New Post: How to draw text in WPF without WriteableBitmap constructor that takes UIElement parameter?

Thanks for the quick response. It works using this approach, then blitting with my base WriteableBitmap.

On performance, I'm seeing ~600uS to create each label and cache it in a WriteableBitmap object. For my use case of ~100K items (1 item = rectangle and label), the time to create each and cache for subsequent blitting would be >55s which is too much. Is this the most performant text approach that I should expect? Would the Silverlight UIElement conversion take about the same time? Maybe this is just my wake up call that drawing text is expensive.

As for the blitting of a cached text bitmap into the base, the performance is quite reasonable averaging 720nS per-blit; thus 72ms for my 100K case, although I plan to only conditionally add the text if determined it will be readable.

Benchmark system: Core i7 Q740, 1.73Ghz, 8GB RAM, W7 x64

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To summarize my approach for others, given the performance seen:

1. Create a WriteableBitmap for the text (created on-demand and cached for future repeated use)
   a) DrawingVisual's DrawingContext.DrawText (<FormattedText>, new Point(0,0))
   b) Use the bounds of the FormattedText object as the 'sourceRect'
   c) Convert the DrawingVisual to a RenderTargetBitmap using sourceRect from (b)
   d) Create a WriteableBitmap object dimensioned the same size as sourceRect
   

            FormattedText text = new FormattedText(displayLabel,
                new System.Globalization.CultureInfo("en-us"),
                FlowDirection.LeftToRight,
                new Typeface(new FontFamily("Arial"), FontStyles.Normal, FontWeights.Normal, new FontStretch()),
                12,
                Brushes.Black);

            DrawingVisual drawingVisual = new DrawingVisual();
            DrawingContext drawingContext = drawingVisual.RenderOpen();
            drawingContext.DrawText(text, new Point(0, 0));
            drawingContext.Close();


            Rect sourceRect = new Rect(0, 0, (int)text.Width, (int)text.Height);

            RenderTargetBitmap rtb = new RenderTargetBitmap((int)sourceRect.Width, (int)sourceRect.Height, 96, 96, PixelFormats.Pbgra32);
            rtb.Render(drawingVisual);

            LabelBitmapCache = BitmapFactory.New((int)sourceRect.Width, (int)sourceRect.Height);
            rtb.CopyPixels(new Int32Rect(0, 0, rtb.PixelWidth, rtb.PixelHeight), 
                            LabelBitmapCache.BackBuffer, 
                            LabelBitmapCache.BackBufferStride * LabelBitmapCache.PixelHeight, 
                            LabelBitmapCache.BackBufferStride);

1. Conditionally blit the text cached WriteableBitmap with my base (if determined it will be readable - not shown)

_bmp.Blit(new Rect(left, 5, i.LabelBitmapCache.PixelWidth, i.LabelBitmapCache.PixelHeight), i.LabelBitmapCache, 
                                  new Rect(0,0,i.LabelVisual.ContentBounds.Width, i.LabelVisual.ContentBounds.Height));