J-P J-P - 1 year ago 166
C# Question

Panel Drawing zoom in C#

I have a Form that contain a panel, and in this panel I draw shapes, like rectangles and circles, I need to zoom into this shapes, I saw couple options but most of them using PictureBox. Should I use Bitmap creating the panel area as a bitmap and change the zooming factor ?? would this help me also further if I want to have Panning and not draw images not into the fit in the panel size.

Here is a snapshot of my code

private void panel1_Paint(object sender, PaintEventArgs e)
Graphics g = panel1.CreateGraphics();
SolidBrush myBrush = new SolidBrush(Color.Black);
Pen p = new Pen(Color.Black);
int RecScale = 1;
foreach (CircuitData.ResistorRow resistorRow in ResistorData.Resistor)
RectangleF rec = new RectangleF((float)(resistorRow.CenterX - resistorRow.Length / 2), (float)(resistorRow.CenterY - resistorRow.Width/ 2), (float)resistorRow.Length, (float)resistorRow.Width);
float orientation = 360 - (float)resistorRow.Orientation;
PointF center = new PointF((float)resistorRow.CenterX, (float)resistorRow.CenterY);
PointF[] points = CreatePolygon(rec, center, orientation);
if (!Double.IsNaN(resistorRow.HiX) && !Double.IsNaN(resistorRow.HiY))
g.FillEllipse(myBrush, (float)resistorRow.HiX - 5 , (float)resistorRow.HiY - 5, 10, 10);
g.DrawLine(p, new PointF((float)resistorRow.HiX, (float)resistorRow.HiY), center);
g.FillPolygon(myBrush, points);

Can a sample code be provided.
Many Thanks


Answer Source

Here is a way to scale the drawing by scaling the Graphics object:

private void panel1_Paint(object sender, PaintEventArgs e)
    Graphics g = e.Graphics;
    g.ScaleTransform(zoom, zoom);

    // some demo drawing:
    Rectangle rect = panel1.ClientRectangle;
    g.DrawEllipse(Pens.Firebrick, rect);
    using (Pen pen = new Pen(Color.DarkBlue, 4f)) g.DrawLine(pen, 22, 22, 88, 88);


Here we store the zoom level:

float zoom = 1f;

Here we set it and update the Panel:

private void trackBar1_Scroll(object sender, EventArgs e)
   // let the value go from, say 1-100, initialize to 100 !
    zoom = trackBar1.Value / 100f;  

Two example screenshots:

enter image description hereenter image description here

Note how nicely this scales the Pen widths as well. Turning on antialiasing would be a good idea..: g.SmoothingMode = SmoothingMode.AntiAlias;

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