Question

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How to render bitmap into canvas in WPF?

What I want is simple. I want to place a BitmapImage into a Canvas in C#. My app is based on WPF. I searched for this and I found similar questions, but I could not find what I’m looking for.

In short, I have this:

BitmapImage img = new BitmapImage(new Uri("c:\\xyz.jpg"));

And I want to put this in the canvas, the mean is not that important, it can be a rectangle or whatever.

Answer 1

A BitmapImage object cannot be positioned inside a Canvas because it’s not a control. What you can do is to derive your own class from the Canvas and override the OnRender() method to draw your bitmap. Basically something like this:

class CanvasWithBitmap : Canvas
{
    public CanvasWithBitmap()
    {
        _image = new BitmapImage(new Uri(@"c:\xyz.jpg"));
    }

    protected override void OnRender(DrawingContext dc)
    {
        dc.DrawImage(_image,
            new Rect(0, 0, _image.PixelWidth, _image.PixelHeight));
    }

    private BitmapImage _image;
}

Of course you may need to expose the file path and coordinates inside the Canvas through properties. If you do not want to declare your own class just to draw a bitmap then you can’t use the BitmapImage class directly. The control to display images is Image, let’s try this:

BitmapImage bitmap = new BitmapImage();
bitmap.BeginInit();
bitmap.UriSource = new Uri(@"c:\xyz.jpg");
bitmap.EndInit();

Image image = new Image();
image.Source = bitmap;

Now you can put the Image control where you want inside the Canvas.