Question

I use a Gecko .NET WebBrowser control to get the HTML page.

Then I use this code to make a screenshot of this HTML page:

void LoadingFinished(object sender, EventArgs args)
{
    try
    {
        myBrowser.Document.Body.SetAttribute("style", "overflow:hidden");
        if (screenshotkey != "")
        {
            Bitmap bitmap = new Bitmap(myBrowser.Width, myBrowser.Height);
            myBrowser.DrawToBitmap(bitmap, new Rectangle(0, 0, myBrowser.Width, myBrowser.Height));
            bitmap.Save("Screenshots/" + screenshotkey + ".png", ImageFormat.Png);
        }
    }
    catch (Exception dfkvsn)
    {
        errorloadingpage();
    }
}

I removed some stuff from the code above that is not very important – like setting browser width, etc. Originally the code is 100% functional.

The problem is that when it saves a png screenshot (DrawToBitmap line) – at some places the created picture has the white pixels that should not be there (WebBrowser originally does not have them), see the link.

Same thing was happening when I was using standard .NET WebBrowser control, so it’s not Gecko problem.

I have no idea how to approach this.
Is there a better way to save it to bitmap? Or is this the best .NET can do?

Answer 1

Fixed it.
It turned out that pixels that seemed to be white – were just transparent.
And they were only in places where picture had a deepest black color (RGB 0, 0, 0)
For some reason .NET couldn’t save this color to the file.
So I simply added the line of code that makes entire picture black, and on top of that I record my screenshot.
Since it’s 2 layers now – transparent pixels now seem to be black – just what I wanted – no white pixels.
Here’s the final code:

void LoadingFinished(object sender, EventArgs args)
        {
            try
            {
                myBrowser.Document.Body.SetAttribute("style", "overflow:hidden");
                if (screenshotkey != "")
                {
                    panel1.Height = myBrowser.Document.Body.ScrollHeight;
                    panel1.Width = myBrowser.Document.Body.ScrollWidth;
                    this.Size = new System.Drawing.Size(panel1.Width+20, panel1.Height+20);

                    if (!Directory.Exists("Screenshots"))
                    {
                        Directory.CreateDirectory("Screenshots");
                    }

                    Bitmap bitmap = new Bitmap(myBrowser.Width, myBrowser.Height);
                    for (int Xcount = 0; Xcount < bitmap.Width; Xcount++)
                    {
                        for (int Ycount = 0; Ycount < bitmap.Height; Ycount++)
                        {

                            bitmap.SetPixel(Xcount, Ycount, Color.Black);
                        }
                    }
                    myBrowser.DrawToBitmap(bitmap, new Rectangle(0, 0, myBrowser.Width, myBrowser.Height));
                    bitmap.Save("Screenshots/" + screenshotkey + ".png", ImageFormat.Png);
                }
            }
            catch (Exception dfkvsn)
            {
                errorloadingpage();
            }
        }