Steganography.txt

function crop(image,width,height){
    var croppedimg = new SimpleImage(width,height);
    for(var pixel of image.values()){
        var x = pixel.getX();
        var y = pixel.getY();
        if(x<width && y<height){
            var np = croppedimg.getPixel(x,y);
            np.setRed(pixel.getRed());
            np.setGreen(pixel.getGreen());
            np.setBlue(pixel.getBlue());
        }
    }
    return croppedimg;
}



function clearbits(pixel){
    pixel = Math.floor(pixel/16)*16;
    return pixel;
}

function chop2hide(image){
    for(var pixel of image.values()){
        pixel.setRed(clearbits(pixel.getRed()));
        pixel.setGreen(clearbits(pixel.getGreen()));
        pixel.setBlue(clearbits(pixel.getBlue()));
    }
    return image;
}

function shift(image){
    for(var pixel of image.values()){
        pixel.setRed(pixel.getRed()/16);
        pixel.setGreen(pixel.getGreen()/16);
        pixel.setBlue(pixel.getBlue()/16);
    }
    return image;
}

function combineCheck(p,q){
    var ans = p+q;
    if(ans>255){
        print("Error: Answer too big");
    }
    return ans;
}

function combine(start,hide){
    var finalimg = new SimpleImage(start.getWidth(),start.getHeight());
    for(var pixel of finalimg.values()){
        var x = pixel.getX();
        var y = pixel.getY();
        
        var startpixel = start.getPixel(x,y);
        var hidepixel = hide.getPixel(x,y);
        
        pixel.setRed(combineCheck(startpixel.getRed(),hidepixel.getRed()));
        pixel.setGreen(combineCheck(startpixel.getGreen(),hidepixel.getGreen()));
        pixel.setBlue(combineCheck(startpixel.getBlue(),hidepixel.getBlue()));
    }
    return finalimg;
}

function decryption(value){
    value = Math.floor(value%16)*16;
    return value;
}

function extraction(image){
    var result = new SimpleImage(image.getWidth(),image.getHeight());
    for(var pixel of result.values()){
        var x = pixel.getX();
        var y = pixel.getY();
        var imagepixel = image.getPixel(x,y);
        
        pixel.setRed(decryption(imagepixel.getRed()));
        pixel.setGreen(decryption(imagepixel.getGreen()));
        pixel.setBlue(decryption(imagepixel.getBlue()));
    }
    return result;
}

var start = new SimpleImage("astrachan.jpg");
print("Original image:",start);
var hide = new SimpleImage("hilton.jpg");
print("Image to hide:",hide);

var cropWidth = start.getWidth();
if(hide.getWidth() < cropWidth){
    cropWidth = hide.getWidth();
}

var cropHeight = start.getHeight();
if(hide.getHeight() < cropHeight){
    cropHeight = hide.getHeight();
}

start = crop(start, cropWidth, cropHeight);
print("Cropped Original Image:",start);
hide = crop(hide, cropWidth, cropHeight);
print("Cropped Image to Hide:",hide);

start = chop2hide(start);
hide = shift(hide);

var msg = combine(start,hide);
print("Altered Orignal Image:",msg);
var decrypt = extraction(msg);
print("Extracted Image:",decrypt);