How to Create a PNG File from a Web Page in C#

Both Google Chrome and Microsoft Edge provide a feature for creating a PNG file from the currently visible viewport. For this, you start the browser executable in “headless mode”, i.e., without the UI (command line argument --headless), and provide the path of the output file (—screenshot=<path>).

Using this from C# code is straightforward:

void HtmlToPng(string source, string outputFilePath)
{
    var arguments = $"--headless --disable-gpu --default-background-color=00000000 --window-size=1920,1080 --hide-scrollbars --screenshot=\"{outputFilePath}\" \"{source}\"";

    var process = new System.Diagnostics.Process();
    process.StartInfo.FileName = "msedge"; // or "chrome"
    process.StartInfo.Arguments = arguments;
    process.StartInfo.UseShellExecute = true;
    process.Start();
}

Examples:

HtmlToPng("https://www.example.com", @"C:\example\output.png");

HtmlToPng(@"C:\example\input.html", @"C:\example\output.png");

(For complete code, download the demo project on GitHub)

Details

• By starting the process with UseShellExcute = true, we do not have to care about the exact location of the Edge (or Chrome) executable – specifying msedge or chrome is sufficient.
• --disable-gpu is taken from the Google docs (we don’t need a GPU for what is basically one frame).
• --default-background-color specifies the background color to use if the page itself has no background set. The color is a hex value in the format AARRGGBB (AA = alpha). 00000000 means transparent; 0 also works, but could be confused with “black” when reading the code later.
• --window-size specifies the size of the area available for the webpage to render. The created PNG file will only show this area.
• The --hide-scrollbars takes care of scrollbars that may appear if the page needs more space than available.