//btnDecrypt Click Event starting the decryption
private void btnDecrypt_Click(object sender, EventArgs e)
{
txtBxDecrypt.Text = "";
OpenFileDialog curDialog = new OpenFileDialog();
if (curDialog.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
using (Bitmap curBitmap = curIO.fileValidImage(curDialog.FileName))
{
if (curBitmap != null)
{
Decrypting curDecrypting = new Decrypting((Color)cmbBxDecryptStart.SelectedItem, curBitmap, curIO, (int)numUpDwnDecrypt.Value);
if (!curDecrypting.errors)
{
txtBxDecrypt.Text = curDecrypting.decryptedString;
}
else
{
displayError("Either the input parameters or the image are wrong.", curDecrypting.errorMessage, false);
}
}
else displayError("Please, selected a valid image file.", null, false);
}
}
}
public Point startPixelOrig; //Stores the "fake start point", relevant while analysing the next pixels storing length information
#endregion Fields
#region Constructors
//---
//Starting actions on account of the given process (encryption/decription)
public Hashing(Color temp_startColor, Encrypting curEncrypting, Decrypting curDecrypting, IO temp_curIO)
{
startColor = temp_startColor;
curIO = temp_curIO;
curColors = new List<Color>(curIO.allKnownColors);
startOffset = new startOffsetInfo();
if (curEncrypting != null)
{
if (curEncrypting.origText == null || curEncrypting.origText.Length < 1)
{
errors = true;
return;
}
curLength = curEncrypting.origText.Length + 2 + (curEncrypting.origText.Length + 2).ToString().Length; //Length considered while decrypting
encryptingNumber = curEncrypting.encryptingNumber;
}
else
{
if (curDecrypting.origBitmap == null)
{
errorMessage = "There was a problem while accessing the image file.";
errors = true;
return;
}
encryptingNumber = curDecrypting.encryptingNumber;
pixelsToIgnore = new List<Point>();
//Preliminary validity check by looking for the startColor (in the right position) and determining the length (and the offset, if applicable)
curIO.getBoundaryPixels(curDecrypting, this);
if (curLength <= 0)
{
errors = true;
return;
}
}
calculateStartStep(); //Calculating curStep
buildCharsVsColors(); //Building the hash table (dictionary with all the accounted characters and their equivalent color) which will be used in the current encryption/decryption process
if (curDecrypting != null)
{
//For decryption. Confirming that the length value, calculated above, matches the information in the pixels enconding the actual length.
//The reason for not having this analysis before is the fact that the charsVsColors is required
if (!curIO.lengthIsOK(curDecrypting, this)) this.errors = true;
}
}
//There is an offset and thus the actual start of the encrypted chunk is certain; but this determination is not evident as far as it is stored as an integer (= distance).
//This integer has to be converted into actual pixel/point position; this is what this function does: returning the actual start point by bringing the offset into account
private Point newStartFromOffset(Point curStart, int offSet, Decrypting curDecrypting)
{
Point newStart = new Point();
int curCount = 0;
bool firstTime = true;
for (int x = curDecrypting.origBitmap.Width - 1; x >= 0; x--)
{
for (int y = curDecrypting.origBitmap.Height - 1; y >= 0; y--)
{
if (firstTime)
{
x = curStart.X;
y = curStart.Y;
firstTime = false;
}
curCount = curCount + 1;
if (curCount > offSet)
{
newStart.X = x;
newStart.Y = y;
break;
}
}
if (curCount >= offSet) break;
}
return newStart;
}
//Last check performed while hashing (for decryption): the previously-calculated length has to match the value encrypted in some of the pixels of the image in order
//to confirm that this is a right image and to go ahead with the decryption
public bool lengthIsOK(Decrypting curDecrypting, Hashing curHashing)
{
bool isOK = true;
curHashing.pixelsLength = new pixelsLengthInfo();
int count = -1;
int calcLength = 0;
string lengthString = "";
bool firstTime = true;
bool foundStart = false;
int startVal = 1;
if (curHashing.startOffset.startOffsetCount > -1) startVal = startVal + 1; //"After pixel" of the offSet has also to be skipped
for (int x = 0; x < curDecrypting.origBitmap.Width; x++)
{
for (int y = 0; y < curDecrypting.origBitmap.Height; y++)
{
if (firstTime)
{
x = curHashing.startPixelOrig.X;
y = curHashing.startPixelOrig.Y;
firstTime = false;
}
count = count + 1;
if (count >= startVal) //to skip startColor and, eventually, offset after pixel
{
Color curColor = curDecrypting.origBitmap.GetPixel(x, y);
KeyValuePair<char, Color> tempPair = curHashing.charsVsColors.FirstOrDefault(x2 => twoColorsAreEqual(x2.Value, curColor));
if (Char.IsDigit(tempPair.Key))
{
curHashing.pixelsToIgnore.Add(new Point(x, y));
lengthString = lengthString + tempPair.Key.ToString();
if (!foundStart)
{
curHashing.pixelsLength.startPixel = new Point(x, y);
foundStart = true;
}
}
else
{
return false;
}
if (int.TryParse(lengthString, out calcLength))
{
if (calcLength == curHashing.curLength)
{
curHashing.pixelsLength.length = calcLength;
curHashing.pixelsLength.endPixel = new Point(x, y);
return true;
}
}
else return false;
}
}
}
return isOK;
}
//--------------------
//------------------------------- DECRYPTING
//Method call soon in the hashing (for decrypting) process: it does not only extract valuable information (start pixel, length and, eventually, offset),
//but also avoids any wrong image to be analysed further.
public void getBoundaryPixels(Decrypting curDecrypting, Hashing curHashing)
{
Point tempLast = new Point(-1, -1);
int tempLength = -1;
int lastLength = 0;
Color nextPixel = new Color();
bool storeNext = false;
curHashing.curLength = -1;
for (int x = 0; x < curDecrypting.origBitmap.Width; x++)
{
for (int y = 0; y < curDecrypting.origBitmap.Height; y++)
{
if (tempLength >= 0) tempLength = tempLength + 1;
Color curColor = curDecrypting.origBitmap.GetPixel(x, y);
if (storeNext)
{
//This is the "after pixel" which confirms that an offset actually exists
if (!twoColorsAreEqual(curColor, curHashing.startColor)) nextPixel = curColor;
storeNext = false;
}
//StartColor determines where the "relevant chunk" starts/ends, what is done by this condition
if (twoColorsAreEqual(curColor, curHashing.startColor))
{
if (tempLength < 0)
{
curHashing.startPixel = new Point(x, y);
curHashing.startPixelOrig = new Point(x, y);
storeNext = true;
tempLength = 0;
}
else
{
tempLast = new Point(x, y);
lastLength = tempLength;
}
}
}
}
if (tempLast != new Point(-1, -1) && lastLength > 0)
{
//The collected information seems right
curHashing.endPixel = new Point(tempLast.X, tempLast.Y);
curHashing.curLength = lastLength + 1;
int afterIndex = curHashing.curIO.allKnownColors.IndexOf(curHashing.startColor) + curDecrypting.encryptingNumber;
if (afterIndex > curHashing.curIO.allKnownColors.Count - 1) afterIndex = curDecrypting.encryptingNumber;
Color afterOffset = curHashing.curIO.allKnownColors[afterIndex];
bool analyseOffset = !nextPixel.IsEmpty && twoColorsAreEqual(afterOffset, nextPixel);
if (analyseOffset)
{
//There is an offset and thus some variables have to be updated
curHashing.curLength = curHashing.curLength - 1; //afterOffset is not included withing the length value
curHashing.startOffset.afterOffset = afterOffset;
curHashing.startOffset.startOffsetCount = curDecrypting.encryptingNumber;
curHashing.startOffset.startPoint = new Point(curHashing.startPixel.X, curHashing.startPixel.Y);
curHashing.curLength = curHashing.curLength + curHashing.startOffset.startOffsetCount;
curHashing.startPixel = newStartFromOffset(curHashing.startPixel, curHashing.startOffset.startOffsetCount, curDecrypting);
}
lengthCorrection(curHashing);
}
}
//Final stage of the decryption process: application of all the previous calculations to the image to extract the encrypted message
public Decrypting decryptImage(Decrypting curDecrypting)
{
Bitmap curBitmap = curDecrypting.origBitmap;
curDecrypting.decryptedString = "";
Hashing curHashing = curDecrypting.curHashing;
bool origFound = false;
bool firstTime = true;
bool decryptColor = false;
for (int x = 0; x < curDecrypting.origBitmap.Width; x++) //The analysis starts from the startPixel, already calculated while creating the Hash table
{
for (int y = 0; y < curDecrypting.origBitmap.Height; y++)
{
bool analyseStart = false;
bool goAhead = false;
if (firstTime)
{
x = curDecrypting.curHashing.startPixel.X;
y = curDecrypting.curHashing.startPixel.Y;
}
Color curColor = curDecrypting.origBitmap.GetPixel(x, y);
if (firstTime)
{
if (curHashing.startOffset.startOffsetCount == -1) //No offset
{
analyseStart = true;
}
else decryptColor = true;
firstTime = false;
}
else if (curHashing.startOffset.startOffsetCount != -1) //Offset
{
if (!origFound && twoColorsAreEqual(curColor, curHashing.startColor))
{
analyseStart = true;
}
}
if (analyseStart)
{
//No offset and thus the restrictions in the conversions start already here
if (!twoColorsAreEqual(curDecrypting.origBitmap.GetPixel(x, y), curHashing.startColor))
{
curDecrypting.errors = true;
return curDecrypting;
}
else
{
decryptColor = false;
}
}
if (decryptColor)
{
//The original start point hasn't either be found or was found and all the surrounding, irrelevant information has already been skipped
if (x == curHashing.endPixel.X && y == curHashing.endPixel.Y)
{
return curDecrypting;
}
goAhead = true;
}
else
{
if (!origFound)
{
if (x == curHashing.pixelsLength.endPixel.X && y == curHashing.pixelsLength.endPixel.Y)
{
origFound = true;
decryptColor = true; //from the next pixel onwards, all the information should be decrypted
}
}
else
{
curDecrypting.errors = true;
return curDecrypting;
}
}
if (goAhead)
{
KeyValuePair<char, Color> tempPair = curHashing.charsVsColors.FirstOrDefault(x2 => twoColorsAreEqual(x2.Value, curColor));
if (tempPair.Value.IsEmpty && !twoColorsAreEqual(curColor, curHashing.startColor))
{
bool isOK = false;
if (curDecrypting.encryptingNumber > 0)
{
if (!curHashing.replacePair.Value.IsEmpty && twoColorsAreEqual(curColor, curHashing.replacePair.Value))
{
tempPair = new KeyValuePair<char, Color>(curHashing.replacePair.Key, curColor);
isOK = true;
}
else if (!curHashing.startOffset.replaceAfter.Value.IsEmpty && twoColorsAreEqual(curColor, curHashing.startOffset.replaceAfter.Value))
{
tempPair = new KeyValuePair<char, Color>(curHashing.startOffset.replaceAfter.Key, curColor);
isOK = true;
}
}
if (!isOK)
{
curDecrypting.errors = true;
return curDecrypting;
}
}
curDecrypting.decryptedString = curDecrypting.decryptedString + tempPair.Key.ToString();
}
}
}
return curDecrypting;
}
