cryptTextN; ++i) {
			char c = cryptText[i] ^ pass[i % passN];
			// char c = cryptText[i];
			vector<bool> charBits = cTobits(c);
			textBits.insert(textBits.end(), charBits.begin(), charBits.end());
		}


		cout << "R: " << textBits.size() << endl;


		YACanvas *cv = [[YACanvas alloc] initFile: @"original.png"];
		YACanvas *cvR = [[YACanvas alloc] initFile: result.png"];

		YAVector2i* res = cv.resolution.copy;

		YACanvas *co = [[YACanvas alloc] initResolution: res Color: whiteBack];

		int hist[variance] = {0};
		int *h = hist;
		YAVector3f *newCol = [[YAVector3f alloc] init];

		vector<bool> *tb = &textBits;

		[res sweep: ^(YAVector2i* pos){
			YAVector4f *pixel = [cv getPixel: pos];
			Color col;
			col.setRGB(pixel.x, pixel.y, pixel.z);
			float value = col.getValue();

			int valRange = int(value * float(variance));

			h[int(value * float(variance))] += 1;

			if(valRange % 2 != 0)
				valRange -= 1;

			assert(valRange >= 0);
			assert(valRange % 2 == 0);

			// calculate id
			int x = (float(pos.x) / float(res.x)) * grid.x;
			int y = (float(pos.y) / float(res.y)) * grid.y;
			int idx = y * grid.x + x;

			bool theBit = (*tb)[idx];
			int incer = 0;

			if(theBit) {
				if([YAProbability dice: probOne])
					incer = 1;
			} else {
				if([YAProbability dice: probZero])
					incer = 1;
			}

			valRange += incer;

			float newValue = float(valRange) / float(variance);
			col.setValue(newValue);

			[newCol setValues: col.getR() : col.getG() : col.getB()];
			[co setPixel: pos  Color: newCol]; 

		}];


		vector<int> rawRes(grid.x * grid.y, 0); 
		vector<int> *rR = &rawRes;

		[res sweep: ^(YAVector2i* pos){
			// YAVector4f *pixel = [co getPixel: pos];
			YAVector4f *pixel = [cvR getPixel: pos];

			int x = (float(pos.x) / float(res.x)) * grid.x;
			int y = (float(pos.y) / float(res.y)) * grid.y;
			int idx = y * grid.x + x;

			Color col;
			col.setRGB(pixel.x, pixel.y, pixel.z);

			float value = col.getValue();
			int valRange = int(value * float(variance));

			if(valRange % 2 != 0) {
				(*rR)[idx] += 1;
			}

		}];



		vector<bool> textBitsOut;
		int celSize = (res.y / grid.y) * (res.x / grid.x);

		for(auto r : rawRes) {
			float rp = float(r) / float(celSize);

			if( fabs(probZero - rp) < fabs(probOne - rp))
				textBitsOut.push_back(true);
			else
				textBitsOut.push_back(false);
		}


		for(int i = 0; i < textBits.size(); ++i) {
			cout << i << " : " << textBits[i] << " / " << textBitsOut[i] << endl; 
		}

		for(int i = 0; i < 24; ++i) {
			char c = bitsToC(textBitsOut, i * 8);  
           	c = c ^ pass[i % passN];

			char cc = cryptText[i];  
			printf("%c, %c\n", c ,cc);
		}
			cout << endl; 

		[co writePNGTo: @"result.png"];

	}
}