Zooming in on quadratic curve line in c#

问题

I am relatively new to c# and i am trying to draw the quadratic curve with an X and Y graph to scale with. The i drew curve although appears at the upper left corner of the screen which is very small and barely noticeable. Is there possible way to enlarge my curve line and align it to the middle so it can be shown properly?

protected override void OnPaint(PaintEventArgs e)
    {


        float a = 1, b = -3, c = -4;
        double x1, x2, x3, y1, y2, y3, delta;
        delta = (b * b) - (4 * a * c);
        x1 = ((b * (-1)) + Math.Sqrt(delta)) / (2 * a);
        y1 = a * (x1 * x1) + b * (x1) + c;
        x2 = x1 + 1;
        y2 = a * (x2 * x2) + b * (x2) + c;
        x3 = x1 - 3;
        y3 = a * (x3 * x3) + b * (x3) + c;
        int cx1 = Convert.ToInt32(x1);
        int cx2 = Convert.ToInt32(x2);
        int cx3 = Convert.ToInt32(x3);
        int cy1 = Convert.ToInt32(y1);
        int cy2 = Convert.ToInt32(y2);
        int cy3 = Convert.ToInt32(y3);

        Graphics g = e.Graphics;


        Pen aPen = new Pen(Color.Blue, 1);
        Point point1 = new Point(cx1, cy1);
        Point point2 = new Point(cx2, cy2);
        Point point3 = new Point(cx3, cy3);
        Point[] Points = { point1, point2, point3 };
        g.DrawCurve(aPen, Points);

回答1:

Yes it is possible and even rather simple to both move (Translate) and enlarge (Scale) the Graphics results by using Graphics.TranslateTransform and Matrix and Graphics.MultiplyTransform:

using System.Drawing.Drawing2D;
//..

int deltaX = 100;
int deltaY = 100;
g.TranslateTransform(deltaX, deltaY);

float factor = 2.5f;
Matrix m = new Matrix();
m.Scale(factor, factor);

g.MultiplyTransform(m);

Note that the scaling works like a lens and will enlarge the pixels. So you may want to scale down the Pen.Width when you scale up the Graphics..

Using one before..

    g.DrawEllipse(Pens.Blue, 11, 11, 55, 55);

..and two after the transformations..

    g.DrawEllipse(Pens.Red, 11, 11, 55, 55);
    using (Pen pen = new Pen(Color.Green, 1/factor))
        g.DrawEllipse(pen, 11, 11, 44, 44);

..these calls result in this image:

(I have changed the green circle's radius to avoid complete overlaying..)

It will be up to you to find the desired numbers for the moving and scaling; this will probably involve finding the minimum and maximum values for points involved..

回答2:

I would suggest that you look into Microsoft Chart controls, it has a lots of interesting features regarding how to do this kind of curves with the ability to parameterize them.

A link to a more recent version of it: here

来源：https://stackoverflow.com/questions/28445773/zooming-in-on-quadratic-curve-line-in-c-sharp

标签

zooming

bezier