How do I draw a line using system.drawing

Question

1.00/5 (1 vote)

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I have written this program with "using System.Drawing;":

I do not know if it worked because there is no yellow just a blank webpage.

Is there something I need to put in Default.aspx so this will work?

C#

Bitmap xPanel = new Bitmap(200, 200);
Graphics objGraphicPanel = Graphics.FromImage(xPanel);
//Background White
SolidBrush yellowBrush = new SolidBrush(Color.Yellow);
objGraphicPanel.FillRectangle(yellowBrush, 0, 0, 200, 200);

//Text
SolidBrush blackBrush = new SolidBrush(Color.Black);
Font horzFont = new Font("Verdana", 10, FontStyle.Regular);
objGraphicPanel.DrawString("Test", horzFont, blackBrush, 15, 80);

//Line
Pen colorPen = new Pen(Color.Green, 2);
objGraphicPanel.DrawLine(colorPen, 10, 100, 120, 190);

xPanel.Save("c:\path\graphicline.png");
objGraphicPanel.Dispose();
xPanel.Dispose();

What I have tried:

xPanel.Save(Server.MapPath("graphicline.png"), System.Drawing.Imaging.ImageFormat.Png);

Posted 3-Jun-16 19:48pm

Member 11242200

Updated 3-Jun-16 20:16pm

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OriginalGriff · Accepted Answer · 2016-06-03T20:16:00

The only change I needed to make to your code was to add an atsign:

C#

xPanel.Save(@"c:\path\graphicline.png");

Without it your code would not compile. Changing that to a valid folder on my PC, I can then look at the file it generated: Dropbox - graphicline.png[^] As you can see, it's yellow, has the word "Text" and a green diagonal line.
But...that won't display on a webpage. Not unless you specifically tell the page to display it, which you don't!
Instead of saving the image to a file and disposing of the bitmap - which isn't a good idea in a website, as multiple users may want different pictures - You need to display the bitmap directly.
There are a lot of ways to do that, but the simplest is to add an Image control to your page and give it the bytes that make up the image:

ASP.NET

<img ID="MyImage" runat="server" />

C#

using (Bitmap xPanel = new Bitmap(200, 200))
    {
    using (Graphics objGraphicPanel = Graphics.FromImage(xPanel))
        {
        //Background White
        SolidBrush yellowBrush = new SolidBrush(Color.Yellow);
        objGraphicPanel.FillRectangle(yellowBrush, 0, 0, 200, 200);
        //Text
        SolidBrush blackBrush = new SolidBrush(Color.Black);
        Font horzFont = new Font("Verdana", 10, FontStyle.Regular);
        objGraphicPanel.DrawString("Test", horzFont, blackBrush, 15, 80);
        //Line
        Pen colorPen = new Pen(Color.Green, 2);
        objGraphicPanel.DrawLine(colorPen, 10, 100, 120, 190);
        MemoryStream ms = new MemoryStream();
        xPanel.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
        string base64 = Convert.ToBase64String(ms.ToArray());
        MyImage.Src = "data:image/gif;base64," + base64;
        }
    }