CODEWITHSUNDEEP
c#wpf
Haider
Haider

Reputation: 615

image quality is blurry

I have a situation where I want to convert some XAML to an image, so I created a RichTextBox and then took the image of it. Now problem is that words in image is blurred, any idea how I might be able to fix it?

public System.Drawing.Bitmap ConvertXamltoImage(string XamlString, int Width, int Height)
{

    RichTextBox AdContentRichTextBox = new RichTextBox() { Width = Width, Height = Height };
    AdContentRichTextBox.BorderThickness = new Thickness(0);
    XmlReader _XmlReader = XmlReader.Create(new StringReader(XamlString));

    AdContentRichTextBox.Document = XamlString;          

    var size = new Size(Width, Height);
    AdContentRichTextBox.Measure(size);
    AdContentRichTextBox.Arrange(new Rect(size));
    RenderTargetBitmap bmp = new RenderTargetBitmap(Width, Height, 300, 300, PixelFormats.Pbgra32);

    bmp.Render(AdContentRichTextBox);


    DrawingVisual _drawingVisual = new DrawingVisual();

    using (DrawingContext _drwaingContext = _drawingVisual.RenderOpen())
    {
        VisualBrush _visualBrush = new VisualBrush(AdContentRichTextBox);
    }

    PngBitmapEncoder _png = new PngBitmapEncoder();

    _png.Frames.Add(BitmapFrame.Create(bmp));
    System.Drawing.Bitmap _tempBitmap = null;
    using (Stream _fileStream = new MemoryStream())
    {
        _png.Save(_fileStream);
        _tempBitmap = new System.Drawing.Bitmap(_fileStream);

        _fileStream.Flush();
    }
    return _tempBitmap;
}

Upvotes: 0

Views: 3015

Answers (1)

Colin Smith
Colin Smith

Reputation: 12540

Hmmmm..there could be lots of things all interacting here:

1st

"Grayscale fall back - if ClearType is disabled or one is rendering text in certain situations where the ClearType algorithm cannot be run, WPF will use a grayscale rendering algorithm to antialias the rendered text."

Rendering Text to a RenderTargetBitmap seems to be one of those situations....(the renderer switches from a hardware to a software path).

2nd

In addition NET 4 switched the default scaling algorithm from high-quality (Fant) to low-quality (Bi-Linear).....now that shouldn't come into play here as it doesn't look like you are scaling the bitmap in any way...but you never know what's going on inside. It's possible to switch the scaler back to the higher quality one.

3rd

You may need to take into account the parent container of the RichTextBox...see last link below, mentions it can distort the font rendering.

Some ideas on how to work around this are:

  1. render the RichTextBox at a higher resolution e.g. 600dpi, and then scale down the bitmap (probably will make no difference)

  2. capture the screen....difficult or not practical if your visual is offscreen/obscured, etc.

See related links:

Upvotes: 4

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