How to render any HTML tags and CSS attributes in reports

RELATED TO:

AUTHOR: Ekaterina Martynyuk

DATE POSTED: June 06, 2017

Article information

Article relates to

Telerik Reporting

Created by

Katia, Telerik

Last modified

June 6th, 2017

Last modified by

Katia, Telerik

PROBLEM

A frequently asked question is how to render HTML tags and CSS attributes that are not supported by HtmlTextBox item in reports.

SOLUTION

The approach includes utilizing a WebBrowser control to render HTML to a bitmap with a help of a user defined function and a PictureBox item that will display the generated image (PNG):
static public Image HTML2BitMap(string url, Telerik.Reporting.Processing.PictureBox me)
        {
            Hashtable data = new Hashtable();
            data["url"] = url;
            data["image"] = null;
            // We expect PictureBox dimesions in pixels
            data["w"] = (int)me.Width.Value;
            data["h"] = (int)me.Height.Value;
            Thread t = new Thread(new ParameterizedThreadStart(Report1.GetImage));
            t.TrySetApartmentState(ApartmentState.STA);
            t.Start(data);
            t.Join();
            if (t.IsAlive)
                t.Abort();
 
            MemoryStream ms = new MemoryStream((byte[])data["image"]);
            Image img = Image.FromStream(ms);
            //Resize the PictureBox to the actual size of the browser image
            //me.Height = new Unit(img.Height,UnitType.Pixel);
            //me.Width = new Unit(img.Width, UnitType.Pixel);
            return img;
        }
 
        static public void GetImage(object _data)
        {
            Hashtable data = (Hashtable)_data;
            using (WebBrowser browser = new WebBrowser())
            {
                browser.ScrollBarsEnabled = false;
                // Set browser prefered size
                browser.Size = new Size((int)data["w"], (int)data["h"]);
 
                browser.DocumentText = (string)data["url"];
                while (browser.ReadyState != WebBrowserReadyState.Complete)
                    Application.DoEvents();
 
                Size sz = browser.Document.Body.ScrollRectangle.Size;
 
                using (Bitmap myBitmap = new Bitmap(sz.Width, sz.Height))
                {
                    browser.ClientSize = sz;
 
                    Rectangle drawRectangle = new Rectangle(0, 0, sz.Width, sz.Height);
                    browser.DrawToBitmap(myBitmap, drawRectangle);
 
                    MemoryStream ms = new MemoryStream();
                    myBitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
 
                    data["image"] = ms.ToArray();
                }
            }
        }

Note: this approach has several shortcomings and is far from perfect, but it seems to work in most cases and in all export formats (because all support the PictureBox item).

The attached project demonstrates the described approach. One thing to note is that you should set the HTML as a value for the browser.DocumentText property, in the attached example we used URL from the RadEditor examples to quickly illustrate the approach.

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