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convert html string to an image dynamically (continue2)

Posted on 2009-05-13
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Last Modified: 2012-05-06
I want to use following code (see also related question)  to creata dynamically an image from html.
How do I change it so that it works for web application (C#)?


[STAThread()]  << -- attribute
protected void Page_Load(object sender, EventArgs e)
{
 System.Windows.Forms.WebBrowser wb = new System.Windows.Forms.WebBrowser();
      wb.Size = new System.Drawing.Size(1024, 768);
      wb.ScrollBarsEnabled = false;
 
      wb.DocumentCompleted += new System.Windows.Forms.WebBrowserDocumentCompletedEventHandler(delegate(object sender, System.Windows.Forms.WebBrowserDocumentCompletedEventArgs e) {
        System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(wb.ClientRectangle.Width, wb.ClientRectangle.Height);
        wb.DrawToBitmap(bmp, new System.Drawing.Rectangle(0,0, bmp.Width, bmp.Height));
        bmp.Save(@"c:\foo.bmp", System.Drawing.Imaging.ImageFormat.Bmp);
      });
      wb.Navigate(@"file://c:\my.html");
      //wb.Navigate("http://www.google.com"); 
 
}

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Question by:johnkainn
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8 Comments
 
LVL 15

Expert Comment

by:oobayly
ID: 24380430
What do you mean by "so that it works"? Are you wanting to use the page to save the image on the webserver, or return the resulting image to the client?

If it's the latter, you could modify the code to write the bitmap to a member variable. Then poll the result until it's valid & write it to the response.

I'd suggest saving local copies of the image, and check for them first. That way you don't have to recreate the image each time.
private Bitmap bmp;
 
[STAThread()]  << -- attribute
protected void Page_Load(object sender, EventArgs e) {
  System.Windows.Forms.WebBrowser wb = new System.Windows.Forms.WebBrowser(); 
  wb.Size = new System.Drawing.Size(1024, 768);
  wb.ScrollBarsEnabled = false;
 
  wb.DocumentCompleted += new System.Windows.Forms.WebBrowserDocumentCompletedEventHandler(delegate(object sender, System.Windows.Forms.WebBrowserDocumentCompletedEventArgs e) {
    bmp = new System.Drawing.Bitmap(wb.ClientRectangle.Width, wb.ClientRectangle.Height);
    wb.DocumentCompleted += new System.Windows.Forms.WebBrowserDocumentCompletedEventHandler(delegate(object sender, System.Windows.Forms.WebBrowserDocumentCompletedEventArgs e) {
      System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(wb.ClientRectangle.Width,  wb.ClientRectangle.Height);
      wb.DrawToBitmap(bmp, new System.Drawing.Rectangle(0,0, bmp.Width, bmp.Height));
  });
  wb.Navigate(@"file://c:\my.html");
 
  // Wait for the download to complete 
  while (bmp == null){
    Thread.Sleep(50);
  }
  
  // Write to a PNG (stream needs to be seekable)
  MemoryStream ms = new MemoryStream();
  bmp.Save(ms, ImageFormat.Png);
  
  // Send the image to the client
  Response.ContentType = "image/png";
  ms.WriteTo(Response.OutputStream);
  
  ms.Dispose();
  bmp.Dispose();
}

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Author Comment

by:johnkainn
ID: 24383145
I want to save the image to a webserver.
I get an error using System.Windows.Forms.WebBrowser
( The type or namespace name 'Windows' does not exist in the namespace 'System' (are you missing an assembly reference?)  )
How should I write it so it works for web application?
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LVL 23

Expert Comment

by:Tony McCreath
ID: 24384649
I've been trying to get this to work.

The STAThread attribute didn't work for me so I added AspCompat="true" to the Page....

<%@ Page ... AspCompat="true"  %>

And you need to add a reference the System.Windows.Forms

At the moment I can't get the Navigate(url) to trigger anything. I've added event handers to DocumentCompleted, ProgressChanged and StatusTextChanged. non of them fire.

oobayly, your version of the code has nested DocumentCompleted events, is this correct?


		System.Windows.Forms.WebBrowser wb = new System.Windows.Forms.WebBrowser();
		wb.Size = new System.Drawing.Size(1024, 768);
		wb.ScrollBarsEnabled = false;
 
		wb.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(this.DocumentCompleted);
 
		wb.ProgressChanged += new WebBrowserProgressChangedEventHandler(wb_ProgressChanged);
 
		wb.StatusTextChanged += new EventHandler(wb_StatusTextChanged);
 
		wb.Navigate(url);
 
		// Wait for the download to complete 
		while (this.bmp == null)
			Thread.Sleep(50);
 
 
		// Write to a JPG (stream needs to be seekable)
		MemoryStream ms = new MemoryStream();
		bmp.Save(ms, ImageFormat.Jpeg);
 
		// Send the image to the client
		this.Response.ContentType = "image/jpg";
		ms.WriteTo(this.Response.OutputStream);
 
		ms.Dispose();
		bmp.Dispose();

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Assisted Solution

by:oobayly
oobayly earned 200 total points
ID: 24386480
@Tiggerito
Nope, that was a mistake. Didn't have VS on the machine, so used Notepad2, and didn't catch that.

I've had a browse through my code & found this class. It doesn't seem to work with some sites though, but it is a start.
using System.Drawing;
using System.Threading;
using System.Windows.Forms;
using System.ComponentModel;
 
public class WebScreenshot {
  private Bitmap bmp;
  private Size size;
 
  [DefaultValue(typeof(Size), "1024,768")]
  public Size Size {
    get { return size; }
    set { size = value; }
  }
  
  public Bitmap GetScreenshot(string uri) {
    return GetScreenshot(new Uri(uri));
  }
 
  public Bitmap GetScreenshot(Uri uri) {
    /* Start the GetScreenshot method in a single-apartment thread
     * Pass the Uri as the parameter
     * Wait for the thread to join to make the method act synchronously
     */
    Thread td = new Thread(new ParameterizedThreadStart(GetScreenshot));
    td.SetApartmentState(ApartmentState.STA);
    td.Start(uri);
    td.Join();
 
    return bmp;
  }
 
  private void GetScreenshot(object uri) {
    // Create the browser object using the desired size
    WebBrowser wb = new WebBrowser();
    wb.Size = size;
    wb.ScrollBarsEnabled = false;
 
    // Navigate to the Uri & wait for it to finish downloading
    wb.Navigate(uri as Uri);
    while (wb.ReadyState != WebBrowserReadyState.Complete) {
      System.Windows.Forms.Application.DoEvents();
    }
 
    // Draw the rendered html to the bitmap
    bmp = new System.Drawing.Bitmap(wb.ClientRectangle.Width, wb.ClientRectangle.Height);
    wb.DrawToBitmap(bmp, new Rectangle(0, 0, bmp.Width, bmp.Height));
  }
 
  public WebScreenshot() : this(new Size(1024, 768)) { }
 
  public WebScreenshot(int width, int height) : this(new Size(width, height)) { }
  
  public WebScreenshot(Size size) {
    this.size = size;
  }
}

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Author Comment

by:johnkainn
ID: 24394855
Thanks. Unfortunately I am getting errors when I try to run this code.

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LVL 23

Expert Comment

by:Tony McCreath
ID: 24395173
johnkainn,

could you explain what the errors are!
0
 

Author Comment

by:johnkainn
ID: 24405765
I get following errors:
1)  Error    18    The type or namespace name 'Windows' does not exist in the namespace 'System' (are you missing an assembly reference?)

2) Error    17    The name 'WebBrowserReadyState' does not exist in the current context    

3) Error    16    The type or namespace name 'Uri' could not be found (are you missing a using directive or an assembly reference?)    

4) Error    15    The type or namespace name 'WebBrowser' could not be found (are you missing a using directive or an assembly reference?)    






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LVL 23

Accepted Solution

by:
Tony McCreath earned 300 total points
ID: 24405913
Th first error is that you havent included a reference to the System.Windows.Forms dll.

Add a reference to it. You should see menu options at the project level.
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