How to draw lines in c#

Question

i have a school project where i have to have a function that can draw a line from anywhere on the screen to anywhere else on the screen. i know that there are some functions included that do it for me.

this is what i have so far: (the vga.setpixel thing sets the (uint)x pixel, at the (uint)y pixal, the color (uint) color)

class drawaline
{
   public static void swap(ref int a, ref int b)
{
    int temp = a; // Copy the first position's element
    a = b; // Assign to the second element
    b = temp; // Assign to the first element
}
public static int abs(int value)
{
    if (value < 0)
        value = value * -1;
    return value;
}
public static int fpart(int x)
{
    return x;
}
public static int rfpart(int x)
{
    x = 1 - fpart(x);
    return x;
}
public static int ipart(int x)
{
    return x;
}
public static void line(int x1, int y1, int x2, int y2, uint color)
{
    int dx = x2 - x1;
    int dy = y2 - y1;
    if (abs(dx) < (dy))
    {
        swap(ref x1, ref y1);
        swap(ref x2, ref y2);
        swap(ref dx, ref dy);
    }
    if (x2 < x1)
    {
        swap(ref x1, ref x2);
        swap(ref y1, ref y2);
    }
    int gradient = dy / dx;
    // handle first endpoint
    int xend = x1;
    int yend = y1 + gradient * (xend - x1);
    int x1p = x1 + (int).5;
    int xgap = rfpart(x1p);
    int xpxl1 = xend; // this will be used in the main loop
    int ypxl1 = ipart(yend);
    VGAScreen.SetPixel320x200x8((uint)xpxl1, (uint)ypxl1, (uint)color);
    int intery = yend + gradient; // first y-intersection for the main loop
    // handle second endpoint
    xend = x2;
    yend = y2 + gradient * (xend - x2);
    xgap = fpart(x2 + (int)0.5);
    int xpxl2 = xend; // this will be used in the main loop
    int ypxl2 = ipart(yend);
    VGAScreen.SetPixel320x200x8((uint)xpxl2, (uint)ypxl2, (uint)color);
    VGAScreen.SetPixel320x200x8((uint)xpxl2, (uint)ypxl2 + 1, (uint)color);

    // main loop
    for (x = 0; x < xpxl1 + 1; x++)
    {
        VGAScreen.SetPixel320x200x8((uint)x, (uint)intery, (uint)color);
        VGAScreen.SetPixel320x200x8((uint)x, (uint)intery, (uint)color);
        intery = intery + gradient;
    }
}
}

Answer 1

Many mistakes:

1. swap needs to take its parameters as ref
2. There is Math.Abs which you can use instead of writing your own(Technically not a mistake but bad style)
3. Your fpart function most likely doesn't do what you want it to do. I assume it should return the fractional part of a double and not the int passed in. Make it take and return a double.
4. (int)0.5 doesn't make sense. It becomes 0.
5. Most of your int variables should be double instead. Since your code assumes that they can contain non integral numbers.
6. int gradient = dy / dx uses integer division. You need to cast one of them to double before dividing or you lose the fractional part.

Answer 2

void draw_line()
        {
            Pen mypen;
            mypen = new Pen(Color.Black , 1);
            Graphics g = this.CreateGraphics();
            g.DrawLine(mypen, 0, 20, 1000, 20); 
            // 0,20 are starting points and 1000,20 are destination.
            mypen.Dispose();
            g.Dispose();
        }

Answer 3

Check this it will help you

there is an icon.cs file which contains the code you want

Answer 4

Graphics g = this.CreateGraphics ();
Pen p = new Pen (Color.Black , 8);

//draw line method 1
//in this method we are declaring two different points 
//The First one is x and y coordinates 

PointF p1 = new PointF(0.0F, 0.0F);

//The second one is starting and ending points
PointF p2 = new PointF(200.0F, 0.0F);
        
//this is used for drawling line
e.Graphics.DrawLine(p, p1, p2);

//The second Method is simplest one 

e.Graphics.DrawLine (p,100,150,40,40);