How do I write text on WriteableBitmap?

Question

Right now I'm coding a game and I need to draw text onto a WriteableBitmap; how do I do this without converting from WritableBitmap to Bitmap to WriteableBitmap? I've searched for solutions already, but all of them slow down my game or need something like Silverlight to work.

something like this:

public class ResourceCounter : UIElement
{

    public ResourceCounter()
    {
        RenderBounds = new Bound(new Point(0, 0),
                                 new Point(600, 30));
    }

    private string goldAmt;
    private string woodAmt;
    private string stoneAmt;

    public override void Tick()
    {
        goldAmt = GlobalResources.Gold.ToString();
        woodAmt = GlobalResources.Wood.ToString();
        stoneAmt = GlobalResources.Stone.ToString();
    }

    public override void Draw(WriteableBitmap bitmap)
    {
        bitmap.FillRectangle(RenderBounds.A.X,
        Renderbounds.A.Y,
        Renderbounds.B.X,
        Renderbounds.B.Y,
        Colors.DarkSlateGray);
        bitmap.DrawString("text", other parameters...");
    }

}

score 1 · Accepted Answer · edited Feb 02 '20 at 09:55

1

You can share the Pixel buffer between a Bitmap and a BitmapSource

var writeableBm1 = new WriteableBitmap(200, 100, 96, 96, 
    System.Windows.Media.PixelFormats.Bgr24, null);

var w = writeableBm1.PixelWidth;
var h = writeableBm1.PixelHeight;
var stride = writeableBm1.BackBufferStride;
var pixelPtr = writeableBm1.BackBuffer;

// this is fast, changes to one object pixels will now be mirrored to the other 
var bm2 = new System.Drawing.Bitmap(
    w, h, stride, System.Drawing.Imaging.PixelFormat.Format24bppRgb, pixelPtr);

writeableBm1.Lock();

// you might wanna use this in combination with Lock / Unlock, AddDirtyRect, Freeze
// before you write to the shared Ptr
using (var g = System.Drawing.Graphics.FromImage(bm2))
{
    g.DrawString("MyText", new Font("Tahoma", 14), System.Drawing.Brushes.White, 0, 0);
}

writeableBm1.AddDirtyRect(new Int32Rect(0, 0, 200, 100));
writeableBm1.Unlock();

edited Feb 02 '20 at 09:55

Clemens

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answered Feb 02 '20 at 08:39

Charles

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Funnily enough, `PixelFormats.Bgr24` matches `Format24bppRgb`, while there is also `PixelFormats.Rgb24`. – Clemens Feb 02 '20 at 09:58
Huh, that's weird. I'll keep that in mind. Speaking of pixel formats, do you know what format BitmapFactory.New(x, y) creates? I got text to show up, but it looks stretched vertically and with very bad coloring. Edit: I should clarify that I need to use WriteableBitmapEx. – Christopher Tan Feb 02 '20 at 14:04
Nevermind, I figured out that it uses Format32bppArgb; makes sense since I saw on the WriteableBitmapEx website that it uses 32 bit color. – Christopher Tan Feb 02 '20 at 14:10
"type or namespace name Bitmap does not exist" in my out-of-the-box Wpf app project. No "using" suggested by Visual Studio 2022. EDIT: Visual Studio suggested the right import after I removed "System.Drawing" before Bitmap :-D – jeancallisti May 09 '22 at 16:06

How do I write text on WriteableBitmap?

1 Answers1