Convert HTML to JPEG, PNG or BMP Images in ASP.NET Applications with C# and VB.NET

Winnovative HTML to Image Converter can be used in any type of .NET application to convert HTML pages to raster images and to create thumbnails of the HTML pages. The HTML to Image Converter is not a standalone product, it is part of the HTML to PDF Converter Library for .NET and is represented by the HtmlToImageConverter class of that library. Using this class you can convert HTML pages to any type of raster image supported by the .NET framework like BMP, JPEG, PNG or GIF. When converting to PNG you can also choose to produce an image with transparent background.

The code below was taken from the HTML to Image Converter demo application available for download in the HTML to PDF Converter product package. In this sample an instance of the HtmlToImageConverter class is constructed and used to rasterize the HTML page to an image.

protected void convertToImageButton_Click(object sender, EventArgs e)
{
    // Create a HTML to Image converter object with default settings
    HtmlToImageConverter htmlToImageConverter = new HtmlToImageConverter();

    // Set HTML Viewer width in pixels which is the equivalent in converter of the browser window width
    htmlToImageConverter.HtmlViewerWidth = int.Parse(htmlViewerWidthTextBox.Text);

    // Set HTML viewer height in pixels to convert the top part of a HTML page 
    // Leave it not set to convert the entire HTML
    if (htmlViewerHeightTextBox.Text.Length > 0)
        htmlToImageConverter.HtmlViewerHeight = int.Parse(htmlViewerHeightTextBox.Text);

    // Set if the created image has a transparent background
    htmlToImageConverter.TransparentBackground = SelectedImageFormat() == System.Drawing.Imaging.ImageFormat.Png ? transparentBackgroundCheckBox.Checked : false;

    // Set the maximum time in seconds to wait for HTML page to be loaded 
    // Leave it not set for a default 60 seconds maximum wait time
    htmlToImageConverter.NavigationTimeout = int.Parse(navigationTimeoutTextBox.Text);

    // Set an adddional delay in seconds to wait for JavaScript or AJAX calls after page load completed
    // Set this property to 0 if you don't need to wait for such asynchcronous operations to finish
    if (conversionDelayTextBox.Text.Length > 0)
        htmlToImageConverter.ConversionDelay = int.Parse(conversionDelayTextBox.Text);

    System.Drawing.Image[] imageTiles = null;

    if (convertUrlRadioButton.Checked)
    {
        string url = urlTextBox.Text;

        // Convert the HTML page given by an URL to a set of Image objects
        imageTiles = htmlToImageConverter.ConvertUrlToImageTiles(url);
    }
    else
    {
        string htmlString = htmlStringTextBox.Text;
        string baseUrl = baseUrlTextBox.Text;

        // Convert a HTML string with a base URL to a set of Image objects
        imageTiles = htmlToImageConverter.ConvertHtmlToImageTiles(htmlString, baseUrl);
    }

    // Save the first image tile to a memory buffer

    System.Drawing.Image outImage = imageTiles[0];

    // Create a memory stream where to save the image
    System.IO.MemoryStream imageOutputStream = new System.IO.MemoryStream();

    // Save the image to memory stream
    outImage.Save(imageOutputStream, SelectedImageFormat());

    // Write the memory stream to a memory buffer
    imageOutputStream.Position = 0;
    byte[] outImageBuffer = imageOutputStream.ToArray();

    // Close the output memory stream
    imageOutputStream.Close();

    // Send the image as response to browser

    string imageFormatName = imageFormatComboBox.SelectedValue.ToLower();

    // Set response content type
    Response.AddHeader("Content-Type", "image/" + (imageFormatName == "jpg" ? "jpeg" : imageFormatName));

    // Instruct the browser to open the image file as an attachment or inline
    Response.AddHeader("Content-Disposition", String.Format("attachment; filename={0}; size={1}", "HTML_to_Image." + imageFormatName, outImageBuffer.Length.ToString()));

    // Write the image buffer to HTTP response
    Response.BinaryWrite(outImageBuffer);

    // End the HTTP response and stop the current page processing
    Response.End();
}

 

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