Full page screenshot with webdriver

fullpagescreenshot.cs

public Image GetEntireScreenshot()
{
    // Get the total size of the page
    var totalWidth = (int) (long) ((IJavaScriptExecutor) driver).ExecuteScript("return document.body.offsetWidth"); //documentElement.scrollWidth");
    var totalHeight = (int) (long) ((IJavaScriptExecutor) driver).ExecuteScript("return  document.body.parentNode.scrollHeight");
    // Get the size of the viewport
    var viewportWidth = (int) (long) ((IJavaScriptExecutor) driver).ExecuteScript("return document.body.clientWidth"); //documentElement.scrollWidth");
    var viewportHeight = (int) (long) ((IJavaScriptExecutor) driver).ExecuteScript("return window.innerHeight"); //documentElement.scrollWidth");

    // We only care about taking multiple images together if it doesn't already fit
    if (totalWidth <= viewportWidth && totalHeight <= viewportHeight)
    {
        var screenshot = driver.TakeScreenshot();
        return ScreenshotToImage(screenshot);
    }
    // Split the screen in multiple Rectangles
    var rectangles = new List<Rectangle>();
    // Loop until the totalHeight is reached
    for (var y = 0; y < totalHeight; y += viewportHeight)
    {
        var newHeight = viewportHeight;
        // Fix if the height of the element is too big
        if (y + viewportHeight > totalHeight)
        {
            newHeight = totalHeight - y;
        }
        // Loop until the totalWidth is reached
        for (var x = 0; x < totalWidth; x += viewportWidth)
        {
            var newWidth = viewportWidth;
            // Fix if the Width of the Element is too big
            if (x + viewportWidth > totalWidth)
            {
                newWidth = totalWidth - x;
            }
            // Create and add the Rectangle
            var currRect = new Rectangle(x, y, newWidth, newHeight);
            rectangles.Add(currRect);
        }
    }
    // Build the Image
    var stitchedImage = new Bitmap(totalWidth, totalHeight);
    // Get all Screenshots and stitch them together
    var previous = Rectangle.Empty;
    foreach (var rectangle in rectangles)
    {
        // Calculate the scrolling (if needed)
        if (previous != Rectangle.Empty)
        {
            var xDiff = rectangle.Right - previous.Right;
            var yDiff = rectangle.Bottom - previous.Bottom;
            // Scroll
            ((IJavaScriptExecutor) driver).ExecuteScript(String.Format("window.scrollBy({0}, {1})", xDiff, yDiff));
        }
        // Take Screenshot
        var screenshot = driver.TakeScreenshot();
        // Build an Image out of the Screenshot
        var screenshotImage = ScreenshotToImage(screenshot);
        // Calculate the source Rectangle
        var sourceRectangle = new Rectangle(viewportWidth - rectangle.Width, viewportHeight - rectangle.Height, rectangle.Width, rectangle.Height);
        // Copy the Image
        using (var graphics = Graphics.FromImage(stitchedImage))
        {
            graphics.DrawImage(screenshotImage, rectangle, sourceRectangle, GraphicsUnit.Pixel);
        }
        // Set the Previous Rectangle
        previous = rectangle;
    }
    return stitchedImage;
}

private static Image ScreenshotToImage(Screenshot screenshot)
{
    Image screenshotImage;
    using (var memStream = new MemoryStream(screenshot.AsByteArray))
    {
        screenshotImage = Image.FromStream(memStream);
    }
    return screenshotImage;
}