[pngpp-devel] Steganographic in PNG

[Sebastian Camjayi]

Hi people, i have a problem and maybe you can help me...
I use the library to Hide one message in the image.

For each color component, I set, in the LSB ( Less Significant Bit ) , one bit of the message.
For example:

void PngRGB::Hide(Space* space, Message* msg)
{
    png::image<png::rgb_pixel> imageRGB(space->GetFilePath());
    fstream fdata(msg->GetFilePath());
    long hideBytes = 0;
    fdata.seekg(msg->GetHiddenSize());

    while(!fdata.eof() && (hideBytes < spaceSize))
    {
        fdata.read(&dataByte,sizeof(char));

        //For each byte of the message, hide in the image components
        for(int k=0;k<8;k++)
        {
            //I get the color component of the current pixel (pixel.red, pixel.green, pixel.blue)
            // pixel = image[x][y];
            png::byte imgByte = GetColorComponent(imageRGB);

            //I set one bit of the messege byte in the Less Significant Bit 
            imgByte = (imgByte & ~1) | ((dataByte>>(7-k))&1);
            
            // image[x][y] = pixel;
            SetNewColorComponentInCurrentPixelCoord(imageRGB ,imgByte); 
            
            //Increment color component (if red then now is green) 
            IncColorComponent(CurrentColorComponent);
            
            //Move to the next pixel.
            if(CurrentColorComponent == Red)
                IncCurrentPixelPosition(imageRGB);
        }
        hideBytes++;
    }
    imageRGB.write(space->GetFilePath());
    msg->IncHiddenSize(hideBytes);
    
    fdata.close();
}

Questions:

1) Someone knows a better way to do this?. maybe without access to each pixel.
2) If I write the image with the write function, Will i be able to access the bits hidden in the picture?
3) Can i write in the same path where i am reading?
4) Why the saved image has a size larger than the original?? I need always to the saved image is less than or equal to the original. Theoretically if I change just a bit, why would it expand the original image?.

Thanks
Sebastian.