将html table / chart元素转换为图像

Question

This is something I have tried to do during my free time. However I'm not yet sure of the complexities and problems I might face. I would like to go to a url like this: https://fred.stlouisfed.org/series/DFII5 and save this chart as an image , anywhere locally on my pc.

My first approach was to use either the html agility pack:

 var document = new HtmlWeb().Load("https://fred.stlouisfed.org/series/DFII5");
        var urls = document.DocumentNode.Descendants("img")
                                        .Select(e => e.GetAttributeValue("src", null))
                                        .Where(s => !String.IsNullOrEmpty(s));

or even use the WinForms web browser control:

private void GetWebpage(string url)
    {
        WebBrowser browser = new WebBrowser();
        browser.Navigate(url);
        browser.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(browser_DocumentCompleted);

    }

    void browser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
    {
        var browser = (WebBrowser)sender;
        var client = new WebClient();
        foreach (var img in browser.Document.Images)
        {
            var image = img as HtmlElement;
            var src = image.GetAttribute("src").TrimEnd('/');
            if (!Uri.IsWellFormedUriString(src, UriKind.Absolute))
            {
                src = string.Concat(browser.Document.Url.AbsoluteUri, "/", src);
            }

            //Append any path to filename as needed
            var filename = new string(src.Skip(src.LastIndexOf('/') + 1).ToArray());
            File.WriteAllBytes(filename, client.DownloadData(src));
        }
    }

Both approaches have been able to fetch all the images from that webpage, however the chart is what I want, and it's not an image.

Is this task possible? Would I need libraries/nugets to do this? And how would I go about achieving this? Note: It's not necessary to do it in C#, it could be in Python or anything else.

EDIT Some further research brought these 2 to my attention: http://www.princexml.com/ and https://wkhtmltopdf.org/

They are both html to pdf libraries from what I understood. Would it be possible to use these, to get only the html of the chart and turn it to pdf?

Answer 1

Just a first idea. Yes, that graph is not an image.

So, one idea could be: Make your software do a screenshot and cut out that specific area with some image editing SDK.

For loading a website and doing a screenshot, I would think of something like Selenium. For editing the image afterwards, you could use something like ImageMagick.

Another idea could be to grab the meta data for that image from the website and draw it on your own.

Answer 2

You could try HTML2PDF converter. See https://www.html2pdf.fr

Or HTML2PS converter. See http://user.it.uu.se/%7Ejan/html2ps.html

ImageMagick can use the latter, if installed to do the conversion. See HTML section at http://www.imagemagick.org/script/formats.php