How can i color the pixels that are only in the area of the rectangle i'm drawing on the picturebox1 ?

Question

In the form i have picturebox mouse down event:
bool DrawIt = false;
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
timer1.Stop();
LoadPictureAt(trackBar1.Value, sender);
pictureBox1.Refresh();
if (e.Button == MouseButtons.Left)
rect = new Rectangle(e.X, e.Y, 0, 0);
DrawIt = true;
pictureBox1.Refresh();
rect is a global Rectangle variable.
The the picturebox mouse move event:
List<Point> NewPoints = new List<Point>();
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
if (e.Button == System.Windows.Forms.MouseButtons.Left)
if (DrawIt == true)
rect = new Rectangle(rect.Left, rect.Top, Math.Min(e.X - rect.Left, pictureBox1.ClientRectangle.Width - rect.Left), Math.Min(e.Y - rect.Top, pictureBox1.ClientRectangle.Height - rect.Top));
NewPoints.Add(e.Location);
pictureBox1.Refresh();
In the mouse move event i'm drawing the rectangle i didn't check it yet but in the move event i want to draw the rectangle in real time on the picturebox1.
Then the paint event:
private void pictureBox1_Paint(object sender, PaintEventArgs e)
if (cloudPoints != null)
if (DrawIt)
CloudEnteringAlert.pointtocolorinrectangle = cloudPoints;
Bitmap bmp = new Bitmap(pictureBox1.Width, pictureBox1.Height, PixelFormat.Format32bppArgb);
CloudEnteringAlert.Paint(e.Graphics, 1, 200, bmp);
First in the paint event how do i use the rect to draw the rectangle ?
Second cloudPoints contain all the pixels in the pictureBox1 Image. Could be 44000 or 400.
cloudPoints is a List<Point>  For example in cloudPoints index 0 i have a coordinate x = 100 y = 200 of a pixel.
Then i send the pixels coordinates to another class with Paint method and color the pixels in yellow.
But instead sending all the pixels coordinates in ccloudPoints i want to send to the paint event only the pixels coordinates from cloudPoints that exist inside the rectangle i was drawing. Only the pixels in the rectangle i was drawing.
So in the end the List<Point> pointtocolorinrectangle will contain only the pixels coordinates exist in the rectangle i was drawing.
1. How to fix the code in the move event ?
2. How to change the code in the paint event so it will send coordinates of pixels only that exist in the drawn rectangle.

Answer 1

I did it this way:
bool DrawIt = false;
private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
timer1.Stop();
LoadPictureAt(trackBar1.Value, sender);
pictureBox1.Refresh();
if (e.Button == MouseButtons.Left)
rect = new Rectangle(e.X, e.Y, 0, 0);
DrawIt = true;
pictureBox1.Refresh();
List<Point> NewPoints = new List<Point>();
private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
if (e.Button == System.Windows.Forms.MouseButtons.Left)
if (DrawIt == true)
rect = new Rectangle(rect.Left, rect.Top, Math.Min(e.X - rect.Left, pictureBox1.ClientRectangle.Width - rect.Left), Math.Min(e.Y - rect.Top, pictureBox1.ClientRectangle.Height - rect.Top));
NewPoints.Add(e.Location);
pictureBox1.Refresh();
private void pictureBox1_Paint(object sender, PaintEventArgs e)
if (cloudPoints != null)
if (DrawIt)
e.Graphics.DrawRectangle(pen, rect);
var pointsAffected = cloudPoints.Where(pt => rect.Contains(pt));
CloudEnteringAlert.pointtocolorinrectangle = pointsAffected.ToList();
Bitmap bmp = new Bitmap(pictureBox1.Width, pictureBox1.Height, PixelFormat.Format32bppArgb);
CloudEnteringAlert.Paint(e.Graphics, 1, 200, bmp);
Working perfect just what i needed.