How to Convert Webpages to JPG Images in ASP.NET without Third-Party Libraries?

Converting Webpages to Images in ASP.NET without Third-Party Services

Challenge:
To fulfill the requirement of creating a function in C# that converts a webpage to a JPG image without relying on external services, it is essential to utilize the capabilities of ASP.NET.

Solution:
Leveraging a combination of techniques, the solution involves:

1. Thread-Safe Web Browser: To access the target webpage within ASP.NET, the WebBrowser control's thread-safe handling becomes vital. This aspect is addressed by combining solutions from reliable sources.
2. BMP to JPG Conversion: Once the webpage is rendered, the captured bitmap needs to be converted to JPG. A proven solution for this is incorporated into the code.

Implementation:
The provided code encompasses a new class, WebsiteToImage.cs, that effectively generates images from webpages:

public class WebsiteToImage
{
    private Bitmap m_Bitmap;
    private string m_Url;
    private string m_FileName = string.Empty;

    // Constructor with URL only
    public WebsiteToImage(string url)
    {
        m_Url = url;
    }

    // Constructor with URL and filename for saving
    public WebsiteToImage(string url, string fileName)
    {
        m_Url = url;
        m_FileName = fileName;
    }

    public Bitmap Generate()
    {
        // Start a new thread for WebBrowser operations
        var m_thread = new Thread(_Generate);
        m_thread.SetApartmentState(ApartmentState.STA);
        m_thread.Start();

        // Wait for thread to complete and retrieve the bitmap
        m_thread.Join();
        return m_Bitmap;
    }

    private void _Generate()
    {
        using (var browser = new WebBrowser { ScrollBarsEnabled = false })
        {
            // Navigate to the webpage
            browser.Navigate(m_Url);

            // Wait for the document to load
            while (browser.ReadyState != WebBrowserReadyState.Complete)
            {
                Application.DoEvents();
            }

            // Capture the webpage as a bitmap
            browser.ClientSize = new Size(browser.Document.Body.ScrollRectangle.Width, browser.Document.Body.ScrollRectangle.Bottom);
            m_Bitmap = new Bitmap(browser.Document.Body.ScrollRectangle.Width, browser.Document.Body.ScrollRectangle.Bottom);
            browser.BringToFront();
            browser.DrawToBitmap(m_Bitmap, browser.Bounds);

            // Save the bitmap to file if a filename was provided
            if (m_FileName.Length > 0)
            {
                // Save as JPG using custom bitmap extension
                m_Bitmap.SaveJPG100(m_FileName);
            }
        }
    }
}

Extension Method for Saving BMP as JPG:
The following extension method simplifies saving a bitmap as JPG with high quality:

public static void SaveJPG100(this Bitmap bmp, string filename)
{
    var encoderParameters = new EncoderParameters(1);
    encoderParameters.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L);
    bmp.Save(filename, GetEncoder(ImageFormat.Jpeg), encoderParameters);
}

Usage:
To use the WebsiteToImage class, simply create an instance and call the Generate() method to obtain a bitmap:

WebsiteToImage websiteToImage = new WebsiteToImage("https://www.example.com", @"C:\path\to\result.jpg");
Bitmap bitmap = websiteToImage.Generate();

Important Note:
To ensure this solution functions as intended, add a reference to System.Windows.Forms in your ASP.NET project.

Update:
The code has been enhanced to capture the entire webpage, eliminating the need for specific adjustments to capture only parts of the page.

The above is the detailed content of How to Convert Webpages to JPG Images in ASP.NET without Third-Party Libraries?. For more information, please follow other related articles on the PHP Chinese website!