Why am I having trouble writing a pixel to a picturebox in Visual C#?

Question

I am writing an emulator program, and the virtual display is supposed to be able to take in 3 bytes of color data and display the correct color pixel, similar to how a real screen works. But when I set up some scroll bars to test the generation of pixels nothing happens. Here is my code and a screenshot of the form:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;




namespace TSC_Multi_System_Emulator
{

    public partial class Form1 : Form
    {
        private PictureBox Display = new PictureBox();
        string @emulationfolderpath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
        Bitmap screen = new Bitmap(@Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) + @"\Resource_Folder\" + @"FirstFrame.bmp");
        int x = 0;
        int y = 0;

        public Form1()
        {
            InitializeComponent();

        }
        private void Form1_Load(object sender, System.EventArgs e) {
            // Dock the PictureBox to the form and set its background to black.
            Display.BackColor = Color.Black;
            // Connect the Paint event of the PictureBox to the event handler method.

            // Add the PictureBox control to the Form. 
            this.Controls.Add(Display);


        }
        public void DigitalGraphicsDisplay(int red, int green, int blue) {
            Graphics g = Display.CreateGraphics(); 
            screen.SetPixel(x, y, Color.FromArgb(red, green, blue));
            g.DrawImage(screen, 0, 0, screen.Width, screen.Height);
            g.Save();
            if (x < screen.Width)
            {
                x = x + 1;
            }
            else if (x == screen.Width)
            {
                x = 0;
                if (y < screen.Height)
                {
                    y = y + 1;
                }
                else if (y == screen.Height)
                {
                    y = 0;
                }
            }
        }



        private void button1_Click(object sender, EventArgs e){
            int rchannel = redControl.Value;
            int gchannel = greenControl.Value;
            int bchannel = blueControl.Value;             
            DigitalGraphicsDisplay(rchannel, gchannel, bchannel);
        }




    }
}

UPDATE:

The code is now working somewhat, but I can't test the code using just a test button. I had to use the exact code given to me in the first answer, which only displayed a gradient, I wonder what I am doing wrong... :(

public partial class Form1 : Form
{

    string @emulationfolderpath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
    Bitmap screen = new Bitmap(@Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) + @"\Resource_Folder\" + @"FirstFrame.bmp");
    int x = 0;
    int y = 0;

    public Form1()
    {
        InitializeComponent();

    }
    private void Form1_Load(object sender, System.EventArgs e) {
        // Dock the PictureBox to the form and set its background to black.
        Display.BackColor = Color.Black;
        // Connect the Paint event of the PictureBox to the event handler method.

        // Add the PictureBox control to the Form. 
        this.Controls.Add(Display);


    }

    public void DigitalGraphicsDisplay(int red, int green, int blue)
    {
        if (Display.Image == null)
        {
            Bitmap NewBMP = new Bitmap(Display.ClientRectangle.Width, Display.ClientRectangle.Height);
            using (Graphics g = Graphics.FromImage(NewBMP))
            {
                g.Clear(Color.White);
            }
            Display.Image = NewBMP;
        }

        (Display.Image as Bitmap).SetPixel(x, y, Color.FromArgb(red, green, blue));

        Display.Invalidate();

        x++;

        if (x >= Display.Image.Width)
        {
            x = 0;
            y++;

            if (y >= Display.Image.Height)
            {
                y = 0;
            }
        }
    }


    private void button1_Click(object sender, EventArgs e){
        Boolean a = false;
        int b = 0;
        do
        {
            DigitalGraphicsDisplay(51, 153, 102);
            if (b == 10000)
            {
                a = true;
            }
            b = b + 1;
        } while (a);

    }





}

}

All I am getting is a white picturebox with nothing else in it... (The gradient code did work though)

Answer 1

It looks like you are trying to draw directly on the PictureBox control itself.

Instead you should have an Image assigned to the PictureBox and then draw on the image.

Try changing your code as shown below. (Including the click event for testing.)
Note, the PictureBox keeps the reference to the image directly so you don't need a separate screen image in your class, unless you have a different purpose for it.

Also, this uses Bitmap.SetPixel() which is an extremely slow way to set pixels. There is a much faster but slightly more complex way, in these other links:

• SetPixel is too slow. Is there a faster way to draw to bitmap?
• Work with bitmaps faster in C#

Remember your button click will only draw one pixel at a time.
So be sure to look carefully:

Running my test code within the click event will yield this:

int x = 0;
int y = 0;
public void DigitalGraphicsDisplay(int red, int green, int blue)
{
    if (Display.Image == null)
    {
        Bitmap NewBMP = new Bitmap(Display.ClientRectangle.Width, Display.ClientRectangle.Height);
        using (Graphics g = Graphics.FromImage(NewBMP))
        {
            g.Clear(Color.White);
        }
        Display.Image = NewBMP;
    }

    (Display.Image as Bitmap).SetPixel(x, y, Color.FromArgb(red, green, blue));

    Display.Invalidate();

    x++;

    if (x >= Display.Image.Width)
    {
        x = 0;
        y++;

        if (y >= Display.Image.Height)
        {
            y = 0;
        }
    }
}

private void button1_Click(object sender, EventArgs e)
{
    // Temporary code to show that it works (Due to Bitmap.SetPixel() it will be slow)
    for (int I = 1; I < Display.ClientRectangle.Width * Display.ClientRectangle.Height; I++)
        DigitalGraphicsDisplay((I/255)%255, (I % Display.ClientRectangle.Width) % 255, 127);
}

---

UPDATE: Per your comment, try this sample code:

private void button1_Click(object sender, EventArgs e)
{ 
    Boolean a = true; 
    int b = 0; 
    do
    { 
        DigitalGraphicsDisplay(51, 153, 102); 

        if (b == 10000) 
        {
            a = false;
        } 

        b = b + 1; 
    } while (a); 
}

Answer 2

    public void DigitalGraphicsDisplay(int red, int green, int blue) {
        Graphics g = Display.CreateGraphics(); 
        screen.SetPixel(x, y, Color.FromArgb(red, green, blue));
        g.DrawImage(screen, 0, 0, screen.Width, screen.Height);
        g.Save();

All possible mistakes in one go..

• Never use CreateGraphics to draw persistent Graphics! Always either go for the Paint event or draw into the Image.

• Graphics.Save does not save any drawn pixels. It saves the state of the Graphics object, which does not contain graphics but is a tool to write into a related bitmap. The state includes scale, rotation, smoothing-mode and then some..

You already write into the Bitmap so you can simply make it your new PictureBox.Image..

Or the PictureBox.BackgroundImage.

And, as I said, you can instead write on top of both that is onto the PBox's surface. For this use the Paint event, Invalidate to trigger it and class level variables to hold the necessary data..

The latter is for graphics that will change a lot, the two former ones are for changes that accumulate.

Control.CreateGraphics is for transient graphics only, like a rubber-band line or a cursor cross..