Hello, I have recently needed a converter to hexadecimal from colored images. This plugin is used for gray scale sprite development on the ti-84 graphing calculator. I surfed the internet and couldn't find what I needed, so I decided to write a plugin on paint.net that will process my selection and display the output. Here's my progress, it currently is functional however it is conditional. It only properly works when my selection is 8x8, i am aware that i can put it in try and catch i will for sure implement that later, I want to focus on the things that matter now.
bool done = false;
void Render(Surface dst, Surface src, Rectangle rect)
{
    Rectangle selection = EnvironmentParameters.GetSelection(src.Bounds).GetBoundsInt();
    ColorBgra CurrentPixel;
    string[,] binary1 = new string[8,8];
    string[,] binary2 = new string[8,8];
    int xx;
    int yy = 0;
    for (int y = selection.Top; y < selection.Bottom; y++)
    {
        xx=0;
        if (IsCancelRequested) return;
        for (int x = selection.Left; x < selection.Right;x++)
        {
            CurrentPixel = src[x,y];
            int rgb = (CurrentPixel.R+CurrentPixel.G+CurrentPixel.B)/3;
            if(rgb >= 0 && rgb < 64)
            {
                binary1[xx,yy] = "1";
                binary2[xx,yy] = "1";
            }
            else if(rgb >= 64 && rgb < 128)
            {
                binary1[xx,yy] = "1";
                binary2[xx,yy] = "0";
            }
            else if(rgb >= 128 && rgb < 192)
            {
                binary1[xx,yy] = "0";
                binary2[xx,yy] = "1";
            }
            else if(rgb >= 192 && rgb < 256)
            {
                binary1[xx,yy] = "0";
                binary2[xx,yy] = "0";
            }
            dst[x,y] = CurrentPixel;
            xx++;
        }
        yy++;
    }
    if(done == false)
    {
        string line;
        string hex = "[";
        for(int y = 0; y < 8; y++)
        {
            line = "";
            for(int x = 0; x < 8; x++)
                line += binary1[x,y];
            hex += ConvertHex(line);
        }
        hex += "][";
        for(int y = 0; y < 8; y++)
        {
            line = "";
            for(int x = 0; x < 8; x++)
                line += binary2[x,y];
            hex += ConvertHex(line);
        }
        hex += "]";
        System.IO.File.WriteAllText(@"C:\Users\user\Desktop\Dota Duelz\hex.txt", hex);
        done = true;
    }
}

string ConvertHex(string strBinary)
{
    string hex = Convert.ToInt32(strBinary,2).ToString("X");
    if(hex.Length == 1)
        hex = "0" + hex;
    return hex;
}
Keep in mind this is the first plugin i write on paint.net, so it probably isn't the most efficient way to do this. Now my question is: what is a good way to display the output string "hex" to the user? I am currently writing to a file. Coming from java development I don't know the tools i can use to do these operations. I tried to display a message box but it seems to open it 8 times and that's why i tried implementing the Boolean done so i make sure it runs only once, but i am not sure why it didn't work.

visual example of what it does:

It starts with the first image, i have to manually select 8 x 8 pixels and run the program to generate these four pairs hexs
[04050B3434742EEC][070E1A3B166E655B]
[20F0782C0A1E3577][E0A090BC3E34771E]
[5455D4F4CA5F7B00][F9FAF3CFFD6E6A00]
[1B9B1B3733FBFE00][0E2FFF5B777B3200]
and using this website, I am able to see the images visually
http://clrhome.org/pix/

This is a very useful tool that I might start using.  The inconvenient part thou is that it runs on a PC, while the rest of the code is [probably, at least for me) on a calculator. 
Also, your algorithem to convert pixels to hex seems a bit inconvenient. Idk what is realy going on here (always was a java person and never worked with the PDN API), but I will see if I can try to optimize some of the plugin.
Edit:
Here is an optimized version of the plugin. I know the algorithm is error free because i use it in a small pixel to hex converter on my calc, however it might contain syntex errors.
bool done = false;
void Render(Surface dst, Surface src, Rectangle rect)
{
    Rectangle selection = EnvironmentParameters.GetSelection(src.Bounds).GetBoundsInt();
    ColorBgra CurrentPixel;
    int itr = 3;
    string hex1;
    string hex2;
    string hexi = "0123456789ABCDEF";
    int tempInt1;
    int tempInt2;
    for (int y = selection.Top; y < selection.Bottom; y++)
    {
        if (IsCancelRequested) return;
        for (int x = selection.Left; x < selection.Right;x++)
        {
            CurrentPixel = src[x,y];
            int rgb = 4-((CurrentPixel.R+CurrentPixel.G+CurrentPixel.B)/192);
            if(rgb>1){
tempInt1+= Math.pow(2,itr)
    }
            if(rgb==1||rgb==3){
tempInt2+= Math.pow(2,itr)
            }
    if(itr == 0){
irt = 3;
hex1 += hexi[tempInt1];
                hex2 += hexi[tempInt2];
  temp1 = 0;
temp2 = 0;
            }
            itr--;
        }
    }
    if(done == false)
    {
        System.IO.File.WriteAllText(@"C:\Users\user\Desktop\Dota Duelz\hex.txt", "["+hex1+" "+hex2+"]");
        done = true;
    }
}
And here is a more optimized version, has less of a chance of working then first version, remember that none of this is actually tested. :p
bool done = false;
void Render(Surface dst, Surface src, Rectangle rect)
{
    Rectangle selection = EnvironmentParameters.GetSelection(src.Bounds).GetBoundsInt();
    ColorBgra CurrentPixel;
    int itr = 3;
    string hex1;
    string hex2;
    string hexi = "FEDCBA9876543210";
    byte temp1;
    byte temp2;
    for (int y = selection.Top; y < selection.Bottom; y++)
    {
        if (IsCancelRequested) return;
        for (int x = selection.Left; x < selection.Right;x++)
        {
            CurrentPixel = src[x,y];
            byte rgb = (CurrentPixel.R+CurrentPixel.G+CurrentPixel.B)/192;
      temp1=((rgb >> 1) + temp1) *2; //might have to change to temp1=((rgb & 2 >> 1) + temp1) *2;
      temp2=((rgb & 1 )+ temp2) *2;
    if(itr == 0){
irt = 3;
hex1 += hexi[temp1];
                hex2 += hexi[temp2];
  tempInt1 = 0;
tempInt2 = 0;
            }
            itr--;
        }
    }
    if(done == false)
    {
        System.IO.File.WriteAllText(@"C:\Users\user\Desktop\Dota Duelz\hex.txt", "["+hex1+" "+hex2+"]");
        done = true;
    }
}


Can you actualy try to run my actual code? I dont have a C# compiler and was doing stuff with my knolage of java. 
I have become interested if it will actually work, and if it does work if the output would is correct, or if it is perhaps inverted or a shade off. If the code actually works i can explain it to you later. 

Hmm thats weird. Can i see what you are trying to convert? Also to get your format just replace the spaces between the hexes with a "][".  And it does not work with spaces bigger then 8*8, its not ment to.